Micronutrients, birth weight, and survival.

Maternal micronutrient requirements during pregnancy increase to meet the physiologic changes in gestation and fetal demands for growth and development. Maternal micronutrient deficiencies are high and coexist in many settings, likely influencing birth and newborn outcomes. The only recommendation for pregnancy currently exists for iron and folic acid use. Evidence is convincing that maternal iron supplementation will improve birth weight and perhaps gestational length. In one randomized trial, iron supplementation during pregnancy reduced child mortality in the offspring compared with the control group. Few other single micronutrients given antenatally, including vitamin A, zinc, and folic acid, have been systematically shown to confer such a benefit. A meta-analysis of 12 trials of multiple micronutrient supplementation compared with iron-folic acid reveals an overall 11% reduction in low birth weight but no effect on preterm birth and perinatal or neonatal survival. Currently, data are unconvincing for replacing supplementation of antenatal iron-folic acid with multiple micronutrients.