Effect of Adjunctive Misoprostol on Blood Loss at Vaginal Delivery

Some maternal blood loss normally occurs at the time of vaginal delivery. The best estimates indicate that a loss of approximately 500 mL is average, with a range of about 250-700 mL.[1,2] Some of this bleeding arises from birth canal lacerations or surgical incisions (i.e., episiotomy), but most derives from the vessels exposed in the uterine wall at the placental site once the placenta has separated.

Under normal circumstances, shortly after placental separation intense myometrial contractions occur. These raise the pressure within the myometrial wall above that of the blood pressure in the vessels that traverse it, vessels that opened into the intervillous space. Flow in these vessels is thus mechanically attenuated by myometrial contraction, allowing for the formation of intravascular thrombi.

This mechanism for controlling postpartum uterine blood loss works well most of the time. If, however, the uterus remains hypotonic or atonic after delivery, excessive blood loss can occur. In the worst cases, severe uterine hemorrhage ensues. Postpartum hemorrhage is, in fact, the leading cause of maternal mortality in the world, accounting for at least 100,000 deaths annually.[3] Even in the absence of frank hemorrhage, postpartum blood loss can result in maternal anemia. Recuperation of iron stores to recover from this blood loss takes time, and may not occur, especially in low socioeconomic areas where dietary iron consumption is often deficient, and pregnancies tend to occur in close succession.

Postpartum anemia is a significant contributor to short- and long-term morbidity.[5-7] It increases the risk of infection and poor wound healing. Also, the associated fatigue may interfere with the mother's ability to administer child care and to bond appropriately with her infant. Anemic mothers tend to have more difficulty with nursing, and may produce iron-deficient milk. There is thus a strong rationale to minimize postpartum blood loss.

In most US hospitals, parturients receive a high dose of intravenous or intramuscular oxytocin immediately after delivery. This approach has been shown in several studies to reduce the risk of postpartum hemorrhage, [8-11] and is practiced routinely at Queens Hospital Center. Investigators will employ an intravenous infusion of oxytocin (Pitocin®) at a rate of about 50-100 mU/minute. Despite this approach, there is still substantial blood loss at delivery, based on the investigator's preliminary observations shown below. This provides the rationale to determine whether use of an adjunctive drug, namely misoprostol 600 µg rectally, administered after delivery, might reduce blood loss further than does oxytocin alone, thus decreasing the risk of morbidity related to postpartum anemia.