Abnormal Labor Clinical Presentation

Updated: May 08, 2017
  • Author: Nina S Olsen, MD; Chief Editor: Ronald M Ramus, MD  more...
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Presentation

History

Evaluate every pregnant patient who presents with contractions in the labor and delivery unit. Any patient in labor is at risk for abnormal labor regardless of the number of previous pregnancies or the seemingly adequate dimensions of the pelvis. Plot the progress of any patient in labor, and evaluate it on a labor curve (see images below).

Labor curve for nulliparas. Labor curve for nulliparas.
Labor curve for nulliparas versus multiparas. Labor curve for nulliparas versus multiparas.
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Physical

Upon admission to the labor and delivery unit, determine and document clinical findings.

Clinical pelvimetry, which is best performed at the first prenatal care visit, is important in order to assess the pelvic type (eg, android, gynecoid, platypelloid, anthropoid). Evaluate the position of the fetal head in early labor because caput and moulding complicate correct assessment as labor progresses. Establish and document an estimated fetal weight. Monitor fetal heart rate and uterine contraction patterns to assess fetal well-being and adequacy of labor. Perform a cervical examination to determine whether the patient is in the latent or active phase of labor.

Addressing these issues allows for an assessment of the current phase of labor and anticipation of whether abnormal labor from any of the 3 P' s may be encountered.

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Causes

Prolonged latent phase

The latent phase of labor is defined as the period of time starting with the onset of regular uterine contractions and ending with the onset of the active phase (usually 3-4 cm cervical dilation).

A prolonged latent phase is defined as exceeding 20 hours in patients who are nulliparas or 14 hours in patients who are multiparas.

The most common reason for prolonged latent phase is entering labor without substantial cervical effacement.

Power

Power is defined as uterine contractility multiplied by the frequency of contractions.

Montevideo units (MVUs) refer to the strength of contractions in millimeters of mercury multiplied by the frequency per 10 minutes as measured by intrauterine pressure transducer.

The uterine contraction pattern should repeat every 2-3 minutes.

The uterine contractile force produced must exceed 200 MVUs/10 min for active labor to be considered adequate. For example, 3 contractions in 10 minutes that each reach a peak of 60 mm Hg are 60 X 3 = 180 MVUs.

An arrest disorder of labor cannot be diagnosed until the patient is in the active phase and the contraction pattern exceeds 200 MVUs for 2 or more hours with no cervical change. Extending the minimum period of oxytocin augmentation for active-phase arrest from 2 up to 4 hours may be considered as long as fetal reassurance is noted with fetal heart rate monitoring.

Pelvis or the size of the passageway inhibiting delivery

The shape of the bony pelvis (eg, anthropoid or platypelloid) can result in abnormal labor.

A patient who is extremely short or obese, or who has had prior severe trauma to the bony pelvis, may also be at increased risk of abnormal labor.

Size and/or presentation of the infant

Abnormal labor could also be secondary to the passenger, the size of the infant, and/or the presentation of the infant. In addition to problems caused by the differential in size between the fetal head and the maternal bony pelvis, the fetal presentation may include asynclitism or head extension. Asynclitism is malposition of the fetal head within the pelvis, which compromises the narrowest diameter through the pelvis. Fetal macrosomia and other anomalies (including hydrocephalus, encephalocele, fetal goiter, cystic hygroma, hydrops, or any other abnormality that increases the size of the infant) are likely to cause deviation from the normal labor curve.

Other factors

Other factors include either a low-dose epidural or combined spinal-epidural anesthetics that minimize motor block and may contribute to a prolonged second stage. These have also been associated with an increase in oxytocin use and operative vaginal delivery. However, use of epidural for analgesia during labor does not result in a statistically significant increase in cesarean delivery. [15] Intravenous oversedation has also been implicated as prolonging labor in both the latent and active phases.

 

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