Objectives The aim of this study is to examine the hypothesis that mode of delivery at birth may be associated with metabolic disorders in adult midlife.

Setting Population cohort study

Participants The National Child Development Study consists of individuals born during 1 week in 1958 in Great Britain. Respondents with biomedical data on the metabolic syndrome at age 45 were included.

Outcome measure The metabolic syndrome was defined based on the National Cholesterol Education Program Adult Treatment Panel (NCEP-ATP) III classification.

Results 7156 were born naturally; among the caesarean births, 106 were non-elective and 85 were elective caesareans. The metabolic syndrome is present in 37.7% of those born by non-elective caesareans, 25.9% of those born by elective caesarean and 27.5% of those born by vaginal delivery. In a multivariate logistic regression model adjusted for antenatal factors, birth history, mother's characteristics and the socioeconomic environment at birth, only birth by non-elective caesarean remained associated with the metabolic syndrome in adulthood compared with vaginal delivery (OR 1.51, 95% CI 1.00 to 2.30). Mother's obesity (OR 1.61, 95% CI 1.12 to 2.34) and low maternal education level (OR 1.47, 95% CI 1.30 to 1.67) were also independently associated with midlife metabolic syndrome.

Conclusions Birth by non-elective caesarean in 1958 may be associated with metabolic syndrome in adulthood after adjusting for prior confounding factors. We suggest that the birth context of emergency caesareans in 1958 is suggestive of a ‘fetal stress’ mechanism affecting health across the lifecourse.