Neither Preconceptional Weekly Multiple Micronutrient nor Iron-Folic Acid Supplements Affect Birth Size and Gestational Age Compared with a Folic Acid Supplement Alone in Rural Vietnamese Women: A Randomized Controlled Trial.

Double-blind randomized controlled trial in rural Vietnamese women of reproductive age who planned to become pregnant, conducted across 20 communes in Thai Nguyen province. The active intervention arms included MM (n = 525) and IFA (n = 515), with a weekly folic acid control arm.

Participants received weekly oral supplement capsules before conception, continuing through conception and pregnancy, for up to 2 years preconception. The active regimens were multiple micronutrients (including folic acid 2800 μg and iron as ferrous sulfate 60 mg, plus other micronutrients) or iron-folic acid (ferrous sulfate 60 mg plus folic acid 2800 μg), compared with folic acid alone (2800 μg); all were delivered as two capsules per weekly visit.

Weekly preconception multiple micronutrients or iron-folic acid did not improve birth size or gestational age versus folic acid alone. In the intention-to-treat analysis of 1,599 births, mean gestational age was 39.2 weeks in all groups (P = 0.99) and mean birth weight was 3083.1 g for MM, 3083.7 g for IFA, and 3064.5 g for FA (P = 0.72). Small for gestational age (12.4%, 10.2%, 12.2%), low birth weight (5.2%, 4.1%, 5.9%), and preterm birth were also not meaningfully different across groups. Per-protocol results among 824 births were likewise null, and there was no evidence that effects differed by baseline underweight or anemia.

The main findings were null despite a fairly large trial, and the per-protocol analysis was restricted to 824 births among women who received supplementing for at least 26 weeks preconception, reducing the analyzable sample. Birth outcomes depend on conception and pregnancy follow-up, so results are less informative for women who did not conceive or complete follow-up within the analysis window. Subgroup analyses did not identify a responsive underweight or anemic subgroup.