Title:
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Risk of recurrent stillbirth : an Individual Participant Data (IPD) meta-analysis
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Background: Previous meta-analyses assessing risk of recurrent stillbirth were limited by clinical and statistical heterogeneity. This study aimed to address these limitations using individual participant data (IPD). Methods: An online survey of perinatal databases in high-income countries identified potential datasets for inclusion in the IPD meta-analysis. IPD from Scotland, Finland and Malta were analysed to calculate risk of stillbirth in a second or subsequent pregnancy using logistic regression and survival analysis. The chance of having another stillbirth if previous stillbirth was explained or unexplained was also investigated. Results: The pooled dataset included 1,068,258 women, 3,529 with a stillbirth and 1,064,729 with a livebirth in a second pregnancy. Women with a stillbirth in a second pregnancy had increased odds of stillbirth in a previous pregnancy, adjusted OR 3.41, 95% CI (2.72 TO 4.28). Increasing maternal age, overweight and obesity, having no partner, lower social class, smoking during pregnancy and short (1 year or less) and long (≥6 years) interpregnancy intervals were independent risk factors for stillbirth in a second pregnancy as were placental abruption, diabetes, threatened miscarriage, intra-uterine growth restriction and cord or hand prolapse. Compared to women who had a livebirth in a first pregnancy, women who had a stillbirth were more likely to have a subsequent stillbirth, adjusted HR 2.25, 95% CI (1.86 to 2.72). Women who were younger than 20, smoked, deprived, had no partner, had diabetes mellitus, preeclampsia, placental abruption or growth restricted foetus in their first pregnancy were also more likely to have a subsequent stillbirth. There was no difference in the risk of subsequent stillbirth whether the previous stillbirth was explained or unexplained (OR .0.92, 95% CI 0.64 to 1.32). Conclusion: Women with a stillbirth in a first pregnancy have a higher risk of recurrence in a subsequent pregnancy even when the cause is unknown.
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