NEW ORLEANS – The safest time to deliver a woman with prior cesarean sections may be up to 2 weeks earlier than the current recommendation.
Guidelines from a number of national groups, including the Society for Maternal-Fetal Medicine, recommend planning a cesarean delivery at 39 weeks for these women. But a retrospective study has determined that maternal risk increases sharply after 37 weeks for women who have had three or more cesarean deliveries – a full 2 weeks before there is any increase in fetal risk.
"The data clearly show that the optimal time for delivery in women with three or more prior cesareans is 37 weeks," Dr. Laura Hart said at the annual Pregnancy Meeting sponsored by the Society for Maternal-Fetal Medicine.
Dr. Hart of the University of Texas Health Science Center, Houston, extracted her data from the Maternal-Fetal Medicine Units (MFMU) Cesarean Section Registry. It contains prospective data on more than 24,000 deliveries performed after prior cesarean. She examined information on 6,435 deliveries that followed at least two prior cesareans (80% after two sections and 20% after three or more).
Dr. Laura Hart
Dr. Hart analyzed both maternal and fetal outcomes. Each was a single composite comprising several endpoints. The maternal composite took into account transfusion, hysterectomy, operative injury, thromboembolic event, pulmonary edema, and death. The perinatal composite included respiratory distress syndrome, necrotizing enterocolitis (grade 2 or 3), intraventricular hemorrhage (grade 3 or 4), hypoxic ischemic injury, seizure, and stillbirth or neonatal death.
The results were expressed as a risk of the composite event relative to the number of ongoing pregnancies.
Less than half of the women who had two prior cesareans delivered at 39 weeks (46%); 11% delivered at 37 weeks, 31% at 38 weeks, and 13% at 40 weeks or more.
For these women, the risk of maternal complications was less than 5 per 1,000 ongoing pregnancies at 37 weeks. It remained low at 38 weeks (about 7/1,000). But between 38 and 39 weeks, it rose sharply, to 16/1,000. The risk remained similarly elevated at 40 weeks and beyond.
The perinatal outcomes risk was low at 37 weeks (7/1,000) and remained low at 38 and 39 weeks (7 and 9/1,000, respectively). The risk also increased sharply between 38 and 39 weeks, rising to about 20/1,000. The maternal and perinatal risk curves intersected between weeks 37 and 38, indicating that 38 weeks was probably the optimal time for delivery.
Less than half of women who had at least three prior cesareans also made it to 39 weeks (41%). About a third (35%) delivered at 38 weeks, 15% at 37 weeks, and 9% at 40 weeks or more.
Again, maternal risk was very low at 37 weeks (about 4/1,000 ongoing pregnancies). But in contrast to the risk for women with two prior deliveries, the risk for these women increased sharply and linearly over the final weeks of gestation. By 38 weeks, it had jumped to about 16/1,000. By 39 weeks, it was close to 50/1,000, and by 40 weeks and beyond, more than 50/1,000.
Conversely, perinatal risk remained fairly low in weeks 37, 38, and 39 (9, 7, and 10/1,000, respectively). Risk accelerated between weeks 39 and 40; by week 40 and beyond, it hovered just above 25/1,000. The risk curves intersected between weeks 37 and 38, indicating that 37 weeks is the optimal time for delivery.
Dr. Hart added that maternal transfusion was the main risk driver for women, followed closely by operative injury and hysterectomy.
These data were published in a supplement to the American Journal of Obstetrics and Gynecology (Amer. J. Obstet. Gynecol. 2014;210(suppl.):S27).
Dr. Hart had no financial disclosures.