Is low weight gain or weight loss in pregnancies with class 1, 2, and 3 obesities safe?

Current gestational weight gain recommendations for women with obesity may be too high, and guidelines might need to vary based on the severity of obesity. A recent study investigated the safety of gestational weight gain below current recommendations or even weight loss in pregnancies with obesity, and evaluated whether different guidelines are needed for different obesity classes.

In this population-based cohort study, electronic medical records from the Stockholm–Gotland Perinatal Cohort study were employed –to identify pregnancies with obesity (early pregnancy BMI before 14 weeks' gestation ≥30 kg/m2) among singleton pregnancies delivered from 2008-2015. Pregnancy records were linked with Swedish national healthcare register data up to Dec 31, 2019. Gestational weight gain was calculated as the weight at delivery minus early pregnancy weight (<14 weeks gestation), standardized for gestational age into z-scores. Rate ratios (RRs) for the composite adverse outcome were compared with the current lower limit for gestational weight gain – recommended by the US Institute of Medicine (IOM; 5 kg at term), adjusted for confounding factors.

The cohort comprised 15,760 pregnancies with obesity––followed for a median of 7.9 years. Class 1 obesity accounted for 74.0% of the cases, class 2 obesity for 20.1%, and class 3 for 5.9%. Weight gain below the IOM recommendation (5 kg) occurred in 13.9%, 24.9%, and 33.2% of pregnancies in classes 1, 2, and 3, respectively. In classes 1 and 2 obesity, gestational weight gain below the IOM limit or weight loss did not increase the risk of the adverse composite outcome. In class 3 obesity, weight gain below the IOM limit or weight loss was associated with a reduced risk of the adverse composite outcome.

The results supportlowering or removing the lower limit of current IOM recommendations for pregnant women with obesity. The authors suggested that separate guidelines for class 3 obesity may be warranted.

Source: Johansson K, Bodnar LM, Stephansson O, et al. The Lancet. 2024 Apr 13;403(10435):1472-81.