Risk of Recurrent Stillbirth in Subsequent Pregnancies

OBJECTIVE: To compare the prospective risk of stillbirth between women with and without a stillbirth in their first pregnancy. METHODS: We 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. RESULTS: 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. CONCLUSION: Compared with women with a live birth in a first pregnancy, women with a stillbirth have a higher risk of subsequent stillbirth irrespective of the number and sequence of the pregnancies. Despite high relative risk, the absolute risk of recurrence was low.