To assess the impact on birth size and risk of low birth weight of alternative combinations of micronutrients given to pregnant women.
Double blind cluster randomised controlled trial.
Rural community in south eastern Nepal.
4926 pregnant women and 4130 live born infants.
426 communities were randomised to five regimens in which pregnant women received daily supplements of folic acid, folic acid-iron, folic acid-iron-zinc, or multiple micronutrients all given with vitamin A, or vitamin A alone (control).
Main outcome measures
Birth weight, length, and head and chest circumference assessed within 72 hours of birth. Low birth weight was defined <2500g.
Supplementation with maternal folic acid alone had no effect on birth size. Folic acid-iron increased mean birth weight by 37g (95% confidence interval −16g to 90g) and reduced the percentage of low birthweight babies (<2500g) from 43% to 34% (16%; relative risk=0.84, 0.72 to 0.99). Folic acid-iron-zinc had no effect on birth size compared with controls. Multiple micronutrient supplementation increased birth weight by 64g (12g to 115g) and reduced the percentage of low birthweight babies by 14% (0.86, 0.74 to 0.99). None of the supplement combinations reduced the incidence of preterm births. Folic acid-iron and multiple micronutrients increased head and chest circumference of babies, but not length.
Antenatal folic acid-iron supplements modestly reduce the risk of low birth weight. Multiple micronutrients confer no additional benefit over folic acid-iron in reducing this risk.
What is already known on this topic
Deficiencies in micronutrients are common in women in developing countries and have been associated with low birth weight and preterm delivery
What this study adds
In rural Nepal maternal supplementation with folic acid-iron reduced the incidence of low birth weight by 16%
A multiple micronutrient supplement of 14 micronutrients, including folic acid, iron, and zinc, reduced low birth weight by 14%, thus conferring no advantage over folic acid-iron