A randomized controlled trial in rural Sarlahi District, Nepal enrolled 400 mother-infant pairs across four intervention groups to test fortified balanced energy-protein (BEP) supplementation during pregnancy, lactation, both, or neither. At 6 months, infants whose mothers received BEP through both periods scored a significant 2.12 points higher on Bayley-4 language scales (95% CI: 0.16–4.08), driven specifically by the expressive communication subtest. No significant effects emerged for cognitive, motor, or socioemotional domains in any single-period or dual-period comparison.
The finding is methodologically noteworthy because the interaction effect — not additive single-period gains — drove the language result, suggesting timing continuity may matter more than supplementation volume alone. This aligns with the broader neurodevelopmental literature showing the first 1,000 days as a sensitive window where cumulative nutritional adequacy shapes synaptic architecture and myelination. However, several limitations temper enthusiasm: the substudy enrolled only ~100 infants per group, the trial was unblinded, and Bayley-4 assessments at 6 months have modest predictive validity for school-age cognition. The 2.1-point language advantage, while statistically significant, sits near the threshold of clinical meaningfulness on a 100-point standardized scale. The absence of effects on cognition and motor domains may reflect true nullity or insufficient statistical power. Crucially, this is a preprint posted to medRxiv and has not yet undergone peer review — findings and effect estimates may shift. Follow-up assessments at 18–24 months would substantially clarify real-world developmental significance.
