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.