BackgroundWhile the association of pre-pregnancy body mass index (BMI) and hypertensive disorders in pregnancy (HDP) is well documented, little is known about the relationship between pre-pregnancy weight change and HDP. We examined the impact of adult pre-pregnancy weight change on the development of HDP. MethodsWe included 2914 women, surveyed about every three years since 1996, from the 1973-78 cohort of the Australian Longitudinal Study on Women's Health. Women without hypertension or HDP were followed-up between 2003 and 2012. Generalised estimating equations were used to assess the effect of baseline BMI (mean age 20years) and pre-pregnancy weight change on the incidence of HDP. ResultsOver 9years of follow up, 301 incident HDP cases (6.3%) were reported from 4813 pregnancies. Overweight and obese women at the baseline survey were 1.67 (95% CI 1.3, 2.2) and 2.15 (95% CI 1.4, 3.3) times more likely to develop HDP than normal weight women, respectively. Compared with stable weight women, women with small (>1.5-2.5%) or moderate/high (>2.5%) annual weight gain had elevated risk of HDP (RR 1.67 95% CI 1.3, 2.2; RR 2.31, 95% CI 1.8, 3.0, respectively). Women who reported annual weight loss (>1.5%) between baseline and the average age of 24years were 46% (95% CI 0.4, 0.8) less likely to develop HDP. ConclusionsPre-pregnancy weight gain is associated with an increased risk of HDP, whereas early adult weight loss is associated with lower risk of HDP.