Risk of stillbirth and adverse pregnancy outcomes in a third pregnancy when an earlier pregnancy has ended in stillbirth.

Our study evaluated how a history of stillbirth in either of the first two pregnancies affects the risk of having a stillbirth or other adverse pregnancy outcomes in the third subsequent pregnancy. We used the Swedish Medical Birth Register to define a population-based cohort of women who had at least three singleton births from 1973 to 2012. The exposure of interest was a history of stillbirth in either of the first two pregnancies. The primary outcome was subsequent stillbirth in the third pregnancy. Secondary outcomes included: preterm birth, preeclampsia, placental abruption and small-for-gestational-age infant. Adjusted logistic regression was performed including maternal age, body mass index, smoking, diabetes and hypertension. A sensitivity analysis was performed excluding stillbirths associated with congenital anomalies, pregestational and gestational diabetes, hypertension and preterm stillbirths. The study contained data on 1 316 175 births, including 8911 stillbirths. Compared with women who had two live births, the highest odds of stillbirth in the third pregnancy were observed in women who had two stillbirths (adjusted odds ratio [aOR] 11.40, 95% confidence interval [95% CI] 2.75-47.70), followed by those who had stillbirth in the second birth (live birth-stillbirth) (aOR 3.59, 95% CI 2.58-4.98), but the odds were still elevated in those whose first birth ended in stillbirth (stillbirth-live birth) (aOR 2.35, 1.68, 3.28). Preterm birth, pre-eclampsia and placental abruption followed a similar pattern. The odds of having a small-for-gestational-age infant were highest in women whose first birth ended in stillbirth (aOR 1.93, 95% CI 1.66-2.24). The increased odds of having a stillbirth in a third pregnancy when either of the earlier births ended in stillbirth remained when stillbirths associated with congenital anomalies, pregestational and gestational diabetes, hypertension or preterm stillbirths were excluded. However, when preterm stillbirths were excluded, the strength of the association was reduced. Even when they have had a live-born infant, women with a history of stillbirth have an increased risk of adverse pregnancy outcomes; this cannot be solely accounted for by the recurrence of congenital anomalies or maternal medical disorders. This suggests that women with a history of stillbirth should be offered additional surveillance for subsequent pregnancies.

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© 2023 The Authors. Acta Obstetricia et Gynecologica Scandinavica published by John Wiley & Sons Ltd on behalf of Nordic Federation of Societies of Obstetrics and Gynecology (NFOG).