Total gestational weight gain and the risk of preeclampsia by pre-pregnancy body mass index categories: a population-based cohort study from 2013 to 2017.

Background Identifying the risk factors for preeclampsia (PE) is essential for the implementation of preventive actions. In the present study, we aimed at exploring the association between total gestational weight gain (GWG) and PE. Methods We performed a population-based cohort survey of 98,820 women with singleton pregnancies who delivered in Slovenia from 2013 to 2017. Aggregated data were obtained from the National Perinatal Information System (NPIS). The main outcome measure was the incidence of PE. The main exposure variable was total GWG standardized for the gestational duration by calculating the z-scores. The associations between total GWG and PE stratified by pre-pregnancy body mass index (BMI) categories adjusted for a variety of covariates were determined using multivariable logistic regression. We calculated the crude odds ratio (OR) and adjusted odds ratio (aOR) with a 95% confidence interval using a two-way test. Results Excessive GWG was associated with increased odds of PE in all pre-pregnancy BMI categories. The increase in the odds of PE by 445% was the highest in underweight women and by 122% was the lowest in obese women. Low GWG was associated with decreased odds of PE in all pre-pregnancy BMI categories except in normal-weight women with a GWG below -2 standard deviation (SD) and underweight women. The decrease in the odds of PE by 67% was the highest in obese women and by 41% was the lowest in normal-weight women. Conclusion Excessive GWG is a significant risk factor for PE, especially in underweight women, while low GWG is an important protective factor against PE, especially in obese women.