Caesarean section is associated with a slightly increased rate of subsequent stillbirth and ectopic pregnancy, according to a large study of women living in Demark, published in this week in PLOS Medicine. Given the global increase in Caesarean rates, the results of the study, which was conducted by Louise Kenny and colleagues from University College Cork, Ireland and Aarhus University, Denmark, are of interest to pregnant women, their partners, and healthcare providers.
The researchers obtained data for 832,996 women from Danish national registers regarding their first live birth, including whether they had a Caesarean section, and then followed the women until they had a stillbirth, miscarriage, ectopic pregnancy or a second live birth. The researchers then used statistical modelling to estimate the rate of the pregnancy complications following a prior Caesarean section compared to prior vaginal delivery. The analyses were controlled for the possibility that Caesarean sections were performed because of complications affecting the earlier pregnancy.
The authors found women who had a Caesarean section had a 14% increased rate of stillbirth in their next pregnancy compared to women who had a vaginal delivery, corresponding to an absolute risk increase of 0.03%. In other words, performing approximately 3000 Caesarian sections would result in one extra stillbirth in a subsequent pregnancy. Compared to vaginal delivery, having a Caesarean section increased the risk of a subsequent ectopic pregnancy by 9% (an absolute risk increase of 0.1% and a number needed to harm of 1000) but did not increase the rate of subsequent miscarriages.
The authors are keen to reassure expectant mothers that the overall risk of a subsequent stillbirth or ectopic pregnancy, although elevated, remains small, and stress the need to put their findings in context. Professor Kenny said: "The findings of the current study are particularly important for expectant mothers as well as healthcare professionals as Caesarean section rates are increasing significantly worldwide. Whilst we showed that a previous Caesarean section is associated with a subsequent stillbirth and ectopic pregnancy, the overall risk of either is very low."
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O'Neill SM, Agerbo E, Kenny LC, Henriksen TB, Kearney PM, et al. (2014) Cesarean Section and Rate of Subsequent Stillbirth, Miscarriage, and Ectopic Pregnancy: A Danish Register-Based Cohort Study. PLoS Med 11(7): e1001670. DOI: 10.1371/journal.pmed.1001670