The effectiveness of ω-3 polyunsaturated fatty acid interventions during pregnancy on obesity measures in the offspring: an up-to-date systematic review and meta-analysis

Pregnant women and their offspring. Included healthy pregnancies and high-risk groups (e.g., obesity or history of gestational diabetes). Parallel-group randomized controlled trials (mostly two-armed; some three-armed); some open-label or double-blind. Follow-up durations ranged from 6 months to 19 years.

Prenatal omega-3 long-chain polyunsaturated fatty acid (LCPUFA) supplementation during pregnancy delivered orally via fish oil, cod liver oil, or algal DHA; regimens varied by trial (DHA +/- EPA; some combinations with vitamins/minerals); durations generally from mid-pregnancy (roughly 15–22 weeks) to delivery, with some continuing postnatally for several months.

Across 11 randomized trials (ten unique trials) with 3,644 offspring, prenatal omega-3 LCPUFA supplementation did not reduce obesity risk. Pooled effects showed no significant differences in BMI (SMD −0.001, 95% CI −0.08 to 0.08; n=2,051), BMI-Z (SMD 0.082, 95% CI −0.077 to 0.24; n=2,511), sum of skinfold thickness (SMD 0.09, 95% CI −0.33 to 0.53; n=227), body fat (%) (SMD 0.00, 95% CI −0.09 to 0.09; n=1,641), or fat mass (kg) (SMD 0.01, 95% CI −0.08 to 0.10; n=1,641). Weight and height showed no meaningful benefit; weight Z-score and height Z-score similarly showed no effect. Long-term benefits remain unclear due to heterogeneity and limited power. Large, high-quality RCTs are needed to assess potential subgroups (e.g., EPA vs DHA) and the role of dietary omega-6/omega-3 balance.

Major heterogeneity across trials in dosage, timing, formulations and outcomes; small to moderate sample sizes with high attrition; many trials not originally designed to assess obesity outcomes; inconsistent measurement methods and follow-up durations; some risk of bias in multiple domains.