Pre-pregnancy obesity, not gestational weight gain, is a high-risk factor for pre-eclampsia: a retrospective study in Bengbu, China

Objective To examine the prevalence of obesity among full-term pregnant women and investigate its etiological association with pre-eclampsia through a retrospective study. Methods Data from 2,153 singleton full-term pregnant women were categorized into four groups based on their pre-pregnancy body mass index (PBMI): Underweight, Healthy weight, Overweight, and Obesity. The incidence rate and relative risk of pre-eclampsia were calculated in each group. Gestational weight gain (GWG) was compared across groups, and women were classified as having no excess or excess GWG according to the 2009 Institute of Medicine guidelines. The proportion and relative risk of excess GWG were calculated for each group, as were the incidence rate and relative risk of pre-eclampsia in relation to excess GWG. The associations between pre-eclampsia severity and each of PBMI and GWG were assessed. Results The analysis revealed differential pre-eclampsia incidence across PBMI classifications: Underweight (2.78%), Healthy weight (4.66%), Overweight (13.97%), and Obesity (25.35%). Compared with Healthy weight, the relative risk (95% confidence intervals) of pre-eclampsia in Underweight, Overweight, and Obesity were 0.596 (0.262, 1.354), 2.996 (2.128, 4.219), and 5.436 (3.432, 8.621), respectively. Mean GWG was 15.22 ± 4.77 kg. GWG was significantly higher among Underweight and Healthy weight women than among Overweight and Obesity women (all P < 0.001). Excess GWG exhibited an ascending pattern across BMI categories: Underweight (27.31%), Healthy weight (41.31%), Overweight (63.01%), and Obesity (76.06%). Among the 2,153 pregnant women, PBMI was positively correlated with PE severity, whereas GWG showed no significant association. The estimated regression coefficients (95% confidence intervals) were 0.225 (0.179, 0.271) and −0.030 (−0.065, 0.005), respectively. Conclusions Pre-pregnancy obesity is a high-risk factor for pre-eclampsia, whereas an independent association with excessive gestational weight gain was not demonstrated in this cohort. Controlling pre-pregnancy obesity remains a key focus in obstetrics.