Modifying effects of wealth on the response to nutrient supplementation in pregnancy on birth weight, duration of gestation and perinatal mortality in rural western China: double-blind cluster randomized controlled trial.

BACKGROUND There have been few reports of differential responses to nutrition interventions in women and children from poor households. Women from poor households have greater nutritional risks and are potentially a target group for programmes. We assessed the modifying effects of household wealth on responses to micronutrient supplements in pregnancy on newborn anthropometry and perinatal mortality. METHODS A cluster randomized double-blind controlled trial conducted in two rural counties in northwestern China. All pregnant women in villages were randomly allocated from enrolment until delivery to daily supplementation with folic acid (control), iron/folic acid or multiple micronutrients (MMNs) with a recommended allowance of 15 vitamins and minerals. Wealth was based on a score from an inventory of household assets. RESULTS In the pregnant women from the poorest one-third of the households, MMN supplements significantly increased birth weight by 68 g [95% confidence interval (CI) 4-131 g], reduced low birth weight by 60% [relative risks (RRs) 0.40, 95% CI 0.21-0.78] and tended to reduce early neonatal mortality by 52% (RR 0.48, 95% CI 0.17-1.36) compared with folic acid. Iron/folic acid significantly increased the duration of gestation by 0.41 weeks (95% CI 0.18-0.65), reduced pre-term birth by 45% (RR 0.55, 95% CI 0.32-0.93) and significantly reduced early neonatal mortality by 90% (RR 0.10, 95% CI 0.01-0.79) compared with folic acid. Iron/folic acid and MMN supplements had no significant effects in women from wealthier households. CONCLUSIONS In rural China, women from the poorest households had the largest perinatal outcome responses to micronutrient supplementation. In these women, standard iron/folic acid provided more protection for neonatal survival than MMN supplements.