Effect of Omega-3 Supplementation in Pregnant Women with Obesity on Newborn Body Composition, Growth and Length of Gestation: A Randomized Controlled Pilot Study

Maternal obesity, a state of chronic low-grade metabolic inflammation, is a growing health burden associated with offspring adiposity, abnormal fetal growth and prematurity, which are all linked to adverse offspring cardiometabolic health. Higher intake of anti-inflammatory omega-3 (n-3) polyunsaturated fatty acids (PUFA) in pregnancy has been associated with lower adiposity, higher birthweight and longer gestation. However, the effects of n-3 supplementation specifically in pregnant women with overweight and obesity (OWOB) have not been explored. We conducted a pilot double-blind randomized controlled trial of 72 pregnant women with first trimester body mass index (BMI) ≥ 25 kg/m² to explore preliminary efficacy of n-3 supplementation. Participants were randomized to daily DHA plus EPA (2 g/d) or placebo (wheat germ oil) from 10-16 weeks gestation to delivery. Neonatal body composition, fetal growth and length of gestation were assessed. For the 48 dyads with outcome data, median (IQR) maternal BMI was 30.2 (28.2, 35.4) kg/m². In sex-adjusted analyses, n-3 supplementation was associated with higher neonatal fat-free mass (β: 218 g; 95% CI 49, 387) but not with % body fat or fat mass. Birthweight for gestational age z-score (-0.17 ± 0.67 vs. -0.61 ± 0.61 SD unit, p = 0.02) was higher, and gestation longer (40 (38.5, 40.1) vs. 39 (38, 39.4) weeks, p = 0.02), in the treatment vs. placebo group. Supplementation with n-3 PUFA in women with OWOB led to higher lean mass accrual at birth as well as improved fetal growth and longer gestation. Larger well-powered trials of n-3 PUFA supplementation specifically in pregnant women with OWOB should be conducted to confirm these findings and explore the long-term impact on offspring obesity and cardiometabolic health.