Aggressive blood replacement also is required to reverse the coagulopathy associated with AFE. Transfusion of packed red blood cells is a priority, but fresh frozen plasma, platelets, and cryoprecipitate also should be available for prompt administration.
There have been promising reports of the use of recombinant factor VIIa (rVIIa) for treating hemorrhage in patients with AFE in recent years, but a recent review of case reports of AFE from 2003 to 2009 suggests that the procoagulant may actually worsen outcomes (Anesthesiology 2011;115:1201-8). Indeed, unlike patients with other types of postpartum hemorrhaging, women with AFE have high circulating tissue factor concentrations. Recombinant factor VIIa can combine with tissue factor and form intravascular clots, resulting in thrombosis of major organs.
If the patient is undelivered and has cardiac arrest, an emergency cesarean section is indicated. Prompt delivery during the resuscitation process not only increases the chances of perinatal survival without neurological sequelae, but also improves the maternal resuscitation effort. We have a 4-minute window for delivery from the time the code is called to avoid neurologic injury to the fetus and optimize outcomes for the mother. This 4-minute principle was adopted by the American Heart Association in 1986, and its clinical use has been supported by 20 years of published case reports since then (Am. J. Obstet. Gynecol. 2005;192:1916-21).
Although outcomes with AFE may be improving somewhat, AFE still causes significant morbidity and mortality. Investigators in the Australian AFE cohort study, for instance, recently reported maternal and perinatal fatality rates of 35% and 32%, respectively. These rates were similar to those from the U.K. Obstetric Surveillance System, according to the authors (BJOG 2010;117:1417-21).
Ruptured Uterus
In an effort to reduce rates of cesarean deliveries, obstetricians are swinging back once again to encouraging more women to attempt vaginal birth after cesarean delivery (VBAC). Because the rates of uterine rupture are higher in women who attempt VBAC, our index of suspicion should be acute for any woman who is laboring after having had a prior cesarean delivery. We also must do everything we can to assess a patient’s risks of failed VBAC resulting in emergency cesarean section and uterine rupture.
The American College of Obstetricians and Gynecologists (ACOG) now recommends that most women with one previous cesarean delivery and with a low transverse incision be counseled about VBAC and offered a trial of labor. ACOG points out in its 2010 practice bulletin on VBAC that in several large studies, the uterine rupture rate after a trial of labor in such women was approximately 0.5-0.9%.
The College also says that many women previously considered to be at high risk may now be considered candidates for a trial of labor after cesarean section (TOLAC). Among the conditions that are no longer necessarily contraindications for attempted VBAC: two previous low transverse cesarean deliveries; suspected fetal macrosomia; twin gestations; more than one previous cesarean delivery; a previous low vertical incision; gestation beyond 40 weeks; and even external cephalic version for breech presentation (Obstet. Gynecol. 2010;116:450-63).
The ACOG bulletin addresses the importance of counseling, and mentions the possible utility of a nomogram developed for predicting the chance of successful VBAC for individual patients. The tool incorporates six variables that are ascertainable at the first prenatal visit, including maternal age, body mass index, and history of vaginal delivery (Obstet. Gynecol. 2007;109:806-12). The tool, a calculator of sorts, was developed through research by the National Institute of Child Health and Development’s (NICHD’s) Maternal-Fetal Medicine Units Network, and is also available at http://www.bsc.gwu.edu/mfmu/vagbirth.html.
Such individualized risk assessment is critical. Another model for assessing risk and informing discussions with individual patients is one developed in the United Kingdom by Dr. Gordon C. S. Smith at Cambridge University and his associates (PLoS Med. 2005:2:e252). These investigators documented that women with a predicted cesarean section risk (an unsuccessful trial of labor) of less than 20% using their model had a minimal incidence of uterine rupture of 2.0 per 1,000, while those deemed to have a high risk of cesarean delivery – defined as greater than 40% – had an incidence of uterine rupture of 9.1 per 1,000.
However small it is in absolute terms, there is an inherent risk of the uterine incision rupturing during an attempt at labor after a previous cesarean section. Indicative of this inherent risk are recommendations by the authors of numerous studies, as well as ACOG, for VBAC to be attempted in facilities with staff available for emergency care. When the fetus is actually extruded through the incision and into the abdominal cavity, there is significant risk of severe maternal and perinatal morbidity and mortality secondary to blood loss and hypoxia.