Mortality, morbidity and growth among moderately low birthweight infants in India, Malawi, and Tanzania

Abstract

BACKGROUND: Despite notable global reductions in infant and under-five mortality over the last two decades, about half of the remaining neonatal deaths occur among low birth weight (LBW) infants. We conducted a prospective study to characterize the mortality risk and morbidity of moderately LBW (MLBW; 1500-2499 g birth weight) infants during the first year of life in India, Malawi, and Tanzania. METHODS: The multi-site Low Birthweight Infant Feeding Exploration (LIFE) study was conducted from September 2019 to July 2021 and followed a cohort of MLBW infants from India, Malawi, and Tanzania from birth to 52 weeks of age. At follow-up visits conducted at 1, 2, 4, 6, 10, 14, 18, 26, 39, and 52 weeks of age, mothers/caregivers were asked to recall the presence of diarrhea, fever, acute respiratory infections, and convulsions during the past week, and infant weight and length were assessed. Generalized estimating equations (GEE) were used to evaluate study site and sociodemographic risk factors for infant morbidity and mortality, and also to assess the relationship between infant morbidity and anthropometric measures. RESULTS: A total of 1,121 MLBW infants were included in the analysis and 47 (4.2%) deaths were recorded by the age of 12 months. Preterm-appropriate-for-gestational age infants had approximately twice the risk of infant death compared to term-small-for-gestational age infants (RR: 2.09; 95% CI: 1.08, 4.05). Period prevalence of diarrhea and fever increased with infant age and differed by study site (p-values < 0.05). In time-varying analyses, reported diarrhea during the past week was associated with lower length-for-age z-score (LAZ) (mean difference (MD): -0.20; 95% CI: -0.31, -0.09), weight-for-age z-score (WAZ) (MD: -0.25; 95% CI: -0.35, -0.16), and weight-for-length z-score (WLZ) (MD: -0.24; 95% CI: -0.36, -0.12), while fever was associated with lower WAZ (MD: -0.14; 95% CI: -0.21, -0.06), and WLZ (MD: -0.17; 95% CI: -0.26, -0.08) but not LAZ at the concurrent study visit. CONCLUSION: The risk of death during the first year of life is high for MLBW, but differs by the contribution of prematurity and size-for-gestational age. Interventions that reduce the incidence of diarrhea and fever may improve the growth of MLBW infants. TRIAL REGISTRATION: The LIFE study was registered with ClinicalTrials.gov (NCT04002908).