Impact of pre-pregnant body mass index and gestational weight gain on the development of hypertensive disorders of pregnancy: the KODMO study.

Obese pregnant women are more likely to develop hypertensive disorders of pregnancy (HDP), which puts them at risk for future cardiovascular events and type 2 diabetes. This study aimed to investigate the relationship between body weight and HDP in nondiabetic singleton-pregnant women. We examined the KODMO database, which included 5,120 pregnant women who gave birth at NHO Kokura Medical Center between January 2009 and December 2019, excluding those with pre-existing diabetes mellitus, hypertension, or multiple pregnancies. A multivariate logistic regression analysis of potential HDP risk factors revealed that both pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) were independent risk factors. The estimated impact was considerably greater in women with higher pre-pregnancy BMI, with odds ratios of 1.60 (95% CI: 1.18-2.18, p = 0.0025) for obesity degree 1 (25 ≤ BMI < 30 kg/m²) and 3.42 (95% CI: 2.35-5.01, p < 0.0001) for obesity degree ≥2 (BMI ≥ 30 kg/m²) (reference: normal weight [18.5 ≤ BMI < 25 kg/m²]). GWG was further investigated by stratifying BMI categories, which revealed that obese pregnant women have a risk of developing HDP even with the normal GWG defined by current guidelines. The odds ratio of HDP in pregnant women with normal GWG was 1.79 (95% CI: 1.02-3.41, p = 0.0436) in obesity degree 1 and 3.25 (95% CI: 1.57-6.74, p < 0.0001) in obesity degree ≥2. The impact of GWG as a modifiable factor of HDP varies with pre-pregnancy BMI, highlighting the importance of weight management before and during pregnancy.