Discussion

Main Findings

In the present study, we assessed the association between CD and subsequent stillbirth, and the impact of VBAC on stillbirth using data from Swedish MBR. The results show that women with a prior CD had an increased risk of subsequent stillbirth by 37%, and the risk was similar for both pre-labour CD (31% increase) and in-labour CD (36% increase). Pre-labour CD was associated with subsequent intrapartum stillbirth, but not in-labour CD. We also found an increased odds of antepartum stillbirth in women who had VBAC (compared to women who had a repeat CD), but no increased odds for intrapartum stillbirth in this group.

Strengths and limitations

The strengths of the present study include the use of national register-based data and the ability to make a linkage between registers which minimises risk of selection bias. As this is one of the largest studies investigating the risk of stillbirth following a previous CD, we were also able to conduct several subgroup and sensitivity analyses. We further classify stillbirth based on timing into antepartum and intrapartum stillbirth, as well as into explained and unexplained stillbirths. We restricted the analyses to singletons because CD and pregnancy complications related to stillbirth are more common in multiple gestations35. We also restricted the analyses to mothers who had live births in their first pregnancy since women with a history of stillbirth have nearly 5 times higher risk of subsequent stillbirth21. Limitations to the study include the possibility of misclassification for data on the clinical conditions (explaining cause of stillbirth) since data on some conditions, such as vasa praevia, were only available in ICD-9 and ICD-10. Other limitations related to unmeasured confounders as this is an observational study.