Effects of docosahexaenoic acid supplementation during pregnancy on gestational age and size at birth: Randomized, double-blind, placebo-controlled trial in Mexico

Background. The need for omega-3 fatty acids, especially docosahexaenoic acid (DHA), during pregnancy has received much attention, but evidence of effects on birth outcomes is limited. Objective. To evaluate whether prenatal DHA supplementation increases gestational age and birth size. Methods. We conducted a double-blind, randomized, placebo-controlled trial in Cuernavaca, Mexico. We randomly assigned 1,094 pregnant women (18 to 35 years of age; median DHA dietary intake, 55 mg/day) to 400 mg/day of algal DHA or placebo from 18 to 22 weeks of gestation through delivery. Birth outcomes (968 live births and 5 stillbirths) were ascertained from hospital records within 24 hours of delivery. Results. Intention-to-treat analysis showed no differences between the control and DHA group (all p > .05) in mean gestational age (39.1 + 1.7 and 39.0 +/- 1.9 weeks, respectively), weight (3.20 + 0.47 and 3.21 +/- 0.45 kg, respectively), length (50.3 +/- 2.7 and 50.3 +/- 2.3 cm, respectively) and head circumference (34.3 +/- 1.8 and 34.3 +/- 1.5 cm, respectively) at birth. Offspring of supplemented primigravidae (n = 370) were heavier (difference, 99.4 g; 95% CI, 5.5 to 193.4) and had larger head circumferences (difference, 0.5 cm; 95% CI, 0.1 to 0.9) than controls; the differences in multigravidae (n = 603) were -53.3 g (95% CI, -126.8 to 20.2) and -0.2 cm (95% CI, -0.4 to 0.1), respectively (p < .05 for heterogeneity). Conclusions. Prenatal DHA supplementation of primigravid women may result in increased birth size in a population where dietary DHA intakes are very low. Benefits of the intervention on infant health and neurodevelopment are under study.