The risk of maternal complications and preterm deliveries is significantly higher for women undergoing their fifth or more caesarean section, finds a new study published Oct. 31 in BJOG: An International Journal of Obstetrics and Gynaecology.

The study explored the incidence of UK women having Multiple Repeat Caesarean Sections (MRCS), defined as five or more, and the outcomes for them and their babies compared to women having their second to fourth caesarean section.

The researchers, from Imperial College Healthcare NHS Trust and the University of Oxford , estimate that the UK incidence of MRCS is 1.2 per 10,000 maternities. The study compared 94 women who were undergoing MRCS with 175 women having fewer caesarean sections.

The results show that women undergoing MRCS experience higher incidences of major obstetric haemorrhage (where blood loss exceeded 1500 mls), blood transfusions and admissions to a critical care setting.

In the MRCS group 18% of women had a major obstetric haemorrhage compared to 0.6% in women with fewer caesarean sections. In addition, 17% of women in the MRCS group received a blood transfusion compared to 1% in the comparison group.

The study also found that women in the MRCS group were five times more likely to have a preterm delivery with 24% delivering prior to the 37-week gestation period, compared to 5% from the comparison group.

Furthermore the study looked at women within the MRCS group who were also diagnosed with placenta praevia and/or placenta accreta, conditions where the placenta is abnormally positioned in the womb during pregnancy.

Of the MRCS group, 18% had either placenta praevia or accreta. Within this sub-group there was a further increase in maternal complications including major obstetric and postpartum haemorrhage, which resulted in 50% of the women requiring a hysterectomy and two thirds needing critical care after delivery.

Dr Mandish Dhanjal, Department of Obstetrics & Gynaecology, Imperial College Healthcare NHS Trust and co-author of the research said:

"Multiple repeat caesarean sections are an unusual occurrence and for most women the outcomes are very good. However there is a higher risk of maternal complications and preterm delivery compared to women having fewer caesareans.

"We also found that these risks were greatest in women undergoing MRCS who also had placenta praevia and placenta accreta. Obstetricians should be aware of this high risk group of women and work in multidisciplinary teams in order to optimise their management."

John Thorp, BJOG Deputy-Editor-in-Chief added: "It is important that both women and obstetricians are aware of the complications associated with repeat caesarean sections. All caesarean section procedures carry risks, some that are life-threatening. Larger studies are needed to look at this in more detail before firm recommendations are made about the maximum number of caesarean sections which should be performed."