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

objective: 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. Design: Non-blinded, randomised controlled study. Setting: Pregnant women received powdered milk during their health check-ups at 19 antenatal clinics and delivered at two maternity hospitals in Santiago, Chile. Subject: 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). Results: 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 <= 3000g (P = 0.015) and the incidence of preeclampsia (P = 0.015). Compliance with the experimental product was apparent from a haematological study of red-blood-cell folate at the end of pregnancy, which was performed in a 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 0.57cm (95% CI 0.19-0.96 cm; P = 0.003). Conclusions: The new intervention resulted in increased mean birth weight. Associations with gestation duration and most secondary outcomes need a larger sample size for confirmation.