Research adds insight on stillbirth risk factors

Common wisdom informed by retrospective cohort studies has long told us that inducing labor prior to 41 weeks’ gestation is associated with a higher risk of cesarean delivery in nulliparous women. However, recent observational data have suggested that women whose labor is induced actually have fewer cesarean deliveries and better perinatal outcomes, including a lower risk of stillbirth (AJOG 2012;207:502.e1-8).

In addition, a meta-analysis published in 2014, as the ARRIVE trial was taking shape, reported a 12% reduction in cesarean delivery, and a reduced risk of stillbirth, among women whose labor was induced. The initial cervical score did not impact the main findings (CMAJ. 2014 Jun 10;186[9]:665-73). If these findings are confirmed in the ARRIVE trial, we could see a new opportunity for stillbirth prevention.

Another ongoing study of 10,000 singleton pregnancies – the Nulliparous Pregnancy Outcomes: Monitoring Mothers-to-Be (nuMoM2b) study – may also lead to prevention strategies in women for whom the current pregnancy will lead to their first delivery. Among the questions being examined in this eight-site study are whether sleep-disordered breathing, or apnea, and a supine sleep position are risk factors for adverse pregnancy outcomes including stillbirth.

Supine sleeping in the last month of pregnancy was strongly associated with stillbirth in a recent analysis from the Sydney Stillbirth Study (Obstet Gynecol. 2015 Feb;125[2]:347-55), and an early analysis of a nuMoM2b subset has shown associations between sleep-disordered breathing in midpregnancy and the development of hypertensive disorders of pregnancy, and between sleep-disordered breathing in early- and mid-pregnancy and gestational diabetes (Am J Obstet Gynecol. 2015;212:S424-425).

The possible role of low-dose aspirin in preventing stillbirth also needs more exploration. A recent randomized trial of women attempting to become pregnant after having had one or two prior pregnancy losses found no difference overall in live birth rates between those who took low-dose aspirin and those assigned to placebo. However, there was one subgroup – women with a single loss at less than 20 weeks’ gestation during the previous year – in which live birth rates were higher in the aspirin group (Lancet. 2014 Jul 5;384[9937]:29-36). More research is necessary to determine if low-dose aspirin administration in women with a previous stillbirth improves pregnancy outcome.

Dr. Reddy is a member at the Pregnancy and Perinatology Branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. She is a board-certified ob.gyn. and maternal-fetal medicine specialist. She is the program scientist for the Maternal-Fetal Medicine Units Network and for the Stillbirth Collaborative Research Network. The comments and views of the author do not necessarily represent the views of the NICHD.