Parity and risk of diabetes in a Danish nationwide birth cohort.

P>Aims The purpose was to elucidate the association between parity and the incidence of diabetes using national register data. Methods The study population consisted of all Danish women with a singleton delivery in 1982/1983 (n = 100 669), who subsequently had 74 966 deliveries. The included women were followed up via registries until the end of 2006 for subsequent deliveries, diagnosis of diabetes and death/emigration. Results A total of 2021 cases (2.0%) were diagnosed with diabetes in connection with hospitalization or outpatient treatment during follow-up. Analyses were adjusted for fetal weight and duration of gestation, both at index pregnancy. Cox regression analysis with parity as a time-varying exposure, stratified in two age groups, showed an association between parity and risk of a diagnosis of diabetes. In women < 33 years of age, parity 2, 3 and 4 + were associated with an increased risk of being diagnosed with diabetes compared with parity 1 [relative risks: 1.6 (95% confidence interval 1.1-2.3), 2.8 (1.8-4.3) and 2.5 (1.3-4.8), respectively]. Among women > 33 years of age, parity 2 was associated with a significantly lower risk of diabetes diagnosis compared with parity 1, whereas parity 4 + was associated with a significantly higher risk of diabetes diagnosis compared with parity 1. Conclusions The study shows that the risk of diabetes diagnosis increases with parity in young Danish women. This may support a causal association between diabetes and parity.