Women who have had emergency Caesarean section and a subsequent preterm birth or miscarriage are more likely to go into early labour during their third pregnancy, a study has found.

The research showed that treatments such as a cervical stitch do not reduce the risk.

The study, supported by our BRC, was part of our Women and Children’s Health Theme and our Precision Medicine Cluster.

Preterm birth has long term health consequences and puts an infant’s survival and quality of life at risk. It is projected to cost health services in England and Wales £939 million per year.

Research has shown that women who have had an emergency Caesarean section are at increased risk of late miscarriage or preterm labour. This risk is greater the further on in labour the Caesarean is done. There is a six-fold increased risk if performed in late labour when the neck of the womb is fully dilated.

In 2017-18, 28% of births in the UK were by Caesarean section, and more than half (16.2%) were emergency. A cervical stitch following Caesarean section can help to keep the neck of the womb closed during later pregnancies. This means the cervix is less likely to open, reducing the chances of going into early labour.

The study used data from patients at the Preterm Surveillance Clinic at St Thomas’ Hospital. The team examined the outcomes of 209 women who had a previous emergency Caesarean and a subsequent preterm birth. Of these 72 women required a cerclage (cervical stitch) and 33 (46%) delivered before 30 weeks gestation.

The researchers compared these results to a control group who received cerclage and delivered after 24 weeks. They found that those who had had a Caesarean were ten times more likely to deliver before 30 weeks (3% vs 30%). The results were similar whether the Caesarean was done in early or late labour. Even when the team did not include those women who did not receive cerclage in the analysis, 50% (53/107) delivered early before 37 weeks gestation.

Lead author Andrew Shennan is Professor of Obstetrics at King’s College London. He said: “This is a serious problem that few doctors are aware of. Recurrent preterm birth is more common and occurs early in women with prior emergency Caesareans but is difficult to treat. The recent escalation of Caesarean sections should be looked at critically, as some harm is evident.”

The authors suggest higher incisions in the uterus at Caesarean to help to prevent this problem. They also highlight that Caesarean sections may not always be safer then assisted vaginal deliveries.