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.

Risk of recurrent stillbirth: systematic review and meta-analysis.

OBJECTIVE: To determine the risk of recurrent stillbirth. DESIGN: Systematic review and meta-analysis of cohort and case-control studies. DATA SOURCES: Embase, Medline, Cochrane Library, PubMed, CINAHL, and Scopus searched systematically with no restrictions on date, publication, or language to identify relevant studies. Supplementary efforts included searching relevant internet resources as well as hand searching the reference lists of included studies. Where published information was unclear or inadequate, corresponding authors were contacted for more information. STUDY SELECTION: Cohort and case-control studies from high income countries were potentially eligible if they investigated the association between stillbirth in an initial pregnancy and risk of stillbirth in a subsequent pregnancy. Stillbirth was defined as fetal death occurring at more than 20 weeks' gestation or a birth weight of at least 400 g. Two reviewers independently screened titles to identify eligible studies based on inclusion and exclusion criteria agreed a priori, extracted data, and assessed the methodological quality using scoring criteria from the critical appraisal skills programme. Random effects meta-analyses were used to combine the results of the included studies. Subgroup analysis was performed on studies that examined unexplained stillbirth. RESULTS: 13 cohort studies and three case-control studies met the inclusion criteria and were included in the meta-analysis. Data were available on 3,412,079 women with pregnancies beyond 20 weeks duration, of who 3,387,538 (99.3%) had had a previous live birth and 24,541 (0.7%) a stillbirth. A total of 14,283 stillbirths occurred in subsequent pregnancies, 606/24,541 (2.5%) in women with a history of stillbirth and 13,677/3,387,538 (0.4%) among women with no such history (pooled odds ratio 4.83, 95% confidence interval 3.77 to 6.18). 12 studies specifically assessed the risk of stillbirth in second pregnancies. Compared with women who had a live birth in their first pregnancy, those who experienced a stillbirth were almost five times more likely to experience a stillbirth in their second pregnancy (odds ratio 4.77, 95% confidence interval 3.70 to 6.15). The pooled odds ratio using the adjusted effect measures from the primary studies was 3.38 (95% confidence interval 2.61 to 4.38). Four studies examined the risk of recurrent unexplained stillbirth. Methodological differences between these studies precluded pooling the results. CONCLUSIONS: The risk of stillbirth in subsequent pregnancies is higher in women who experience a stillbirth in their first pregnancy. This increased risk remained after adjusted analysis. Evidence surrounding the recurrence risk of unexplained stillbirth remains controversial.