Weight loss, stability and low weight gain during pregnancy among individuals with obesity: associations with adverse perinatal outcomes: an observational study

The safety of weight loss and low weight gain during pregnancy remains unclear. To determine how different patterns of gestational weight gain (GWG), including weight loss, stability and low GWG relate to perinatal outcomes by prepregnancy obesity class. The study population included 29,408 singleton livebirths among pregnant people with obesity from Kaiser Permanente Northern California (2008-2013). Clinically measured gestational weight gain was grouped into meaningful categories [Adequate (reference, met 2009 National Academy of Medicine (NAM) Guidelines (5-9.1 kg)), Excessive (>9.1 kg), Low (1-4.9 kg), Stable (+/-1 kg), Weight Loss (>1 kg)] or gestational weight gain z-score quintiles. Modified Poisson regression was used to estimate risk of adverse outcomes, stratified by obesity class. Electronic health record data were used to define outcomes, including Caesarean delivery, preterm birth, admission to the NICU, small and large for gestational age infants. Prevalence of weight stability and weight loss was 3.8% and 3.4%, respectively. Compared to those who gained within NAM, increased risk of small-for-gestational age was observed among those with weight loss among obesity class I (RR: 1.57, 95% CI: 1.12, 2.19), obesity class II (RR: 2.18, 95% CI: 1.52, 3.13) and obesity class III (RR: 1.72, 95% CI: 1.21, 2.45). Weight loss was associated with a decreased risk of Caesarean delivery among obesity class III, compared to NAM. Weight loss during pregnancy is associated with increased risk of small for gestational age among all obesity classes, but not other adverse perinatal outcomes, and may reduce risk of Caesarean delivery. Low weight gain and weight stability are not associated with risk of adverse outcomes among those with class III obesity. GWG guidelines may need to vary by obesity class.

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