Previous research has suggested that cesarean section may be associated with an increased risk of developing obesity in childhood, adolescence and adulthood. Yet, previous studies have been small or unable to differentiate between elective and non-elective cesarean section. Therefore, using a population-based cohort the purpose is to examine the associations between vaginal delivery, elective and non-elective cesarean section on the risk of developing obesity in young adulthood among Swedish young singleton males. Using the Swedish medical birth registry, the recorded mode of delivery and indication of delivery which will be matched to those males who perform military conscription, where their body mass index is recorded. The investigators hypothesize that there will be an elevated risk of obesity in those born with non-elective cesarean section, as a function of confounding, while those born with elective cesarean section will not have a higher risk of obesity than those born with vaginal delivery.

Inclusion Criteria:

• Singleton birth.
• Retrievable from medical birth registry.

Exclusion Criteria:

• No available information on mode of delivery.
• Not conscripted.
• Extreme values at conscription.

All singleton born in Sweden between 1982 and 1987.