Can information regarding the index stillbirth determine risk of adverse outcome in a subsequent pregnancy? Findings from a single-center cohort study

Introduction: Women with a history of stillbirth have an almost five-fold increased risk of stillbirth in a subsequent pregnancy, as well as increased risk of other adverse maternal and neonatal outcomes. The reasons for this association are not well understood but could relate to recurrent causes. We aimed to determine whether information from the time of index stillbirth, including cause, is associated with outcome of a subsequent pregnancy. 

Material and methods: A retrospective cohort study was conducted at a UK tertiary maternity center. Cases were included if stillbirth was investigated, subsequent pregnancy care was provided, and the birth occurred in the same unit. Data on maternal characteristics, findings of investigations, and classification of death using the ReCoDe system were extracted, and logistic regression was performed to determine whether these factors were associated with adverse outcome in the subsequent pregnancy. 

Results: In this cohort (n = 266), there were 69 adverse outcomes, including three perinatal deaths. Preterm delivery (16.2%) and birthweight <10th centile (12.4%) were the most common adverse outcomes. Of the preterm births, 69.8% were iatrogenic and 47% of these were due to abnormalities of fetal growth. On multivariate analysis women with a preexisting medical condition (adjusted odds ratio [aOR] 2.12, 95% CI 1.10-4.12) and those who smoked in their subsequent pregnancy (aOR 6.80, 95% CI 1.99-23.30) were at increased risk of adverse outcome. Neither ReCoDe classification of stillbirth (P =.61) nor gestation of stillbirth (P =.36) were associated with subsequent pregnancy outcome. Placental histopathological findings of maternal vascular malperfusion (aOR 11.34, 95% CI 2.20-58.62), fetal vascular malperfusion (aOR 9.27, 95% CI 1.09-78.82), and chorioamnionitis (aOR 6.35, 95% CI 1.16-34.78) in the index stillbirth were associated with adverse outcome in subsequent pregnancy. These associations were independent of maternal characteristics. 

Conclusions: Placental examination at time of stillbirth is important, as certain placental disorders inform the risk of adverse outcome in subsequent pregnancy. In this cohort, information regarding maternal characteristics and classification of cause of stillbirth do not provide significant prognostic information about the risk of adverse outcome in subsequent pregnancies. Optimal management of maternal medical disorders and access to smoking cessation are essential.