A 17 year study published in the August edition of the British Journal of Obstetrics and Gynaecology has reported that following delivery by caesarean section, fewer women went on to have another pregnancy and the average length of time until the next pregnancy was greater, compared to those who had a spontaneous vaginal delivery.
The study followed 25,371 women who had delivered at the Aberdeen Maternity Hospital between 1980 and 1997 and showed that women who had undergone a caesarean section were less likely to have had a subsequent pregnancy. Just 66.9% of those who had a caesarean section went on to have a further pregnancy, compared with 71.6% who had had an instrumental vaginal delivery and 73.9% who had had a spontaneous vaginal delivery. Whether or not the caesarean was elective or emergency had no bearing on the incidence of subsequent pregnancy.
The average length of time to the next pregnancy following a caesarean section was 36.3 months compared with 31.8 months following an instrumental vaginal delivery and 30.4 months following a spontaneous vaginal delivery.
Women who delivered by caesarean section were also more likely to have an ectopic in their next pregnancy compared with women who had delivered spontaneously (9.5 per 1000 pregnancies compared to 5.7 per 1000 pregnancies)
All the information was then compared to a similar study* conducted at the same hospital but from 1964 to 1983. The current study suggests that the difference in incidence of subsequent pregnancy between caesarean section and spontaneous vaginal delivery is smaller than that previously reported. Overall, a greater proportion of women had a subsequent pregnancy in the current study compared with the Hall study (72% vs 68.0%).
Jill Mollison, lead author said: “This study highlights an association between mode of delivery and subsequent pregnancy. This is an important finding against the background of rising caesarean section rates.
"Future studies should focus on exploring whether failure to conceive is due to voluntary or involuntary factors and compare this across different modes of delivery.”
Dr Siladitya Bhattacharya, Honorary Consultant, and Reader at the University of Aberdeen and acting head of the University's Department of Obstetrics and Gynaecology, co-ordinated this study.
He said: "These results confirm the findings of a previous similar study* conducted in Aberdeen and highlight the potential long term effects of caesarean section on future reproduction.
"Studies such as these are facilitated by the unique nature of the Aberdeen Maternity Neonatal Databank (AMND) which links all the obstetric and fertility-related events occurring to women from a defined population in Grampian."
Mr Peter Bowen-Simpkins from the RCOG added: "Those involved in the delivery of obstetric care should be aware of the association and consider its implications when making a decision to perform a caesarean section."
*Hall et al Mode of delivery and future fertility (BJOG 1989)