Effects of a dairy product fortified with multiple micronutrients and omega-3 fatty acids on birth weight and gestation duration in pregnant Chilean women

The objective was to test the hypothesis that maternal food fortification with omega-3 fatty acids and multiple micronutrients increases birth weight and gestation duration as primary outcomes. The design was non-blinded randomised controlled study. Pregnant women received powdered milk during their health check-ups at 19 antenatal clinics and delivered at two maternity hospitals in Santiago Chile. Pregnant women were assigned to receive regular powdered milk (n = 477) or a milk product fortified with multiple micronutrients and omega-3 fatty acids (n = 495). Intention-to-treat analysis showed that mean birth weight was higher in the intervention group than in controls (65.4 g difference 95% confidence interval (CI) 5-126 g; P = 0.03) and the incidence of very preterm birth (< 34 weeks) was lower (0.4% vs. 2.1%; P = 0.03). On-treatment analysis showed a mean birth weight difference of 118 g (95% CI 47-190 g; P = 0.001) and a relative fall in both the proportion of birth weight sub-sample. In both types of analyses positive differences were also present for mean gestation duration birth length and head circumference. Nevertheless the relatively small sample sizes allowed a statistical power of .0.80 just for mean birth weight and birth length in the on-treatment analysis; birth length in that analysis had a difference of 0.57 cm (95% CI 0.19-0.96 cm; P = 0.003). The new intervention resulted in increased mean birth weight. Associations with gestation duration and most secondary outcomes need a larger sample size for confirmation. (authors)