Always anticipate massive hemorrhage and preterm delivery in a woman with placenta previa. Document adequate preparation, including transfer to a higher level of care, if necessary.
Hemostasis may be established by one or more of the following:
Oversewing the placental implantation site
Bilateral uterine artery ligation (O'Leary stitch)
Internal iliac artery ligation
Circular interrupted ligation around the lower uterine segment both above and below the transverse incision
Packing with gauze or tamponade with the Bakri balloon catheter
Diffuse bleeding often occurs at the implantation site within the lower uterine segment after delivery.  As such, knowledge in the management of acute and heavy blood loss is imperative. Activation of the massive transfusion protocol may be warranted depending on the situation. The use of uterotonics, including methylergonovine maleate (Methergine), 15 methyl prostaglandin F2 alpha (Hemabate), concentrated oxytocin, or misoprostol are excellent pharmacological agents to help resolve uterine atony, the main cause of hemorrhage post-delivery.
Other options include surgical management, as listed above. Often a combination of medical and surgical interventions are utilized.
In instances where significant bleeding ensues, rapid replacement of blood products is a priority. In such instances, activation of the Massive Transfusion Protocol is warranted, allowing for stabilization of a patients hemodynamic status by way of rapid supply and infusion of blood products.
Management of Vaginal Bleeding
Stepwise approach to managing 3rd trimester vaginal bleeding
Patient should be assessed in the labor and delivery unit and the focus should be on maternal hemodynamic stability and fetal well-being. Evaluation should be initiated through close observation of maternal vital signs and initiation of electronic fetal monitoring. Intravenous access is imperative and should be initiated the moment the patient is brought to the labor floor. CBC and T&S should be sent to determine Hg level and possible need for administration of Rh immunoglobulin pending maternal Rh status. If significant vaginal bleeding is noted during evaluation, blood should be cross matched in preparation for rapid replacement of blood volume. Two to four units of blood may be required rather quickly, if hemorrhage ensues. Initiation of massive transfusion protocol may be appropriate if rapid access to blood products is necessary. 
Once the patient is deemed stable and fetal well-being has been noted, etiology of the vaginal bleeding can be assessed. Assessment of the placenta should be undertaken through ultrasound by either a transabdominal or transperineal approach. Sterile speculum exam should follow to further assess the quantity and source of the bleeding. It is imperative that a digital cervical exam is never performed in a patient with concern or ultrasound confirmed placenta previa as this may lead to torrential hemorrhage due to disruption of the placenta and its vessels. 
Expectant management with close observation is indicated in situations where the fetal gestational age is less than 36weeks of gestation as long as reassuring fetal monitoring is present and vaginal bleeding has resolved or significantly decreased. Administration of betamethasone should be provided if gestational age is less than 34weeks. If bleeding is severe or non-reassuring fetal monitoring is present then emergency cesarean delivery is indicated. 
Indications for hospitalization
For an otherwise uncomplicated pregnancy, continue expectant management in a woman with placenta previa until an episode of bleeding occurs. Studies have not shown any difference regarding maternal or fetal morbidity with home management versus hospitalization prior to the first bleed in these women. Any patient with suspected or known placenta previa and new onset vaginal bleeding should be admitted to the hospital for close monitoring. It is challenging to standardize the duration of a patients hospitalization given the episodic nature of the bleeding. Patients should be closely monitored for a minimum of 48hours during a sentinel bleeding episode.  With certain patients, after the initial episode of bleeding has resolved and fetal evaluation has noted to be reassuring, it is appropriate to undergo expectant mgmt. at home.  Several studies have shown this to be a safe approach as long as certain criteria are met.  However, it is advisable to continue hospitalization in any patient with multiple episodes of bleeding or with those pts with limited access to appropriate medical care if they were to be discharged.  At times this may result in hospitalization until delivery.
If bleeding persists and is heavy, preparation for immediate surgery is indicated. In cases where placental location remains uncertain, a double setup examination—in which one management team is prepared for an uneventful vaginal delivery, and a second team is prepared for an immediate cesarean delivery, as needed—may be considered.
Order clotting studies (ie, prothrombin time/activated partial thromboplastin time [PT/aPTT], fibrinogen) if concern arises for disseminated intravascular coagulation (DIC).
Tocolytics may be considered in cases of minimal bleeding and extreme prematurity in order to administer antenatal corticosteroids. One study appeared to suggest that the use of tocolytics increases the duration of pregnancy and increases the baby's birth weight without causing adverse effects on the mother and the fetus.  However, a review article by Bose et al concluded that there is no improvement in perinatal outcome with prolonged tocolytics, and tocolysis beyond 48 hours is not clinically indicated. 
If more than one episode of bleeding occurs during gestation (at viability or >24 wk), the clinician should consider hospitalization until delivery, given the increased potential for placental abruption and fetal demise.
Mode of delivery
In general, mode of delivery is directed by the proximity of the leading edge of the placenta in relation to the internal os of the cervix. Several professional organizations and previous studies have recommended elective cesarean delivery when the placenta is les than 2 cm from the internal os. In a retrospective study of 121 pregnancies complicated by placenta previa, 90% of pregnancies with placental edge-to-cervical os distance of 1-2 cm resulted in cesarean deliveries.
Another consideration is the distance to the internal cervical os and the mode of delivery. In general, women with a placental edge–to–cervical os distance that is greater than 2 cm from the internal cervical os can be offered a trial of labor.  However, a more recent study by Vergani et al reported that more than two thirds of women with placenta previa who have a placental edge–to–cervical os distance greater than 1 cm deliver vaginally without an increased risk of hemorrhage.  The decision to proceed with a trial of labor should be made on an individualized basis at a center that provides 24-hour anesthesia, in-house obstetricians, and trauma blood transfusion protocols.
There is limited data to guide management and as such optimal timing of delivery is controversial. However, in patients with uncomplicated placenta previa, delivery is recommended in the late preterm period between 36weeks 0days to 37weeks 0days of gestation.  This provides for the lowest possible risk of bleeding due to labor while also decreasing the risks of prematurity for the fetus.
Earlier delivery may be warranted, however, based on bleeding profile, previous bleeding history, or preterm labor.  Each patient and their situation must be taken into individual account.
As noted earlier, the distance between the placental edge and internal cervical os on transvaginal ultrasonography after 35 weeks’ gestation is valuable in planning route of delivery. In general, there is a higher cesarean rate associated with placental edge–to–cervical os distances of less than 2 cm.
In performing cesarean delivery for placenta previa, a low transverse uterine incision is most often used. However, a vertical uterine incision may be considered secondary to an anterior placenta and risk of fetal bleeding.
If the patient is at increased risk for invasive placentation (accreta, increta, or percreta), then the patient and surgical team must be prepared prior to delivery. These invasive placentations carry a high mortality rate (7% with placenta accreta) as well as a high morbidity rate (blood transfusion, infection, adjacent organ damage).
Traditionally, uterine atony was the most common cause of cesarean hysterectomy; however, a meta-analysis by Machado showed that abnormal placentation is the most common cause, occurring in up to 45% of cesarean hysterectomies.  Risk for cesarean hysterectomy is increased by the presence of complete placenta previa and a history of cesarean delivery or prior abortion. 
Controlling blood loss
These complicated pregnancies must have delivery plans that include patient-matched blood and informed consent for possible cesarean hysterectomy. Predelivery placement of balloon catheters for angiographic embolization of pelvic vessels is a technique described in reducing blood loss associated with cesarean hysterectomy and provides the opportunity to manage potential postoperative bleeding with embolization rather than operative re-exploration. 
Aortic balloon occlusion prior to cesarean hysterectomy has also been demonstrated to reduce blood loss.  Other means to control hemorrhage include the following:
B-Lynch or parallel vertical compression sutures
Uterine artery ligation (O'Leary stitch)
Hypogastric artery ligation
In the case of a small and focal placenta accreta, resection of the implantation site and primary repair may allow for uterine preservation.
Women with placental previa are considered to have high-risk pregnancies, and a multidisciplinary team is involved in their management, including specialists in the following areas:
Surgical oncology or general surgery, if extensive surgical dissection is anticipated
Urology, if significant involvement of the bladder is anticipated
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