Postpregnancy BMI in the Progression From Hypertensive Disorders of Pregnancy to Type 2 Diabetes

OBJECTIVE To study the extent to which BMI after pregnancy adds to the elevated risk of postpregnancy type 2 diabetes in women with a history of hypertensive disorders of pregnancy (HDP) (preeclampsia or gestational hypertension). RESEARCH DESIGN AND METHODS We used data from the Nurses' Health Study II, a prospective cohort study. In women aged 45-54 years without prior gestational diabetes mellitus, we investigated the interaction between BMI and HDP history on the risk of type 2 diabetes. For clinical and public health relevance, we focused on additive interaction. The main outcome measure was the relative excess risk due to interaction calculated from multivariable Cox proportional hazardsmodels using normal weight as the reference group. RESULTS In total, 6,563 (11.7%) of 56,159 participants had a history of HDP and 1,341 women developed type 2 diabetes during 436,333 person-years. BMI was a strong risk factor for type 2 diabetes regardless of HDP history. However, there was evidence of an additive interaction between BMI and HDP for the risk of type 2 diabetes (P = 0.004). The attributable proportion of risk due to the interaction ranged from 0.12 (95% CI -0.22, 0.46) in women who were overweight to 0.36 (95% CI 0.13, 0.59) in women with obesity class I. CONCLUSIONS Maintaining a healthy weight may be of even greater importance in women with a history of HDP, compared with other women with a history of only normotensive pregnancies, to reduce midlife risk of type 2 diabetes.