Mediators of the Effect of Multiple Micronutrient Supplementation in Pregnancy on Infant Mortality in Tanzania (P24-050-19)

Abstract

Abstract Objectives Maternal micronutrient supplementation (MMS) in pregnancy has been shown to improve birthweight among infants in low- and middle-income countries (LMIC). Recent evidence also suggests that the survival benefits of MMS are greater for female infants as compared to males, but the biological mechanisms leading to the differential effect remain unclear. The objective of this study was to conduct a causal mediation analysis to examine the mechanisms through which MMS may operate on infant mortality. Haider BA, Bhutta ZA. Multiple-micronutrient supplementation for women during pregnancy. Cochrane Database Syst Rev. 2017;4: CD004905 Methods We utilized data from a randomized, double-blind, placebo-controlled trial of MMS conducted in Tanzania to examine mediators of the effect of MMS on six-week infant mortality. Causal mediation analyses were conducted for assessing the contributions of MMS on survival via their effects on birthweight, gestational age, weight-for-gestational age, and the joint effect of gestational age and weight-for-gestational age. Results Among 7486 participants (3762 randomized to MMS, 3724 randomized to placebo), we observed that the effect of MMS on survival was fully mediated through the joint effect of gestational age and weight-for-gestational age. Further, when analyses were stratified by sex, gestational age and weight-for-gestational age fully mediated the survival benefits for female infants while these factors accounted for only 34% of the effect among male infants. Conclusions We determined that increases in gestational age and birth weight fully mediate the beneficial effect of MMS on mortality among female infants; however, these mechanisms do not appear to be major contributors to a potential effect among males. Funding Sources This research was supported in part by the National Institutes of Health (NIH) predoctoral training grants, and was a secondary analysis of data from a study supported by a grant from the National Institute of Child Health and Human Development.