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Vacuum Extraction 

  • Author: John P O'Grady, MD, MA; Chief Editor: Thomas Chih Cheng Peng, MD  more...
Updated: Jan 22, 2015

Introduction and History

This article reviews the clinical use of vacuum extractor (VE) delivery instruments in modern obstetric management. The limitations and risks of the VE are considered, as is the choice of delivery technique (VE vs forceps vs cesarean delivery) when labor ceases or other complications ensue.

Both forceps and the VE are in use as delivery instruments. In recent decades, the VE has progressively replaced forceps as the instrument of choice for many practitioners.[1, 2] Active controversy concerns if and when operative vaginal deliveries should be conducted and which instrument is the best to use in specific clinical settings.

VE has a long history. The initial applications of vacuum techniques in deliveries began in the 18th century, derived from the ancient technique of cupping. However, designing a vacuum-based instrument for obstetric use proved difficult. A successful extraction required the development of techniques for the transvaginal application of a cup to the fetal head (and occasionally, in premodern times, the buttocks) as a means to apply traction, and the ability to periodically reinforce the vacuum due to inevitable imperfections of the seal.

James Young Simpson, the Edinburgh professor of obstetrics already famous for his forceps design, introduced the first successful obstetric VE in 1849. His "air tractor" was most likely derived from breast pump and consisted of a metal syringe attached to a soft rubber cup. The device was placed against the fetal head, the syringe was evacuated, and traction was then applied to the neck at the base of the cup and the infant extracted. This device did prove marginally successful, but technical problems existed, illustrating the difficulties facing the inventors of such devices. The vacuum force was limited and replenishment was impossible after the initial evacuation of the syringe. Further, the device lacked a pelvic curve, limiting higher applications.

Simpson did not further develop his extractor, and vacuum techniques for obstetric purposes fell from clinical interest for many decades until the stainless steel cup vacuum device was developed and introduced into practice by Malmström in 1956. This device, although successful, never achieved popularity in the United States because of technical problems with the original design, the general lack of American experience with vacuum technique, case reports of severe fetal complications, and competition with the well-established tradition of forceps delivery. Although VE became widely popular in Europe, the technique was little used in the United States until after the early 1980s, following the introduction of a series of new instruments, including disposable soft-cup extractors, new rigid cup designs, and handheld vacuum pumps.

Despite the current popularity of VE, forceps are the instrument of choice for many older clinicians. This is because of medical conservatism and original training, higher success rates, and a presumption of improved speed and control of the birth process. Nonetheless, VE has gained popularity as it is seemingly easy to use, requires less anesthesia/analgesia, has lower maternal morbidity, and is commonly believed to be safe. Less fortunately, the importance of correct VE technique and of the potential risks of the procedure are less well recognized. Large differences are observed in the popularity of instrumental delivery and of the specific type of instrument used in varying parts of the United States. This reflects the biases introduced by original training, the inherent conservatism of practitioners in embracing different techniques, and the absence of fixed guidelines for instrumentation.[3]

The retirement of classically trained obstetricians, the inability to conduct training operations (which is now partially offset by new training models), the medical-legal climate, and other changes in practice (including the high incidence of cesarean deliveries) result in an unclear future for all types of instrumental delivery, including VE. Finding clear answers to important management questions concerning instrumental delivery remains elusive. A great deal of traditional lore concerning delivery practices remains. Objective analysis of what constitutes best practice by the newer methods of evidence-based medicine is limited by continuous changes in practice, small patient numbers in many studies, changes in the official definition of procedures, and, especially for VE, the introduction of new instruments.

Despite these limitations, a need still remains for delivery assistance. Further, good data suggest that this help can be safely and expeditiously provided by an instrumental delivery using either the forceps or a VE instrument.[4, 5, 6]

The clinician's must understand the potential indications and contraindications to instrumental delivery, choose cases carefully, counsel parturients appropriately in the risks and benefits to assisted delivery, and choose an appropriate instrument and conduct with the operation with care.

For related information, see Medscape's Pregnancy Resource Center.


Prerequisites for Vacuum Extraction

Both forceps and vacuum extraction (VE) operations have essentially the same indications. In certain clinical settings, one type of instrument is better suited for use, but operator experience and established skill play an important role in the instrument chosen. The prerequisites for all types of instrumental delivery are discussed below.

Informed consent

Informed consent is required for any surgical procedure, including an instrumental delivery. Informed consent is a process and not simply a signed form. The question becomes the content of the discussion.

Consent for an instrumental delivery, especially in the face of urgency, has always been problematic and is often incomplete.[7] This has always been a curious feature of obstetric management, as the potential for maternal or fetal injury in VE or forceps operations is always present. Further, the medical and legal risks from an assisted delivery are substantially greater than those associated with many other surgical procedures.

Routinely discussing possible obstetric interventions with families at an earlier time during the pregnancy as part of routine prenatal care is important because of the controversy concerning bedside consents in acute situations. When antepartum discussions have occurred and the need for an instrumental delivery procedure occurs during labor, misunderstandings are reduced.

In general, consent for a surgical procedure requires the following:

  • An explanation of the need for the operation
  • A discussion of risks and benefits
  • A presentation of alternative modes of treatment
  • An opportunity to ask questions

An emergent or abbreviated bedside consent process still requires the following:

  • A (brief) description of the proposed operation to mother and family
  • Review of the indications for the proposed procedure
  • An indication of the limits of effort intended

Prepared physician

The clinician must have knowledge of the instrument chosen, VE indications, and well-practiced, appropriate technique. The decision to perform instrumentation should follow a

logical progression involving an analysis of the course in labor, a pelvic examination with determination of fetal position and station, and a careful consideration of the fetal/pelvic relationship. Most importantly, the accoucheur must be prepared to reconsider or abandon any operation that proves difficult. In the uncommon situation that a true trial of instrumental delivery is contemplated, the obstetric team must understand the plan of management, the limits of intended effort, and the possibility of cesarean delivery.

Prepared patient

The initial requirement is always informed consent. Thereafter, and prior to an extraction attempt, the surgeon must be certain that the parturient has ruptured membranes, an empty bladder by Credé, catheterization, or spontaneous voiding; full cervix dilation; and an engaged fetal head. Finally, fetopelvic disproportion cannot be suspected.

If the fetal position or the station of the presenting part is uncertain, a transperineal or transvaginal real time ultrasonographic examination is performed before attempting the operation.[8] Ultrasonography can also be used to judge the appropriateness of the vacuum cup application.[9, 10] These procedures are easily performed at the bedside. Position is readily identified by observing the fetal orbits and identifying characteristic intracranial anatomy (falx, posterior fossa, etc) and the location of the fetal spine. Station has been reported to be accurately estimated by translabial scanning but this determination involves a more complex technique.

Acceptable analgesia/anesthesia

Some outlet operative VE deliveries can be conducted without anesthesia or analgesia in multiparous patients. However, parturients do find operative vaginal procedures uncomfortable. Usually, either a regional anesthetic (eg, pudendal block) or, more frequently (and more effectively), a conduction anesthetic (eg, epidural, spinal, saddle block) is required.


Indications for Vacuum Extraction

General comments

The appropriate indications for operative delivery by either forceps or VE are those described by the American Congress of Obstetricians and Gynecologists in a practice bulletin.[6] Clinical judgement is necessary in the interpretation of potential indications because alternatives are available. If an instrumental delivery is not performed, the practitioner may recommend allowing the labor to proceed under close observation or, alternatively, conduct a cesarean delivery.

Prolonged second stage of labor

An extended second stage of labor is a relative, but not absolute, indication for an instrumental delivery. Clinical studies of second-stage length and maternal and fetal morbidity are complicated by the limitations of retrospective analysis using different criterion in differing populations.[11] From a review of the available data, an appropriate conclusion is that the longer the second stage, the lower the probability of spontaneous vaginal delivery, and the higher the risk of instrumentation or cesarean delivery.[12, 13, 14, 15, 16] Not surprisingly, obstetrical trauma such as postpartum hemorrhage, chorioamnionitis, and perineal injury become more likely as the second stage is extended. The situation for the neonate is less clear, but some increase in overall morbidity is probable. The data suggest that the magnitude of the maternal risk is greater than that for the infant, assuming proper maternal and fetal monitoring.

The definition of a prolonged second stage depends on parity and epidural anesthesia.[6] In general, second stages of more than 2 hours without epidural anesthesia and 3 hours with were the acceptable measures for nulliparas. One hour less in each category was the limit for multiparas. Intervention is not mandatory precisely at the classical second stage intervals. However, at those times, close reevaluation is mandatory.[17]

Continued poor progress in labor is not to be ignored. Failure to progress is the most common indication for intervention by a cesarean or an instrumental delivery.

Delayed second-stage progress usually results from a complex mix of poor or incoordinate uterine activity combined with subtle degrees of cranial deflection or other mild malpresentations. Fetal malpositioning, including cranial deflection, an occiput posterior or another uncommon presentation, or true fetopelvic disproportion could be present. Large infants are increasingly another factor. That a combination of features extending beyond simple pelvic capacity is the most frequent cause of labor dystocia is supported by the fact that when trials of vaginal birth after cesarean delivery (VBAC) are attempted, success rates are in the range of 60-70%, even when the indication for the initial surgery was failure to progress.[18] As absolute disproportion is now rare, poor progress is thus a reasonable indication for a trial of judicious oxytocin stimulation, assuming an acceptable examination and maternal/fetal stability.

The classic limitations to second-stage length constitute important markers for stopping and

reconsideration of the progress of the labor. If maternal/fetal condition is good, and the fetopelvic relationship is reasonable, encouragement and oxytocin are offered. If progress resumes after oxytocin is administered, observation is the best management. If the maternal and fetal condition remain good, and the clinician believes that vaginal delivery is reasonably probable, the second stage can be extended.

Yet, as time passes, the clinician must understand the declining probability of vaginal delivery and a slowly progressive risk of maternal complication. However, persistence is reasonable so long as success is likely. If progress stops, the mother is unable to continue, or the fetal or pelvic evaluation is questionable, a spontaneous vaginal delivery is no longer an option and the clinician needs to decide on a different mode of delivery and perform either a cesarean delivery or an instrumental assist.

Shortening of the second stage of labor

On occasion, elective shortening of the second stage of labor is required. In some maternal disorders (eg, cardiac, cerebrovascular, or neuromuscular), normal voluntary expulsive efforts by the mother are either contraindicated or impossible. Additional situations that might lead to intervention include maternal exhaustion following a long labor or, possibly, overly dense epidural analgesia. The indication of maternal exhaustion should be used with caution. This is a subjective determination. Maternal fatigue is often responsive to rest, rehydration, positional changes, and encouragement. Also, in selected cases, the intensity of analgesia/anesthesia can be modified to provide relief and oxytocin stimulation may result in a resumption of descent/dilatation.

Suspicion of immediate or potential fetal compromise

The suspicion of immediate or potential fetal compromise (eg, presumed fetal jeopardy, acutely

nonreassuring electronic fetal monitoring tracing) is a classic indication for either an operative or a cesarean delivery. This is exactly the setting in which extra caution is indicated. Proper case choice is not easy because current methods of fetal surveillance by electronic fetal monitoring are imprecise and the accurate diagnosis of immediate fetal jeopardy is often elusive, except in extreme instances such as fixed bradycardias or when electronic monitoring tracings document absent variability with decelerations.

When prompt delivery is necessary, the station and position of the fetal head, the fetopelvic relationship, operator skill, and a judgment of the severity of risk dictate the mode of delivery. In most cases, cord prolapse, abruptio placentae, or persistent bradycardia at a high station, even with full dilation with an engaged head are best managed by a cesarean delivery.

Nonetheless, expedited vaginal delivery using either VE or forceps is reasonable management in selected cases. Such instances usually involve a rapidly progressing labor when the maternal pelvis is adequate, the infant is normally presenting, the parturient is willing and able to assist, and an experienced obstetrician is present. However, bitter experience suggests that a successful and atraumatic rapid vaginal instrumental delivery is never guaranteed, except in retrospect. The risk of an unanticipated vaginal breech should be recalled: Achieving a vaginal delivery in such cases is either awfully simple or simply awful. Thus, choice of case is critical and emergency applications of either the forceps or a vacuum extractor are best conducted as trials, as described below.

Trials of instrumental delivery

Estimating the success in any attempted instrumental vaginal delivery is difficult. In this sense all instrumental deliveries are trials. The problems and controversy ensue in situations when the clinician believes that an attempt at assisted vaginal delivery is reasonable but the outcome involves more than the usual degree of uncertainty. The literature on this specific point is problematic and incomplete.[19, 20, 21] The important issues include how such cases are initially evaluated, the approach taken to recognized trials, and the approach in situations in which success is anticipated but does not occur. A resort to cesarean delivery if an extraction effort does not proceed easily simply reflects the limitations of clinical prediction. The cardinal admonition during all instrument deliveries, whether identified as trials or not, is not to doggedly persist in the face of failure or poor progress. Heroic vaginal operations have no place in modern obstetric management.

The authors define a trial of instrumental delivery as an obstetric operation in which delivery is indicated and the vaginal route is considered to be possible, but the outcome is judged uncertain. Although all instrumental delivery efforts include an element of uncertainty, a trial procedure is specifically characterized by simultaneous preparations for a cesarean if the vaginal procedure does not proceed rapidly and easily. Trials organized in this fashion are infrequent.

In a failed instrumental delivery, the surgeon anticipated success, but no concomitant preparations for alternative delivery have been made. The setting for these cases is often a labor or labor-delivery-recovery-postpartum (LDRP) room. In such instances, the greatest discipline is necessary to stop when progress is poor and avoid attempting to overcome relative or perhaps true disproportion by multiple efforts, increasing force, or the resort to a different instrument.

In the authors' view, a trial of instrumental delivery differs from a failed procedure. Unfortunately, the literature on this subject does not always adequately distinguish between these approaches. The senior author has conducted many trial procedures over a long clinical career and is convinced that a role remains for this approach when properly conducted. The recent paper by Alexander and coworkers supports this position.[22]

If a trial is contemplated, the initial step is a careful discussion with the parturient/family with a review of the proposed procedure and the limits of effort intended. Then, the following steps are appropriate:

  • The most experienced clinician remains at the perineum, while maternal bearing down efforts are actively recruited (as appropriate, observing electronic fetal monitoring [EFM] or noting fetal heart rate [FHR] ausculatory data).
  • Other personnel simultaneously prepare for a cesarean delivery.
  • The operation is mentally reviewed by the surgeon and the limits of effort considered.
  • The chosen instrument is inserted, and the application is checked.
  • Traction is applied during a contraction, paralleling maternal bearing-down efforts.
  • If the operation does not proceed easily and promptly with rapid descent of the presenting part, the attempt is abandoned. The presenting part is then displaced upward, the patient's legs are drawn down, and a cesarean delivery is performed.

Contraindications to Vacuum Extraction

Vacuum operations are contraindicated in certain settings. Neither the vacuum not the forceps should be applied where the fetal risk is either unknown or perceived to be high, or when the application proves difficult or the maternal pelvic anatomy is questionable. Questions of operator skill and experience in that specific clinical setting are also noted.

General contraindications include the following:

  • Operator inexperience
  • Inability to achieve a correct application (midline, over flexion point)
  • An inadequate trial of labor or lack of a standard indication
  • Uncertainty concerning fetal position or station not resolved by examination or real-time ultrasound study
  • Suspicion of fetopelvic disproportion (advanced cranial molding, bone overlap, caput)
  • An inappropriate fetal presentation (eg, breech, face, brow)
  • A known or suspected fetal bleeding diathesis or demineralizing bone disease

Relative contraindications are as follows:

  • Prematurity: When the fetus is less than 36 weeks' gestation, vacuum extraction (VE) applications are not recommended. Some authors prefer a 34 week limit. The magnitude of risk is not known with certainty, as no specific data guide management. The physics of grasping the fetal scalp by the vacuum cup and the known fragility of intracranial vascular structures in the premature infant mitigate against applications in the preterm unless special circumstances are present. This issue is reviewed in greater detail below.
  • Prior scalp sampling: Scalp sampling is now an uncommon procedure. A prior sampling is not normally a problem in a VE operation. In very unusual circumstances, fetal bleeding has occurred with VE after scalp sampling, leading to either extra blood loss or a cephalohematoma. The risk is remote, at best. Prior application of a scalp electrode does not preclude VE use.
  • Prior failed forceps: Prior unsuccessful application and traction with forceps is usually a contraindication to any VE effort. Serial instrumentation is discussed in more detail below. As a practical matter, the forceps can generate more traction force than the VE. Thus, to follow a forceps effort with a VE trial is not inherently reasonable unless circumstances have prevented the successful application of a forceps before traction has been attempted or other special features apply. An example might be the inability to achieve (or properly verify) an appropriate forceps application after blade insertion. Such cases must be quite unusual and should prompt immediate caution as heavy cranial molding and advanced caput (both harbingers of disproportion) are likely to be present.
  • Overlapping cranial bones, heavy caput: Overlap of cranial bones, the inability to palpate the standard landmarks, and cranial edema (caput/cephalohematoma) are markers of advanced cranial molding, suggestive of at least relative disproportion. When these findings are combined with poor progress, the clinician may find that the presenting part is substantially higher than initially anticipated. Advanced molding can bring the presenting part nearly to the introitus while the biparietal diameter remains much higher in the pelvis. True disproportion may be present, precluding any vaginal trial. The bedside evaluation of such cases with real-time ultrasonographic scanning can be of particular assistance in determining position and, to a lesser degree, station. [8] In all these cases, any attempt at instrumental delivery must proceed with caution if it is attempted at all.
  • Known or suspected fetal macrosomia: A large infant (estimated fetal weight >4,250-4,500 g in a nondiabetic) is as a relative contraindication to instrumental delivery. [23, 24] This is primarily because methods of estimation of fetal bulk are inaccurate. Although ultrasonographic scanning is often used for weight estimates at or near-term, in most cases, such estimates are considered as ± 6-12%, with only 40-75% of these estimates falling within 10% of actual birth weight. Ultrasonographic data should not be used as the sole means for estimation of fetal bulk or for making obstetric management decisions. This information is only useful when combined with other information that dynamically evaluates the fetopelvic relationship (eg, Muller-Hillis maneuver, overlap of cranial bones, course in labor, pelvimetry).
  • In retrospective studies, a clear association between large infants and an increased risk of intrapartum injury is noted; although the long-term rate of persisting injury remains low. [23, 24]


The American Congress of Obstetricians and Gynecologists (ACOG) has established standard definitions for instrumental delivery operations. These include outlet, low, and midpelvic operations. Coding depends on the clinical assessment of fetal position and station immediately prior to initiating an operation. While the guidelines were originally written for forceps procedures, the same descriptions are easily applied to vacuum extraction operations with minor modifications.[6]

Table 1. Proposed Classification for Vacuum Extraction Procedures According to Fetal Station and Cranial Position (modified from ACOG Practice Bulletin # 17, June, 2000) (Open Table in a new window)

Type of Procedure Description of Classification *
Outlet-vacuum operation The fetal head is at or on the perineum; the scalp is visible at the introitus without separating the labia; the fetal skull has reached the pelvic floor. The sagittal suture is in the AP diameter (ROA, LOA, OA) or posterior (ROP, LOP, OP) position.
Low-vacuum operation The position/station of the fetal head does not fulfill the criterion for an outlet operation; the leading edge of the fetal skull is at station +2/5 cm, but has not reached the pelvic floor.†
Subdivisions (a) Position is occiput anterior (OA, LOA, ROA).

(b) Position is occiput posterior (OP, LOP, ROP) or transverse (LOT, ROT).

Midvacuum operation Station
Subdivisions (a) Position is occiput anterior (OA, LOA, ROA).

(b) Position is occiput posterior (OP, LOP, ROP) or transverse (LOT, ROT).

Vacuum-assisted cesarean delivery This includes all vacuum-assisted cesarean deliveries, unspecified technique.
Special vacuum operations This includes vacuum extraction operations not otherwise specified; full details are described in the dictated operative note.
High-vacuum operation Such procedures are not included in the classification.
OA: occipitoanterior; ROA: right occipitoanterior; LOA: left occipitoanterior; OP: occipitoposterior; LOP: left occipitoposterior; ROP: right occipitoposterior; LOT: left occipitotransverse; ROT: right occipitotransverse

*The type of operation coded in the medical record is determined by pelvic examination noting the position and station of the fetal head at the time the extraction is initiated.

†To standardize nomenclature, especially as other methods were used in the past, the authors recommend the ACOG ±5 cm system for the reporting of station, with certain modifications. Station (recorded as +5 to –5 cm) is defined as the distance in centimeters from the leading bony portion of the fetal skull to the imaginary plane of the maternal ischial spines. In the authors’ practice, they determine station by first conducting a pelvic examination, noting the distance from the presenting part to the ischial spines. This number is then entered into the medical record, followed by a notation specifying the technique used for reporting. Thus, if the clinician's estimate is that the bony presenting part is 2 cm below the plane of the ischial spines, a station of +2/5 cm is recorded.

Note that formal dictation of all vacuum operations is recommended, regardless of the apparent ease of the procedure or the initial condition of the neonate.


Design of the Vacuum Extractor

Vacuum extraction instruments

Vacuum extraction (VE) instruments are constructed of varying materials including polyethylene or silastic plastic and stainless steel. Several features are found in all designs. These include the following:

  • A mushroom-shaped vacuum cup of varying composition, diameter, and depth
  • A fixed internal vacuum grid or guard within the vacuum cup
  • A combined vacuum pump / handle or a vacuum port for a vacuum hose attachment
  • A handle for traction

Rigid-cup designs include the classic Malmström stainless steel vacuum cup and the various modifications of this instrument introduced since the 1960s. New rigid plastic cup extractors mimic the Malmström device. These were originally designed for use with deflexed or posterior positioned heads but now are becoming popular for all types of deliveries.[25] A recent trend in VE design is to incorporate the vacuum pump within the handle, avoiding the need for a separate vacuum tube and for the assistance of a birth attendant in producing vacuum.

The soft-cup extractors include numerous disposable polyethylene or combined polyethylene-silastic cup designs that differ in largely inconsequential and clinically unimportant ways.

Comparison of instruments

Soft or flexible vacuum cups have a higher incidence of failure than either rigid vacuum cups (plastic or metal) or forceps.[26] This is primarily due to their higher frequency of spontaneous detachment pop-offs. However, the application of soft vacuum cups also results in less fetal cosmetic injury (principally scalp injury) than rigid cups. This partially reflects the inability of soft cups to generate the same degree of scalp traction as is possible when rigid cups are applied.

Other design issues are important to cup choice. In some plastic extractor designs, the relatively rigid tube connecting the handle to the cup precludes accurate placement of the instrument when the fetal head is markedly deflexed or occiput posterior. This contributes to failure when such cranial malpositions are present. Higher success rates have recently been reported when rigid plastic cups similar to the original Malmström design are used for such deflexed and posterior presentations


Vacuum Extraction Technique

Appropriate technique is important when the vacuum extraction (VE) is used.[17, 27, 28, 29] The safety and success of vacuum-conducted extraction operations depend on the following:

  • The accuracy of the initial cup application (ie, cup center over flexion or pivot-point)
  • Case choice
  • The traction technique, including degree of effort (number of tractions), vector of traction, method of applied force
  • The fetal cranial position (including deflection) and fetal station at the time of application
  • The cup design
  • The fetopelvic relationship

If the prerequisites for VE operation are met, informed consent is obtained. Thereafter, the position, station, and attitude of the fetal head are verified by pelvic examination and an instrument is chosen. To correctly insert and position the cup, a specific protocol is followed.[17, 27]


A ghost or phantom application is first performed. This step is mandatory (see the image below).

Ghosting or phantom application of vacuum extracti Ghosting or phantom application of vacuum extraction.

In ghosting, the surgeon holds the vacuum cup in front of the perineum in the same angle and position expected once the extractor has correctly been applied to the fetal head. This is an exact parallel to the ghosting or phantom application procedure classically taught for forceps operative deliveries. The phantom application forces the clinician to make an additional check of fetal position and fetal station and establishes the correct instrument orientation. It also imposes a brief pause in the procedure, that should be used by the surgeon to mentally review the conduct of the planned operation. If uncertainty exists concerning the position, station, or flexion of the presenting part, a pelvic examination is repeated or an abdominal and/or transperineal real-time ultrasonographic scan is performed prior to applying the instrument.

Insertion: The cup is lubricated with sterile lubricant or surgical soap. If a soft cup is used, it may be partially collapsed by the operator's hand and introduced through the labia. Rigid cups are turned sideways, the labia are gently spread, and the device is slipped into the vagina and then positioned against the fetal head.

Correct application

Once what is believed to be a proper cup application is established, sufficient vacuum (100-150 mm Hg) to fix the cup to the fetal head is applied. A check of cup placement follows (ie, mid sagittal, over pivot point, no maternal tissue included).

The cup must be applied so that the vector of traction is directed through the cranial pivot point. A properly applied cup flexes but neither twists obliquely nor extends the head as force is applied. Anatomically, the pivot point is an imaginary spot over the sagittal suture of the fetal skull, located approximately 6 cm posterior to the center of the anterior fontanel or 1-2 cm anterior to the posterior fontanel. When properly placed with its center over the pivot point, the edge of a standard 60-mm cup lies approximately 3 cm or 2 fingerbreadths behind the center of the anterior fontanel in the midline over the sagittal suture (see the image below).

Cranial flexion or pivot point. Cranial flexion or pivot point.

In VE operations, the anterior fontanel becomes the principal reference point for checking the instrument application. Access to the posterior fontanel is usually partially blocked once the extractor cup is correctly placed, rendering this familiar landmark unusable. The further the cup center is displaced from the cranial pivot or flexion point, the greater the failure rate. Traction with an oblique application results in progressive cranial deflexion or twisting (see the image below).

Incorrect sites for cup placement. Incorrect sites for cup placement.

This actually increases the work of the extraction by presenting an ever larger cranial diameter to the birth canal.[27]

Note that real-time ultrasonography has been successfully used to verify the station and position of the fetal head as to determine correct cup placement.[10, 8, 30]


Once the surgeon has verified cup placement, full vacuum is applied (450-600 mm Hg) and traction follows, paralleling the uterine contractions. With modern plastic cups, waiting an arbitrary period of time for a chignon to form is not necessary.[31] The direction of pull on the traction handle changes as the fetal head transverses the pelvic curve (see the images below).

Changing vector of traction. Changing vector of traction.
Lateral view of maternal pelvis. Pelvic axis/curve Lateral view of maternal pelvis. Pelvic axis/curve is demonstrated.

Traction efforts are timed to coincide with uterine contractions. Once the contraction begins, the vacuum pump is actuated until the appropriate degree of vacuum pressure is reached. Traction by the surgeon follows, with the force applied to the extractor handle gradually increased to the desired level, paralleling the rise in uterine force generated by the contraction.

As force is applied, the surgeon and other birth attendants recruit maternal bearing down efforts. As each contraction wanes, the tension on the extractor handle is relaxed. Attempting traction without the assistance of maternal bearing down efforts and/or a uterine contraction is inappropriate. These techniques simply predispose to failure and risk a fetal scalp injury from a pop-off.

In the relaxation phase between contractions, the vacuum can either be maintained or reduced to less than 200 mm Hg. Both techniques are acceptable. Continuous vacuum throughout the procedure and intermittent vacuum with the vacuum released between contractions, have been studied in a randomized trial.[32] No differences between groups are noted with regard to the speed of delivery, rates of instrument failure, or maternal or fetal outcomes. Thus, the use of either technique is at the discretion of the surgeon. The authors favor vacuum reduction.

A 2012 Cochrane review examined the safety and efficacy of rapid versus stepwise negative pressure application for vacuum extraction. The authors found that rapid negative pressure application reduces the duration of vacuum extraction without affecting maternal or neonatal outcomes.[33]

During traction, the surgeon should place the nondominant hand within the vagina, with the thumb on the extractor cup and one or more fingers on the fetal scalp. So positioned, the accoucheur follows the descent of the presenting part and can judge the appropriate and changing angle for traction while gauging the relative position of the cup edge to the scalp. This helps to detect cup separation. The vector of traction is in the curve of Carus (pelvic curve). The initial angle for traction depends on the station but is usually downward, then progressively extending upward as the head emerges. Once the head has been extracted, the vacuum pressure is relieved, the cup removed and the usual techniques to complete the delivery are followed.

Jerking motions and oblique pulls are best avoided as they risk cup displacement. The ventouse is not a rotating instrument. Attempts at cup rotation to assist cranial rotation simply foster cup displacement, loss of station, or scalp injury. Under traction, the fetal head usually rotates automatically as descent occurs. If the clinician feels an obligation to assist or hasten this process, then manual rotation of the head (not the cup) by one or more fingers can accompany the extraction. Normally, this is not required. Efforts at rotation should never be forced.

An episiotomy is not recommended as a routine measure during a VE operation unless the soft tissue impedes the descent of the presenting part. Incising the perineum predisposes to extensions into the underlying tissues including the rectal sphincter, increasing morbidity.

Ideally, descent of the presenting part should begin with the initial traction effort, assuming proper coordination with the maternal bearing down efforts and the uterine contractions. If the operator is uncertain that descent has occurred, a maximum of 2 additional tractions may be attempted.[34] The failure to clearly achieve fetal station after properly timed traction in the correct vector of force mandates prompt reassessment of the procedure both in terms of technique and desirability. Recurrent tensioning of the scalp without descent of the presenting part (negative traction) predisposes to cup pop-offs and is believed to increase the risk for scalp injury.

Limits to effort

Numerous aspects of best practice in the use of the ventouse are not established. The most important are (1) the number of acceptable unintended cup displacements (pop-offs) permissible and (2) the number of appropriate tractions and as a related matter the upper limits of traction force that should be used.

In terms of the traction force required for delivery, recent studies suggest that the large

majority of extractions are successful with a total applied force of 11.5 kg (25 lbs or less).[35, 36] Baskett's review of 1000 consecutive extraction operations noted that 25 lbs of traction force or less was required in 85.7% of cases using the OmniCup device.

When the number of popoffs or the acceptable number of total tractions efforts are considered, the literature is simply inconsistent. The clinician is left to consider the opinions of various authors and the reports from several series when certain protocols of usage were followed. In terms of traction number, studies performed with forceps and rigid-cup extractors have consistent findings. In approximately 85% of births, seemingly independent of whether the delivery is via forceps or the VE, the delivery occurs with 4 or fewer tractions.[35, 37, 38] No changes in the overall statistics as reported by Sjostedt in 1967 have occurred. As an example, in Baskett's 2008 review of 1000 cases 3 or fewer pulls were required in 95.6% of the successful procedures.[35]

Table 2. Number of Tractions Required in Vacuum Extraction and Forceps Deliveries* (Open Table in a new window)

Number of Traction Efforts Successful Malmström Vacuum Extractor Deliveries (n=433) Successful Forceps Deliveries† (n=555)
1-2 296 (68.4%) 213 (38.4%)


108 (24.9%) 270 (48.6%)
≥5 29 (6.7%) 72 (12.9%)
* Breech, cesarean delivery, and transverse lies, are excluded.[38]

Type unspecified


The upper number of acceptable popoffs is similarly not established. Clinical experience indicates that more than 2 pop-offs is sufficient, especially if progress has been minimal and the cup application and traction technique were proper. However, the correct number is not established.

When the upper limit of effort in vacuum assisted deliveries is considered, the rules of reasonable behavior must apply. If progress has been consistent and cranial delivery is imminent, abandoning a procedure in favor of a cesarean delivery simply because the third or fourth pull has occurred is inappropriate. In contrast, procedures leading to cup pop-offs or procedures requiring multiple traction efforts with limited progress are clearly best abandoned.

Optimistic beliefs in continued but very slow progress usually represent no progress at all. As the accoucheur strains to overcome what is usually a degree of disproportion, he or she is easily tempted to try just one more traction (or several more). More dangerously, the clinician may abandon the original VE effort without considering why there has been tardy progress and subsequently apply a forceps in the determined effort to achieve a vaginal delivery. Multiple tractions and instrument applications after poor or limited progress represent a failure in decision making.

When the case does not go easily, the correct answer is to stop. In Baskett's report, the VE was successful in 87% of 1000 consecutive cases. When successful, 97.4% of the VE procedures took 10 minutes or less, and 95.6% involved 3 or fewer tractions.

Special applications

No data suggest any specific advantage to VE over forceps or the vectis blade (Murless instrument) for instrumental extractions during a cesarean delivery. Information concerning potential risks and benefits of these procedures are nonexistent. The application of a VE during a cesarean delivery presents a question of practicality. While uncommon, fetal injury is possible during these operations so they must be performed with the same degree of care as transvaginal procedures.[39]

In general, deeply engaged fetal heads are best elevated from below by an assistant and then delivered primarily by manual extraction. This may obviate the need for the application of any instrument. On occasion, a vectis blade (Murless extractor) is useful in just this circumstance. However, if during a cesarean delivery a thin or friable lower-uterine segment is combined with a narrow or deep pelvis, myometrial lacerations such as an extensionsof the original incision are frequent when a manual extraction of the fetal head is performed. Also, a fetus in a high transverse lie or the second of twins may also prove difficult to extract during a cesarean delivery without uterine relaxation, upward extension of the original incision, or substantial traction. In these settings, either a forceps or the VE are occasionally applied. The fetal head is manipulated into the uterine incision. The VE then grasps the fetal head, and the subsequent extraction is usually easy.

Thus, the author does not favor the use of the vacuum extractor routinely at cesarean

delivery but restricts use to several unique obstetric settings in which the benefits of the

extractor arguably outweigh the potential risk when alternative methods of management are considered.

Sequential instrument use

Recent studies by Gardella[40] and Towner[41] involving large numbers of cases report that sequential operations (vacuum extraction/forceps) are associated with an increased risk for fetal intracranial hemorrhage (ICH), exceeding the risk when either forceps or VE are used alone. Similar data concerning an enhanced risk from combined procedures comes from review of the 1998 Food and Drug Administration (FDA) advisory paper on VE,[42] as well as other sources. However, this has not been the finding in all series.[43] Additional discussion of intracranial injuries and instrumental delivery occurs in Choice of Instrument.

Injuries from multiple instrument use are most likely when a degree of unrecognized fetopelvic disproportion is present and, despite difficulty, the clinician cannot refrain from pursuing a vaginal operative delivery. The authors believe that the risk is one of degree. When one type of instrument is applied and fails, no absolute prohibition exists to trying a different device. However, limiting effort and case choice are critical. Any failure of an original VE or forceps procedure must immediately suggest relative disproportion or faulty technique. In today's obstetrics, difficulty in delivery should inspire immediate caution and reassessment, not the resolve to triumph over difficulty by additional traction efforts or the application of a different instrument

In some cases, changing the delivery instruments can constitute good management. These include those in which technical problems, such as a malfunctioning hand pump, a misapplied vacuum cup, or traction in the incorrect vector of force, are believed to be the cause of failure. The least desirable cases are those in which traction without progress or multiple pop-offs occur following a correct application of the vacuum extractor and appropriate traction.

Operative vaginal deliveries in which one type of instrument is applied after the failure of another (such as an effort at vacuum extraction following an unsuccessful trial of forceps or, more commonly, the application of forceps following a failed vacuum extraction) must not be routine. Only the most experienced of accoucheurs should consider reapplications. For most obstetric surgeons, the failure of a properly applied delivery instrument should be followed by a prompt cesarean delivery.

Prophylactic antibiotics

Traditionally, antibiotics have not been administered for the sole indication of an instrumental delivery either with the VE or forceps. No compelling data suggest that prophylactic treatment is appropriate.[44] Antibiotics should be administered to women during labor/parturition following the usual obstetric indications and not specifically for an instrumental delivery.


Vacuum extraction is potentially associated with delayed complications in neonates that might later be associated rightly or wrongly to the events of parturition. Especially in reference to all obstetric manipulations, full reporting in the medical record is prudent.

Preoperative note includes the following:

  • Intentions of the surgeon/limits of effort intended
  • Clinical setting
  • Discussion of consent process
  • Complemented by a detailed post procedure note

Surgical operation documentation is as follows:

  • Parallel the documentation practices for other surgical procedure; either dictate the procedure or use a computer template
  • For dictations, follow the institutional requirements for documentation (eg, preoperative/postoperative diagnoses, procedure, surgeons)

Contents of surgical note are as follows:

  • The indications for the operation/clinical setting that prompted intervention
  • Document that a consent process preceded the operation
  • Discuss maternal/fetal evaluations prior to the application of the instrument (eg, examination, Leopold, ultrasound)
  • Include standard prerequisites for vaginal delivery procedure present (eg, full dilation, engagement, bladder empty)
  • Record the station, position, and orientation of the fetal head
  • Report number of tractions and pop-offs (if any)
  • Total time of cup application
  • Report any complications (eg, maternal or fetal injuries) and their repair
  • Notifications that the pediatrician knows a VE has occurred
  • Report any other technical aspects of the procedure

Medical record is as follows:

  • If an obstetric program, card, or screen contains the information as listed above, an electronic record can replace the formal dictation

Birth Injuries

Neonatal injury

No assisted vaginal or cesarean delivery is entirely free of risk for mother and infant.[45, 46, 17, 47, 29] Important issues to consider include the magnitude of this risk and choices in procedures or techniques that might reduce risk once the natural processes of labor fail or if delivery must be expedited for maternal or fetal indications. As risk is considered, it must be judged against an appropriate control group with a similar clinical status and compared with an appropriate alternative procedure.

The reported incidence of fetal death or severe fetal injury from vacuum extraction (VE) is low, ranging from 0.1-3 cases per 1,000 extraction procedures. The most common injuries are to the fetal scalp. Clinically diagnosed scalp injuries occur largely because of the physics of VE. As the vacuum force is applied, the extractor draws the fetal scalp into the body of the cup, with some variation depending upon cup design. This grasping of the scalp produces the characteristic mound of scalp tissue and edema, the chignon, that was classically noted after an extraction with a rigid Malmstrom type cup. When traction is applied for delivery, it also tensions the scalp against its attachments to the fetal skull, drawing it in the direction of the cup. Collectively, these effects predispose to bleeding within the scalp due largely to injury to small bridging veins.

The 2 major types of scalp injury associated with vacuum operations are the common, but clinically unimportant, cephalohematomas and the relatively rare, but potentially life-threatening, subgaleal hemorrhages (see the image below).

Scalp cross-section and hemorrhage sites. Scalp cross-section and hemorrhage sites.

Scalp bruising or lacerations and retinal hemorrhages are additional, usually insignificant fetal risks of extraction procedures.

When either radiographic or ultrasonic studies of the CNS are routinely performed on newborns who were delivered spontaneously or by instrumental assistance, minor trauma to the scalp, linear occult cranial fractures, and subarachnoid bleeding are discovered more frequently than are discovered by clinical signs and symptoms in the newborn.[48, 49] A small series by Whitby using MRI studies in term asymptomatic newborns reported similar findings.[50]

These observations and the difficulties in clinically distinguishing cephalohematomas from edema or in diagnosing small subgaleal bleeds indicate that investigations based solely on clinical presentation and physical examinations miss many asymptomatic neonates with some degree of birth-related trauma. The data also indicate that the large proportion of these asymptomatic events are not of clinical importance. Drawing from the Towner data, the major risk for these occult injuries is most likely labor and the cranial distortion normal in vaginal delivery.[41]

Subgaleal and subaponeurotic hemorrhage

The most feared complication of VE is hemorrhage into the subgaleal (SG) or subaponeurotic space from rupture of the emissary veins.[51, 52, 46, 27, 29] This condition is potentially life threatening, with a mortality rate in identified cases reported as high as 20%. Approximately half of all SG hemorrhages are related to the VE. Most of the rest are associated with forceps operations. Less commonly, SG bleeds follow spontaneous deliveries. The reported incidence of clinically identified or symptomatic SG hemorrhages ranges from 0-50 per 1,000 VE operations. Judging from the largest series with close attention to neonatal condition, the higher reported rates do not reflect the rates of injury in modern practice when strict protocols for application and the limitation of effort are followed.

Baskett in 1000 sequential VE operations reported one case of SG hemorrhage,[35] and Simonson and coworkers in a series of 1,123 reported none.[49] This is in contrast to the series of Boo (n= 338), who noted a SG incidence of 21% and an associated mortality of 2.8%[53] . Also, in the series of 1000 VE deliveries recorded by Ng,[52] SG hemorrhages were reported in 0.64%; however, paradoxically, the reported mortality rate in this series was


Of interest, SG bleeding was not observed in the large number of cases included in several major clinical reports in recent years.[34, 49] No SG cases were reported in the large VE meta-analysis by Johanson.[26] Also, in a report by Simonson et al, of 913 VE procedures, no instances of SG were reported in a study in which neonates were routinely screened postdelivery by cranial ultrasonography and radiography.[49] Further, the French study by Baume and coworkers involving 845 VE operations also did not report any clinically identified cases of SG hemorrhage.[34] These data document the rarity of such clinically significant severe scalp injuries when strict technical guidelines for the performance of VE operations are employed. Several atypical series aside, the best data from experienced practitioners indicates that the risk of symptomatic SG hemorrhage is quite small, although no clinician should ever assume that it is zero.

In the experience of the authors, SG bleeding is mostly likely when excessive force, multiple pop-offs, prolonged cup application times or serial instrumentation with VE and forceps has occurred. However, serious cases of SG and symptomatic intracranial bleeding have followed outwardly uneventful extractions, including those performed at cesarean delivery.[54, 39] Thus, even strict adherence to protocol may not avoid all cases and simple explanations for SG or intracranial hemorrhage need reconsideration. Because of the small but significant risk of SG bleeding, the attending pediatric personnel should be informed whenever a VE operation has occurred, regardless of the immediate condition of the neonate. SG hemorrhages are dangerous because the clinical signs and symptoms are often occult and insidious of onset. Clinically apparent difficulty may be delayed until some hours postpartum. Thus, serial observation is required.

Scalp bruising and lacerations

Ecchymoses and, uncommonly, scalp slough or lacerations can follow VE. Most of these injuries occur when the recommended 30-minute (some authors favor 20 minutes) limit to total cup application is exceeded or efforts are made at cup rotation (contraindicated). These injuries are now quite uncommon.

The ventouse is not a rotating instrument. Attempts at cup rotation to assist cranial rotation simply foster cup displacement, loss of station, or scalp injury. Under traction, the fetal head usually rotates automatically as descent occurs. If the clinician feels an obligation to assist or hasten this process, then manual rotation of the head (not the cup) by one or more fingers can accompany the extraction. Normally, this is not required. Efforts at rotation should never be forced.

Comments regarding risk

The risk from vacuum extraction operations arises from 2 basic sources: An inherent but small procedure-related risk independent of the operator, reflecting the physics of securing the fetal scalp and cranial traction. The far more important risk arising from the actual conduct of the operation (eg, traction to scalp, perineal pressure). This procedural or operative risk reflects the skill of the operator, the fetopelvic size relationship, the orientation of the fetal head, the resistance of the maternal soft tissues, and the station of the fetal head at the commencement of the operation, among other factors.

Importantly, these components of risk are subject to modification by the careful choice of cases, judicious use of traction in the appropriate vector of force, performance of episiotomy or not, and, most importantly, knowing when to desist from additional efforts if progress is not prompt. Most important, fetal injuries occur when multiple cup displacements occur, the extraction proves difficult or prolonged, multiple instruments are used, or a shoulder dystocia complicates the delivery.

The complications associated with instrumental delivery are essentially the same as occur during spontaneous vaginal delivery, but the incidence is higher. The reported incidence of complications is reportedly different in varying series depends on case choice, operator skill, refinement of technique, the instruments used, and other unknown factors.

As with all types of instrumental delivery, not all risks are eliminated by established protocol. However, vacuum operations are demonstrably as safe for the fetus as forceps procedures. Because of the unique method of grasping the fetal head, vacuum extraction has advantages verus forceps in terms of the risk of maternal injury and in applications when anesthesia is limited.

Long-term neonatal outcomes

Studies evaluating both the general safety and the long-term neurologic sequelae of instrumental delivery reported no important differences in outcome between children delivered spontaneously versus those delivered by either VE or forceps.[55, 56, 57, 47, 58, 49, 59] Cohorts of children delivered by VE-assisted procedures versus spontaneous deliveries have been studied at intervals of up to 18 years.[57, 56] These children scored similarly in scholastic performance, speech, ability for self-care, and neurologic status. These latter long-term studies, although limited in total patient number and subject to flaws in completeness, provide reassurance of VE safety.

Maternal injury

Vacuum extraction has a low rate of maternal injury in comparison with forceps operations or cesarean delivery. However, maternal injuries do occur. Such trauma cannot be disregarded in evaluating the risk of the procedure.[34]


Maternal perineal lacerations are common complications of all operative vaginal deliveries.[34] Most significant tears are associated with episiotomy. Depending on series reflecting obstetric routines of perineal management and instrument use, the incidence of severe perineal lacerations (ie, third-degree and fourth-degree lacerations) during VE procedures ranges from 5-30%. Women who sustain vaginal lacerations in a previous delivery are at a significantly greater risk for a repeat laceration in subsequent deliveries. Women at greatest risk are those who experienced a laceration in the first delivery followed by another delivery combining both an instrumental delivery and an episiotomy. Delivery technique, skill, fetal bulk, prior scars, and instrument choice are important factors in perineal injury.[60, 61, 62, 63, 64, 65, 66, 67, 2]

One area in which the vacuum extractor has a clear advantage over forceps is the incidence of perineal trauma. Forceps operations are more likely to result in anal sphincter injury trauma than vacuum extractions. As noted, episiotomy is an important risk factor. Electively incising the perineum predisposes to perineal lacerations and rectal injuries by direct extension. The authors favor the selective performance of episiotomy and only if maternal soft tissues impede the delivery process. In Europe, when an episiotomy is required, mediolateral (ML) incisions are often preferred. ML episiotomies are less likely than median episiotomies (ME) to extend into the rectal sphincter or mucosa.[63] However, the ML is harder to repair, is more likely to result in distortion of the perineum, and results in more pain during the puerperium.

Episiotomy should not be routine and careful technique can often avoid tears, especially in multiparas. Best practice concerning whether to perform an episiotomy during an instrumental delivery, the type to use, and the timing is yet to be established. In the author’s opinion, episiotomy is best avoided. If required, the type of perineal incision depends on the maternal anatomy and the station of the extraction effort.

Urinary and anal incontinence

Genetic predisposition, dystocia in labor, vaginal delivery, obstetric lacerations, multiparity, and the mode of delivery combine to result in both reversible and permanent injuries to connective tissues of the maternal pelvis. Injury to these support structures and to the rectum constitutes important and perhaps unavoidable risks of both labor and instrumental delivery.[68, 69, 61, 70, 71]

The female pelvic viscera are suspended from above and supported from below. The intactness of the various support structures depends upon the integrity of their muscular, fascial, and neurologic constituents. Parturition and assisted delivery both result in various injuries to these structures, not all of which are reversible.

The upper suspensory structures are a complex of pseudoligamentous structures loosely termed pelvic ligaments. This connective tissue accompanies vascular structures into the pelvis to surround the cervix. The lower supports for the uterus are a musculofascial complex including the urogenital and pelvic diaphragms. The pelvic diaphragm principally consists of the levator ani muscle. The urogenital diaphragm is a complex of small muscles and accompanying connective tissue that extends from the central perineal body radially to attach to various bony and ligamentous sites in the pelvis.

Both labor and the process of passing the fetal body through the birth canal distort and injure these and other pelvic tissues. During parturition, pelvic ligaments and muscles are either simply torn from their various attachments or are otherwise disrupted and the accompanying nerves are traumatized. Various spontaneous lacerations or episiotomy extensions account for additional injuries, especially to the internal and external rectal sphincters.

The issue is not whether vaginal delivery results in injuries to pelvic soft tissues. The question is the degree of the injury and the extent to which spontaneous postpartum healing or specific muscle strengthening exercises performed in the puerperium may ameliorate this damage. In terms of instrumental delivery, techniques that either reduce or avoid injury to pelvic supports and to the rectum are under study. Long-term, follow-up studies controlling for prepartum pelvic support status (eg, preexisting rectal dysfunction, urinary incontinence) as well as length of labor, type of anesthesia, clinically observed perineal trauma, and delivery method are required before changes in current practice can be confidently recommended.


Vacuum Extraction Versus Forceps

Forceps operations have become less popular, and vacuum extraction (VE) procedures are more common in recent years. There is long-term debate concerning when assisted delivery is appropriate and which instrument (vacuum extractor or forceps), is best.[72, 27, 73, 37, 5, 74, 47, 2, 17, 29] Although the instruments are largely interchangeable for most applications there are factors favoring the use of one instrument over the other. Important factors include the following:

  • Anesthesia: In general, low or outlet vacuum extraction (VE) operations are less uncomfortable for the mother than a forceps procedure from the same station. The meta-analysis reported by Johanson observed a significant reduction in the requirement for anesthesia with VE operations in comparison with forceps deliveries. [2] With a willing parturient, an uncomplicated VE can occasionally be performed with either a local, pudendal, or no anesthetic.
  • Instrument failure: VE operations are more likely to fail than forceps procedures. [20] The relative risk of failure with VE versus forceps operations is 1.69 (95% CI 1.31 to 2.19). The higher VE failure rate reflects a number of factors: poor instrument applications, incorrect vector of force in traction efforts, improper methods of applying traction, fetal malpositioning, poor choice of cases, and operator inexperience as well as the intrinsic inability of the vacuum extractor to exert as much force to the fetal head as forceps. [43, 75] The higher failure rate for VE operations is of concern in light of recent data regarding the risks of sequential instrument use when the application of forceps may follow a VE failure. In general, as mentioned above, infants from sequential instrument deliveries have worse outcomes than those delivered either by a cesarean delivery or by a vaginal procedure that was successful on the first attempt.
  • Maternal injury: Any instrumental delivery is associated with an increased risk of perineal/rectal injury versus the incidence of these complications following either a spontaneous or a cesarean delivery. A consistent finding is an increased incidence of perineal tears following forceps as opposed to VE deliveries. [63, 64, 2, 62, 66, 60, 40]
  • Fatal fetal injury: A study reported by Towner and coworkers collected mode of delivery and birth injury data from several large populations. [41] The report by Demissie and coworkers includes information from total United States births for 1995-8 (n= 11,939,388) as well as data from New Jersey (375,351). [45] These large numbers permit statistical evaluation of mortality information as most other studies have too restricted numbers due to the low incidence of fatal injury. These data indicate that delivery by VE is least as safe as forceps delivery with fatal complications in both cohorts statistically similar.

Other fetal injuries

Facial nerve (VII) palsies are more common following forceps operations (4.5 per 1,000) than VE procedures (0.46 per 1,000).[41] However, these injuries are uncommon, virtually always transitory and thus not of great clinical import.

In the Towner series, infants delivered by VE had a significantly higher rate of intracranial hemorrhage (ICH) (including subdural and other cerebral bleeds), brachial plexus injuries, convulsions, and central nervous system depression versus infants delivered spontaneously. VE neonates are also more likely to need mechanical ventilation after delivery than spontaneously delivered infants. Similar findings were noted by Wen and coworkers in a series of 305,391 deliveries.[47] A retrospective, single-hospital study by Zuarez-Easton et al found VE to be an independent risk factor for neonatal brachial plexus injury only in primiparous women. The study involved 142 newborns with brachial plexus injury and 286 controls.[76]

However, in the Towner report, which included 584,340 total deliveries, no significant differences were reported in the risk for the more severe neonatal injuries, including ICH, between infants delivered by cesarean delivery during labor (0.25 per 1,000) and infants delivered by either VE (0.15 per 1,000) or forceps (0.26 per 1,000) alone.

Table 3. Incidence of Fetal Intracranial Hemorrhage (n=584,340)[41] (Open Table in a new window)

Mode of Delivery Incidence of ICH
Cesarean delivery with no labor

Spontaneous vaginal delivery

1 per 2,750

1 per 1,900

Cesarean delivery during labor

Vacuum-assisted vaginal delivery

Forceps-assisted vaginal delivery

1 per 907*

1 per 860*

1 per 664*

Cesarean delivery after failed vacuum or forceps-assisted delivery 1 per 334
*Differences not statistically significant



These and other data implicate the events of labor and the fact of vaginal delivery, as opposed to any specific delivery instrument, as a major factor in the etiology of serious intracranial injuries. Note that in this series only cesarean delivery without labor is protective, resulting in a reduced risk for ICH.

In the Demissie study, infant deaths (0-364 days) for the United States cohort were essentially equal for infants delivered spontaneously (n=10,137,144), by forceps (n=435,339) or by VE (n=891,340) attesting in part to the safety of VE operations.[45]

Other clinical considerations

In general, when an emergency delivery is required and a vaginal operative trial is elected, greater success and less danger result when a delivery instrument is chosen based on prior operator experience and proven skill. Other important considerations include:

  • Presumed fetal jeopardy and nonreassuring monitoring: In presumed fetal jeopardy at a low station (+2/5 +/- cm), many prefer to apply forceps rather than the vacuum. However, the differences in safety or speed between these instruments are minimal. Either the vacuum extractor or the forceps is appropriate in these urgent cases, depending on the comfort level of the clinician.
  • Maternal parity: Forceps-related lacerations and extensions are less likely among multiparas.
  • Shoulder dystocia: The risk is increased with VE. This may relate to the physics of extraction, specifically the vector of force generated by the VE versus the forceps. VE may also be preferentially used as a trial instrument when fetal bulk is believed to be large and assistance in the second stage is required.
  • Heavy cranial molding and caput: When the situation is without exigency, numerous issues arise. The forces of labor normally result in some cranial molding and often caput. The combination of molding and caput succedaneum formation obscures traditional landmarks. Even experienced clinicians may have difficulty assessing fetal position and station. Careful attention to palpation of the cranial fontanels, suture lines, orbital ridges, or the fetal ear helps establish the correct cranial orientation and station. In difficult cases, real-time ultrasonographic scanning helps in evaluating fetal cranial positioning and station, particularly in occiput posterior positions. Visualization of the fetal orbits, cranial anatomy, position of the fetal spine, and other anatomic landmarks is often easy, which verifies the position. If the fetal head is heavily molded, the cranial bones overlap, and the presenting part remains high, disproportion is likely. Thus, no attempt at an instrumental delivery is appropriate,andcesarean delivery is the best management.
  • See the image below.
    Digital evaluation of cranial molding. Digital evaluation of cranial molding.
  • Prematurity (< 36 wk): The use of any instrument to assist delivery of a premature infant is controversial. Older data suggest that gentle assisted delivery of the fetal head on the perineum using a classic forceps might reduce cranial trauma. However, this traditional application has unimpressive literature support. As the inherent risks of fetal intracranial or scalp hemorrhage are greater in premature infants than in full-term infants, the vacuum extractor is relatively contraindicated for applications in infants younger than 36 weeks. Yet, as data on this issue are both limited and often anecdotal, this contraindication cannot be absolute. If an extractor is chosen for a preterm pregnancy, a soft-cup design is preferred.
  • Breech presentations: In breech presentations, VE use is contraindicated. A vaginal breech delivery is a potential indication for the application of forceps. Either Piper or Kjelland (Kielland) forceps are appropriate for the after-coming head.
  • Cesarean delivery: As previously reviewed, VE may assist in extraction. The best use is when the fetus assumes a transverse or high oblique lie after rupture of the membranes.
  • Multiple gestations: The vaginal delivery of a second cephalic-presenting twin is often a good case for a vacuum extractor. Such extractions are usually easy because of dilation of the birth canal following the delivery of the first infant. A VE operation at cesarean delivery may obviate the need for extraction of the second twin and avoid an extension of the cesarean wound. Here, any type of VE is acceptable.

Choice of instrument

Practice suggestions: The accoucheur must carefully consider the fetal condition, available resources, extent of analgesia, likelihood of maternal cooperation, and personal skill level when choosing the instrument for operative vaginal delivery. Recommendations are as follows:

  • Outlet-pelvic and low-pelvic operations (rotation < 45°): With adequate analgesia, the vacuum extractor and forceps are equivalent instruments. However, use of forceps is more likely to risk a maternal perineal injury. If a VE is chosen, any cup type is acceptable. The authors' recommendation is the use of a soft plastic cup to reduce scalp injury.
  • Rotations greater than 45° and midpelvic operations: For heads in transverse position, the appropriate cup choices include an occiput posterior (OP) metal cup or a rigid plastic or M-cup design. Forceps may also be used for these positions, but these operations are restricted to experienced physicians only. First, attempt a manual rotation because this may prove successful or partially successful either replacing the need for instrumentation or easing the subsequent procedure.
  • If an extraction is attempted from a direct OP position, appropriate choices include an OP metal cup or a rigid plastic or M-cup OP design. Forceps may also be applied to OP either for a direct "face to pubes" pull or, in experienced hands, for a rotation. Note that if the attempt is to deliver an OP infant directly, the pull can prove difficult and risks maternal soft-tissue injury. Forceps rotations from OP to OA (Scanzoni or similar procedures) are restricted to experienced accoucheurs only.
  • Instrumental deliveries that do not involve significant cranial asynclitism are equally well managed by any vacuum instrument. Note that VE is most likely to fail due to a deflexed OP presentation because of difficulty in proper placement of the vacuum cup. Also, in comparison to forceps, the vacuum extractor cannot exert the same level of traction that is possible with forceps.


Opinions for standard vacuum extraction procedures

The vacuum extractor is an effective and safe device for assisted vaginal delivery and an important addition to the modern obstetrical armamentarium. Proper education in the use of these devices is mandatory. The clinician must treat this instrument with respect to maximize the possibilities of its success while limiting the risks of maternal or fetal injury.

  • Routine notification of the pediatrician or the newborn attendants that a vacuum extraction (VE) operation has been performed is recommended to assure appropriate postoperative observation of the neonate.
  • Trauma to the maternal birth canal and perineum following instrumental delivery damages maternal pelvic nerves and fascial supports and can disrupt the anal sphincter, resulting in permanent pelvic floor injury or rectal dysfunction. The available data, although incomplete, prompts caution in instrumental deliveries to avoid episiotomy and perineal injury when possible.
  • The likelihood of serious infant injury is increased when multiple or excessive efforts at extraction are performed by either forceps or a vacuum extractor. An unsuccessful operation with any instrument should prompt great caution in applying an alternative device. Sequential instrument use is restricted to selected cases conducted only by highly experienced surgeons with the understanding that fetal risk is increased.

Routine practice

These recommendations are based on the authors' experience and on large clinical series that reported a low incidence of injury when similar rules were followed.

  • Informed consent is needed.
  • Limit the number of tractions with the VE to 4 or 5, with caution to ascertain true progress after 3.
  • Limit unintended cup detachments or pop-offs to no more than 2 or 3 with soft cups and 1 or 2 with either metal or rigid plastic cups.
  • Require advancement of the presenting part with the initial or, certainly, the second traction.
  • Restrict the overall duration of the procedure to less than 30 minutes (note that some clinicians propose 20 min). Reduce vacuum between traction efforts.
  • Avoid sequential use of the vacuum extractor and forceps.
  • Abandon any procedure that proves difficult.
  • Dictate all procedures or record in an electronic medical record in the same manner as any operation.


Traditionally, education in surgical procedures including forceps and vacuum extraction (VE) operations was based on the "see one, do one" method, in which the techniques of the surgery were taught at the perineum on actual cases. These clinical sessions were reinforced by practice on various pelvic models and review of textbook information. The most important part of the education was recognized to be the "live" segments, where the "gray-haired masters" inculcate the neophytes in the mysteries of proper technique and other pearls of wisdom resulting from years of clinical experience. This model of education certainly does not apply in many services for numerous reasons.

Highly experienced accoucheurs are progressively lost to practice by death and retirement. "Practice" procedures performed for purposes of education are no longer performed. The overall use of instrumentation has declined, and many younger practitioners were never trained in the more complex types of vaginal instrumental delivery. Thus, educating a new series of practitioners has become difficult, and many clinicians depend entirely on outlet VE procedures only as they are uncomfortable or uncertain of their abilities to attempt higher extractions or conduct a forceps delivery.

The recent introduction of various methods of simulation of obstetric procedures is an important step in the right direction that has returned a method for "near clinical" forceps and VE procedures. The continuous improvement in these techniques and the development of better simulations will go a long way toward maintaining appropriate skills in this important part of obstetric lore.

Contributor Information and Disclosures

John P O'Grady, MD, MA Professor of Obstetrics and Gynecology, Tufts University School of Medicine; Medical Director, Family Life Center and Mercy Perinatal Service, Mercy Medical Center; Attending Physician, Department of Obstetrics and Gynecology, Baystate Medical Center and St Elizabeth's Medical Center

John P O'Grady, MD, MA is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine, Massachusetts Medical Society

Disclosure: Nothing to disclose.


Carolyn St Andre Research Assistant to John P O'Grady, MD, Perinatal Services, Family Life Center, Mercy Medical Center

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Richard S Legro, MD Professor, Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology, Pennsylvania State University College of Medicine; Consulting Staff, Milton S Hershey Medical Center

Richard S Legro, MD is a member of the following medical societies: American College of Obstetricians and Gynecologists, Society of Reproductive Surgeons, American Society for Reproductive Medicine, Endocrine Society, Phi Beta Kappa

Disclosure: Received honoraria from Korea National Institute of Health and National Institute of Health (Bethesda, MD) for speaking and teaching; Received honoraria from Greater Toronto Area Reproductive Medicine Society (Toronto, ON, CA) for speaking and teaching; Received honoraria from American College of Obstetrics and Gynecologists (Washington, DC) for speaking and teaching; Received honoraria from National Institute of Child Health and Human Development Pediatric and Adolescent Gynecology Research Thi.

Chief Editor

Thomas Chih Cheng Peng, MD Professor (Collateral), Department Obstetrics and Gynecology, Virginia Commonwealth University School of Medicine, VCU Health System

Thomas Chih Cheng Peng, MD is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine, Society for Maternal-Fetal Medicine

Disclosure: Nothing to disclose.

Additional Contributors

Suzanne R Trupin, MD, FACOG Clinical Professor, Department of Obstetrics and Gynecology, University of Illinois College of Medicine at Urbana-Champaign; CEO and Owner, Women's Health Practice; CEO and Owner, Hada Cosmetic Medicine and Midwest Surgical Center

Suzanne R Trupin, MD, FACOG is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine, International Society for Clinical Densitometry, AAGL, North American Menopause Society, American Medical Association, Association of Reproductive Health Professionals

Disclosure: Nothing to disclose.


The editorial and research assistance of Carolyn Taugher in the preparation of the current paper is gratefully acknowledged.

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Ghosting or phantom application of vacuum extraction.
Cranial flexion or pivot point.
Incorrect sites for cup placement.
Changing vector of traction.
Lateral view of maternal pelvis. Pelvic axis/curve is demonstrated.
Scalp cross-section and hemorrhage sites.
Digital evaluation of cranial molding.
Chignon sign.
Table 1. Proposed Classification for Vacuum Extraction Procedures According to Fetal Station and Cranial Position (modified from ACOG Practice Bulletin # 17, June, 2000)
Type of Procedure Description of Classification *
Outlet-vacuum operation The fetal head is at or on the perineum; the scalp is visible at the introitus without separating the labia; the fetal skull has reached the pelvic floor. The sagittal suture is in the AP diameter (ROA, LOA, OA) or posterior (ROP, LOP, OP) position.
Low-vacuum operation The position/station of the fetal head does not fulfill the criterion for an outlet operation; the leading edge of the fetal skull is at station +2/5 cm, but has not reached the pelvic floor.†
Subdivisions (a) Position is occiput anterior (OA, LOA, ROA).

(b) Position is occiput posterior (OP, LOP, ROP) or transverse (LOT, ROT).

Midvacuum operation Station
Subdivisions (a) Position is occiput anterior (OA, LOA, ROA).

(b) Position is occiput posterior (OP, LOP, ROP) or transverse (LOT, ROT).

Vacuum-assisted cesarean delivery This includes all vacuum-assisted cesarean deliveries, unspecified technique.
Special vacuum operations This includes vacuum extraction operations not otherwise specified; full details are described in the dictated operative note.
High-vacuum operation Such procedures are not included in the classification.
OA: occipitoanterior; ROA: right occipitoanterior; LOA: left occipitoanterior; OP: occipitoposterior; LOP: left occipitoposterior; ROP: right occipitoposterior; LOT: left occipitotransverse; ROT: right occipitotransverse

*The type of operation coded in the medical record is determined by pelvic examination noting the position and station of the fetal head at the time the extraction is initiated.

†To standardize nomenclature, especially as other methods were used in the past, the authors recommend the ACOG ±5 cm system for the reporting of station, with certain modifications. Station (recorded as +5 to –5 cm) is defined as the distance in centimeters from the leading bony portion of the fetal skull to the imaginary plane of the maternal ischial spines. In the authors’ practice, they determine station by first conducting a pelvic examination, noting the distance from the presenting part to the ischial spines. This number is then entered into the medical record, followed by a notation specifying the technique used for reporting. Thus, if the clinician's estimate is that the bony presenting part is 2 cm below the plane of the ischial spines, a station of +2/5 cm is recorded.

Table 2. Number of Tractions Required in Vacuum Extraction and Forceps Deliveries*
Number of Traction Efforts Successful Malmström Vacuum Extractor Deliveries (n=433) Successful Forceps Deliveries† (n=555)
1-2 296 (68.4%) 213 (38.4%)


108 (24.9%) 270 (48.6%)
≥5 29 (6.7%) 72 (12.9%)
* Breech, cesarean delivery, and transverse lies, are excluded.[38]

Type unspecified

Table 3. Incidence of Fetal Intracranial Hemorrhage (n=584,340) [41]
Mode of Delivery Incidence of ICH
Cesarean delivery with no labor

Spontaneous vaginal delivery

1 per 2,750

1 per 1,900

Cesarean delivery during labor

Vacuum-assisted vaginal delivery

Forceps-assisted vaginal delivery

1 per 907*

1 per 860*

1 per 664*

Cesarean delivery after failed vacuum or forceps-assisted delivery 1 per 334
*Differences not statistically significant
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