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 livebirth 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 if first pregnancy outcome had an effect on time to, or the number of pregnancies preceding subsequent stillbirth.Results The pooled dataset 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 to women with a live birth, women with an initial stillbirth were more likely to have a subsequent stillbirth, adjusted hazard ratio (HR) 2.25, 95% CI (1.86 to 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 <25 or ≥40 years, smoking, low socioeconomic status, being single, pre-existing diabetes, preeclampsia, placental abruption or delivery of a growth restricted baby 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 one year. The absolute risk of stillbirth in a subsequent pregnancy for women with stillbirth and livebirth in a first pregnancy were 2.5% and 0.5% respectively.Conclusion Compared to 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.
Bibliographical noteFinancial Disclosure
Kathleen Lamont was awarded an Elphinstone scholarship from the university of
Aberdeen, Scotland. In addition, money from a NHS Grampian endowment fund financed storage of data. Sohinee Bhattacharya reports that money was paid to their institution from the NHS Grampian Endowment fund, Medical Research Scotland, and the Wellcome Trust ISSF fund. Sohinee Bhattacharya’s husband has co-authored previous publications based on a similar dataset. He is the Head of School of medicine, medical Sciences and Nutrition at the University of Aberdeen where she is also employed. The other authors did not report any potential conflicts of interest.