Introduction Current knowledge concerning the maternal-fetal outcomes of multiple repeated caesarean section (MRCS) is limited. No population-wide incidence studies of caesarean order have been undertaken.

Methods We identified all cases of women in the UK undergoing fifth or more caesarean section in 2009 using the UK Obstetric Surveillance System. Two women delivering by lower order repeat caesarean section in the same unit as each case were also recruited.

Results A total of 94 MRCS were reported, representing an estimated UK incidence of 1.20 per 10 000 maternities (95% CI 0.97 to 1.47). Women in the MRCS cohort who also had placenta praevia or accreta had significantly more major obstetric haemorrhages (MOH) RR 55.1 (95% CI 17.8 to 170.5), blood transfusions RR 51.3 (95% CI 16.5 to 160) and admissions to critical care RR 25.2 (95% CI 11.1 to 57.3), than women having lower order repeat caesareans. In the absence of praevia or accreta MRCS was still associated with MOH RR 2.56 (95% CI 1.41 to 4.66). Babies born to mothers having MRCS were more likely to be admitted to a NNU even after adjusting for prematurity aOR 3.85 (95% CI 1.67 to 8.91).

Conclusion The maternal morbidity associated with multiple repeat caesarean sections appears largely secondary to placenta praevia and accreta.