Current pregnancy weight gain recommendations for those with obesity may be set too high, with growing concerns about the need for guidelines tailored to obesity severity. This population-based cohort study investigated the safety of pregnancy weight gain or loss below current recommendations for those with obesity and assessed the necessity of distinct guidelines for different obesity classes.
Weight gain below current recommendations appears safe in pregnancies with obesity and may benefit women with class 3 obesity, highlighting the need for tailored guidelines for this group.
Current pregnancy weight gain recommendations for those with obesity may be set too high, with growing concerns about the need for guidelines tailored to obesity severity. This population-based cohort study investigated the safety of pregnancy weight gain or loss below current recommendations for those with obesity and assessed the necessity of distinct guidelines for different obesity classes.
Investigators analyzed pregnancies with obesity (body mass index ≥30 kg/m² before 14 weeks' gestation) via data from the Stockholm–Gotland Perinatal Cohort and Swedish national healthcare registers (2008–2019). Gestational weight gain, standardized into z-scores for gestational age, was assessed in relation to a composite adverse outcome, including stillbirth, unplanned cesarean delivery, infant mortality, gestational diabetes, abnormal birth weight, preterm birth, pre-eclampsia, excess postpartum weight retention, and new-onset maternal cardiometabolic disease.
Poisson regression was used for calculating rate ratios (RRs) for adverse outcomes along the weight gain z-score continuum, using the lower limit of US Institute of Medicine (IOM) recommendations (5 kg) as a reference. Analyses were adjusted for confounders like Nordic country of birth, cohabitation status, education level, pre-pregnancy cardiovascular disease or diabetes, smoking status, early pregnancy BMI, parity, height, and maternal age.
The cohort encompassed 11,667 individuals with class 1 obesity, 3,160 with class 2 obesity, and 933 with class 3 obesity, with 14%, 25%, and 33% respectively gaining less than the IOM recommendations. For class 1 and 2 obesity, weight gain below the IOM lower limit did not escalate the chances of adverse outcomes (e.g., RR = 0.97 [95% CI: 0.89–1.06] at a z-score of -2.4, equivalent to 0 kg weight gain in class 1 obesity).
In class 3 obesity, weight gain below the IOM recommendations was linked with minimized risks of adverse outcomes (e.g., RR = 0.81 [95% CI: 0.71–0.89] at a z-score of -2.4, equivalent to 0 kg weight gain).
The findings highlight the need to re-assess current IOM suggestions for pregnancy weight gain in those with obesity, suggesting lowering or removing the lower limit and introducing separate tailored guidelines for class 3 obesity. Such adjustments could help mitigate poor maternal and infant health outcomes related to pre-pregnancy obesity.
The Lancet
Safety of low weight gain or weight loss in pregnancies with class 1, 2, and 3 obesity: a population-based cohort study
Kari Johansson et al.
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