OBJECTIVE

To assess the impact on birth size and risk of low birth weight of alternative combinations of micronutrients given to pregnant women.

DESIGN

Double blind cluster randomised controlled trial.

SETTING

Rural community in south eastern Nepal.

PARTICIPANTS

4926 pregnant women and 4130 live born infants.

INTERVENTIONS

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 <2500 g.

RESULTS

Supplementation with maternal folic acid alone had no effect on birth size. Folic acid-iron increased mean birth weight by 37 g (95% confidence interval -16 g to 90 g) and reduced the percentage of low birthweight babies (<2500 g) 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 64 g (12 g to 115 g) 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.

CONCLUSIONS

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.