ESPE Yearbook of Paediatric Endocrinology

In Brief: The population-based Stockholm-Gotland Perinatal Cohort study analysed electronic medical records on 15 760 pregnancies with obesity, followed up for a median of 7.9 years. In pregnancies with class 1 or 2 obesity, low gestational weight gain (GWG, mean 0 kg at 40 weeks) did not increase risk of the adverse composite outcome (class 1: adjusted RR 0.97 [95% CI 0.89–1.06]; class 2: 0.96 [0.86–1.08]). In pregnancies with class 3 obesity, low GWG (mean 0 kg at 40 weeks) was associated with reduced risk of the adverse composite outcome (adjusted RR 0.81 [0.71–0.89]).

There are sparse data to inform the limits of healthy GWG. Possibly the only national guidelines (since used by several other countries) were published in 2009 by the US Institute of Medicine (IOM, currently the National Academy of Medicine). Those were based on risks for maternal postpartum weight retention, cesarean delivery, size at birth (SGA and LGA), preterm birth and childhood obesity. They stated that for women with pre-pregnancy obesity, GWG should be 11–20 pounds (5–9 kg), which was less than the previous IOM 1990 recommendation of ‘at least 15 pounds’ (~7 kg).

However, many women now start pregnancy with extremely high body mass index (BMI), and we now know this has a much larger impact than GWG on risks of gestational diabetes, pre-eclampsia and other adverse pregnancy outcomes. Importantly, it is currently unknown whether such women can safely avoid GWG or even reduce weight during pregnancy. The 2009 IOM committee acknowledged that most of their available data were on women with only class 1 obesity (BMI 30–34.9) and they had very few who showed GWG <5 kg.

This current large Swedish study fills this crucial evidence gap. Among women with pre-pregnancy class 1, class 2 (BMI 35–39.9), or class 3 (40+) obesity, 13.9%, 24.9%, and 33.2%, respectively, showed GWG below the 2009 IOM lower limit (5 kg). Furthermore, they extended the range of adverse outcomes beyond those considered by the 2009 IOM, to also include stillbirth, infant death, gestational diabetes, pre-eclampsia, and new-onset longer-term maternal cardiometabolic disease after pregnancy, and weighted these to reflect their severity.

These findings will hopefully support new guidelines to lower or remove the lower limit of GWG for pregnant women with obesity and enable appropriate dietary and lifestyle advice.