Cesarean Slightly Increases Future Risk for Stillbirth

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A prior caesarean section is associated with a small increased rate of subsequent stillbirth and ectopic pregnancy. The increased rate is confounded, however, by underlying medical conditions, as well as the indication for the primary caesarean delivery.

Sinéad M. O’Neill, MPH, from the National Perinatal Epidemiology Centre, Anu Research Centre, Department of Obstetrics and Gynaecology, Cork University Maternity Hospital, Ireland, and colleagues published the results of their population-based cohort study in the July issue of PLOS Medicine. They analyzed data from the Danish national register database, which used individuals’ unique civil personal registration numbers to create accurate linkage between and within registers. The researchers restricted the cohort to women who gave birth between 1982 and 2010 (n = 832,996).

Women with a prior caesarean section had a 14% increased hazard of subsequent stillbirth compared with women who had a spontaneous vaginal delivery. Women with a prior caesarean surgery had a moderately increased (9%) rate of ectopic pregnancy compared with women who had a spontaneous vaginal delivery. The authors found no increase in the hazard of subsequent miscarriage for women who had a prior caesarean section.

The authors emphasize that these results should be placed within the context that stillbirth and ectopic pregnancy are both rare pregnancy outcomes.

The authors also explain the difficulties in quantifying such complex relationships: “Whilst we were able to assess temporal changes in the current study, with data that spanned almost three decades (from 1982 to 2010), it must be acknowledged that many changes in prenatal and neonatal care, as well as changes in obstetric training and techniques, cesarean section rates, and societal behaviour, may have influenced the results. Residual confounding cannot be ruled out in the present study, as is the case with many epidemiological observational studies.”

Their results, however, are consistent with a recent systematic review and meta-analysis that explored the relationship between prior caesarean section delivery and the likelihood of subsequent stillbirth and miscarriage.

The investigators suggest the findings will help women and caregivers as they choose a mode of delivery. If women were not exposed to caesarean delivery, then the investigators predict that there would be a reduction of 0.023 stillbirths per 100 population.

This work was funded by the National Perinatal Epidemiology Centre, Cork, Ireland and conducted as part of the Health Research Board PhD Scholars program in Health Services Research.