A new study published in PLOS Medicine finds that women who undergo a cesarean section with their first child may have a small, but significant increased risk of a subsequent stillbirth or ectopic pregnancy.
The research team, including Prof. Louise Kenny of University College Cork in Ireland, says their findings may have important implications for expectant mothers and health care professionals worldwide.
The rates of cesarean section (c-section) have increased significantly over the years. According to the Centers for Disease Control and Prevention (CDC), cesarean delivery rates soared by 60% between 1996 and 2009, from 20.7% of total births to 32.9%.
The procedure - which involves the delivery of a baby through a surgical incision in the mother's abdomen and uterus - has been associated with an array of subsequent health problems for the infant. Last year, Medical News Today reported on a study suggesting that babies born via c-section are five times more likely to develop allergies, while a more recent study found that the procedure may put the infant at higher risk of obesity as an adult.
But this latest research, funded by the National Perinatal Epidemiology Centre in Ireland, finds that having a c-section may also have an impact on subsequent pregnancies.
Danish national registry data used to estimate pregnancy outcome risks
To reach their findings, the team analyzed Danish national registry data involving 832,996 women who had their first live birth between 1982 and 2010.
Women who had a c-section for their first live birth had a 14% increased rate of stillbirth in their next pregnancy and a 9% increased risk of ectopic pregnancy, compared with women who had a vaginal delivery.
The women were divided into groups dependent on whether they had a c-section or vaginal delivery for their first live birth. All women were monitored until they had experienced either a second live birth, miscarriage, stillbirth or ectopic pregnancy.
Using statistical modeling, the team estimated the rate of pregnancy complications that occurred following a prior c-section and compared this with the rate of pregnancy complications that occurred following a prior vaginal delivery.
They found that the women who had a c-section for their first live birth had a 14% increased rate of stillbirth (an absolute risk increase of 0.03%) in their next pregnancy and a 9% increased risk of ectopic pregnancy (an absolute increased risk of 0.1%), compared with women who had a vaginal delivery in their first live birth.
The team says they found no increased rate of miscarriage in a second pregnancy among women who underwent a prior c-section.
'Increases small, but should be considered'
The researchers stress that although the risk increases are significant, they are small. For example, they show that every 3,000 c-sections would result in one extra stillbirth in a subsequent pregnancy.
They also acknowledge that a c-section can be a "vital intervention" and the likelihood of pregnancy complications could be reversed with the procedure. For example, they note that choosing an elective c-section may avoid fetal death as a result of a failed vaginal birth.
The researchers add:
"The findings of the current study are particularly important for expectant mothers as well as health care professionals as they highlight that although c-section rates are increasing significantly worldwide, there is no dangerously increased rate of subsequent stillbirth, miscarriage or ectopic pregnancy.
Furthermore, the findings will better inform women of the benefits and risks associated with all modes of delivery and help women and their partners make a more informed decision regarding mode of delivery based on their individual pregnancy circumstances."
However, they point out that while the increased risks are small, women should consider them when deciding whether to undergo a c-section without any medical necessity.
"Considering the important public health consequences of stillbirth and ectopic pregnancy," they conclude, "further large-scale research is warranted using large-scale data as in the current study, and in the absence of clinical trials to confirm the present study findings and add to the current recommendations for the management of pregnancy following c-section."
The study was subject to some limitations. For example, the team acknowledges that since the study spanned 3 decades, changes in prenatal and neonatal care, as well as changes in obstetric training and techniques, c-section rates and societal behavior, may have affected the results.