We conducted a prevalence study to examine the association between Caesarean section and body mass index (BMI) in 21,051 adult Danish men born in 1977-1983 who presented for mandatory conscription evaluation around age 18 years.

Design and methods:

Data on BMI from conscription records were linked to the men's birth records to identify mode of delivery and other perinatal data.


Two thousand one hundred thirty-eight men (10%) had been delivered by a Caesarean section. Prevalence of obesity at conscription was 6% for those born vaginally and 9% for those born by a Caesarean section. The adjusted prevalence ratio (PR) for obesity (BMI ≥ 30 kg/m2) was 1.35 (95% CI 1.14-1.60); the adjusted PR for overweight (25 ≤ BMI < 30 kg/m2) was 1.05 (95% CI 0.94-1.17). The adjusted mean difference in BMI was 0.38 kg/m2 (95% CI 0.16-0.60) comparing men born by Caesarean versus vaginal delivery. The estimates were similar for planned and nonplanned Caesarean deliveries.


Birth by a Caesarean section was associated with an increased risk of obesity among men.