Trajectory and predictors of human milk intake from 1 to 8.5 months of lactation: findings from the multicenter Mothers, Infants, and Lactation Quality (MILQ) cohort study.

BACKGROUND

Understanding patterns and determinants of human milk (HM) intake in early infancy is important for supporting optimal practices; however, data are limited across diverse populations.

OBJECTIVES

This study aimed to describe the trajectory of HM intake (g/d) from 1 to 8.5 mo postpartum and to identify sociodemographic, maternal, infant, and breastfeeding-related predictors of HM intake.

METHODS

This multicenter cohort analysis from the Mothers, Infants, and Lactation Quality study included 665 healthy mother-infant dyads assessed at 1 to 3.49 mo (M1), 3.5 to 5.99 mo (M2), and 6 to 8.5 mo (M3) postpartum. HM intake was assessed at M1 to M3 using the dose-to-mother technique in Bangladesh, Brazil, and The Gambia, and 24-h test weighing in Denmark. Longitudinal mixed-effects models with linear and quadratic terms for postpartum time were used to examine HM intake trajectories and identify predictors. Interaction models were adjusted for maternal BMI (kg/m2), infant sex, exclusive breastfeeding (EBF) for 6 mo, and infant weight-for-age (WAZ) z-score. An additional model included breastfeeding frequency for 3 sites.

RESULTS

HM intake showed a significant nonlinear association over time (βquadratic = -0.62; 95% CI: -0.71, -0.52). Higher maternal BMI (β = -5.27; 95% CI: -8.54, -2.00), female infant sex (β = -38.19; 95% CI: -58.98, -17.39), and not being EBF for 6 mo (β = -50.81; 95% CI: -75.08, -26.54) were associated with lower HM intake, whereas higher infant WAZ was associated with higher intake (β = 78.36; 95% CI: 66.45, 90.28). Higher breastfeeding frequency was associated with greater HM intake (β = 6.32; 95% CI: 3.70, 8.93). EBF for 6 mo, infant WAZ, and breastfeeding frequency modified HM intake trajectories. EBF-related differences increased over time, whereas WAZ interaction attenuated and breastfeeding frequency interaction increased.

CONCLUSIONS

Maternal BMI, infant sex, EBF for 6 mo, WAZ, and breastfeeding frequency predict HM intake between 1 and 8.5 months of lactation, whereas EBF, WAZ, and breastfeeding frequency shape the HM intake trajectory. This trial was registered at clinicaltrials.gov as NCT03254329 (https://clinicaltrials.gov/study/NCT03254329).