Lamont et al conducted a large cohort study to investigate how factors including the outcome of a first pregnancy (stillbirth or live birth), affect the risk of having a stillbirth in any subsequent pregnancy. They hypothesized that compared with women who had a previous live birth, women whose first pregnancy resulted in a stillbirth had an increased risk of stillbirth in any subsequent pregnancy.
Authors conducted a cohort study using perinatal data from Finland, Malta, and Scotland. Women who had at least two singleton deliveries were included. The exposed and unexposed cohorts comprised women with a stillbirth and live birth in their first pregnancy, respectively. The risk of stillbirth in any subsequent pregnancy was assessed using a Cox proportional hazards model. Time-to-event analyses were conducted to investigate whether first pregnancy outcome had an effect on time to or the number of pregnancies preceding subsequent stillbirth.
The pooled data set included 1,064,564 women, 6,288 (0.59%) with a stillbirth and 1,058,276 with a live birth in a first pregnancy.
Compared with women with a live birth, women with a stillbirth in the first pregnancy were more likely to have a subsequent stillbirth (adjusted hazard ratio [aHR] 2.25, 95% CI 1.86–2.72).
For women with more than two pregnancies, the difference in risk of subsequent stillbirth between the two groups increased with the number of subsequent pregnancies.
Maternal age younger than 25 years or 40 years and older, smoking, low socioeconomic status, not having a partner, pre-existing diabetes, preeclampsia, placental abruption, or delivery of a growth-restricted neonate in a first pregnancy were independently associated with subsequent stillbirth.
Compared with women with a live birth in the first pregnancy, women with a stillbirth were more likely to have another pregnancy within 1 year. The absolute risk of stillbirth in a subsequent pregnancy for women with stillbirth and live birth in a first pregnancy were 2.5% and 0.5%, respectively.
Women whose first pregnancy resulted in the delivery of a growth-restricted or preterm neonate were also at increased risk of having a subsequent stillbirth, the risk increasing with decreasing gestational age at first delivery.
In conclusion, women with a stillbirth in their first pregnancy have more than double the risk of stillbirth in any subsequent pregnancy. Despite significantly raised relative risk, the absolute risk remains low. Better screening for placental dysfunction may help identify women at higher risk of stillbirth. Findings from this study also highlight the importance of counseling women regarding modifiable risk factors to improve pregnancy outcomes after a stillbirth.
Source: Lamont et al; Recurrent Stillbirth; (Obstet Gynecol 2022;139:31–40), American College of Obstetricians and Gynecologists
DOI: 10.1097/AOG.0000000000004626