RESUMEN
BACKGROUND: Fetal growth improves in pregnant women who take daily maternal multiple micronutrients [United Nations International Multiple Micronutrient Preparation (UNIMMAP)] rather than iron and folic acid (IFA) alone. OBJECTIVE: Our objective was to test whether such an effect was mediated by changes in concentrations of cord hormones. DESIGN: In a double-blind, controlled trial carried out in Burkina Faso, we randomly assigned 1426 pregnant women to receive UNIMMAP or IFA supplements. We measured concentrations of insulin-like growth factor I (IGF-I), leptin, insulin, free thyroxine, and cortisol in cord serum in a subsample of 294 live single newborns. We performed mediation analysis with an Aroian test. RESULTS: UNIMMAP supplementation had no significant effect on cord hormone concentrations. However, UNIMMAP supplementation significantly affected concentrations of IGF-I (+30%; 95% CI: 8%, 52%; P = 0.009) and leptin in male newborns. In these infants, 51.1% (P = 0.08) of the effect of UNIMMAP supplementation on birth weight was mediated through IGF-I, whereas for female newborns, this proportion was negligible. UNIMMAP supplementation also increased cortisol concentrations by 36% (P = 0.009) in cord blood in primiparae (P for interaction = 0.02). Growth-retarded infants had 41.2% lower IGF-I (P < 0.0001) and 27.3% lower leptin (P = 0.04) than did infants with normal growth. Offspring of primiparae had reduced IGF-I and insulin concentrations, and their cortisol concentrations were 25% higher (P = 0.05). Male newborns had lower concentrations of IGF-I, leptin, and insulin than did female newborns. CONCLUSIONS: UNIMMAP supplementation had sex-specific effects on cord IGF-I and leptin concentrations that were of unclear clinical significance. Other pathways may have been involved in the action of UNIMMAP on fetal growth. The specific hormonal pattern in primiparae could be related to constrained fetal growth. Confirmatory studies are warranted. This trial was registered at clinicaltrials.gov as NCT00642408.