Prenatal Docosahexaenoic Acid Supplementation and Offspring Development at 18 Months: Randomized Controlled Trial

Randomized controlled trial in pregnant women receiving routine prenatal care in Cuernavaca, Mexico, with very low dietary intake of preformed DHA. For the DHA group, 365 participants were in the final analytic sample, and infants were followed to 18 months of age.

Pregnant participants in the active arm received oral algal docosahexaenoic acid (DHA) at a dose of 2 capsules containing 200 mg each daily, taken together once per day. Supplementation began between gestational weeks 18 and 22 and continued through delivery, and it was compared with placebo.

Prenatal DHA did not improve overall infant development at 18 months. On the Bayley Scales of Infant Development-II, the Mental Development Index was 94.3 (10.7) with DHA versus 95.2 (9.3) with placebo, with an adjusted difference of -1.00 (-2.42, 0.42); the Psychomotor Development Index was 93.0 (8.9) versus 93.3 (9.8), adjusted difference -0.46 (-1.80, 0.88). Behavior Rating Scale scores were essentially identical (111.5 vs 111.5; adjusted difference -0.01 [-0.95, 0.93]). Post-hoc analyses suggested possible benefit in less responsive or less stimulating home environments, but the primary overall effect was null.

The primary findings were null, and the subgroup signals were post-hoc and therefore hypothesis-generating only. Follow-up extended only to 18 months, limiting inference about longer-term neurodevelopment. Generalizability is constrained by the single-city Mexican setting and the low baseline DHA intake of the study population.