Small at Birth, Stunted for Life: Do Postnatal Interventions for Low-Birth-Weight Infants Improve Child Growth?

Low birth weight remains a leading risk factor for child growth faltering and early-life morbidity worldwide, prompting many low- and middle-income countries to adopt targeted newborn care policies that intensify postnatal support for at-risk infants. This study evaluates whether such policy targeting translates into measurable improvements in child growth, using evidence from Zambia’s 2014 Essential Newborn Care (ENC) Policy, which expanded postnatal interventions for infants born below 2,500 grams. We draw on pooled data from the Zambia Demographic and Health Surveys (2007–2018), focusing on children aged 0–59 months with valid birthweight and anthropometric measurements. Our empirical strategy employs a regression discontinuity difference-in-differences (RD-DID) design that exploits the sharp eligibility threshold at 2,500 grams and compares changes in the discontinuity before and after the policy rollout. We estimate local linear RD-DID models across multiple bandwidths and account for birth heaping through donut and jittering adjustments. We find steep birthweight gradients in stunting and related outcomes, underscoring the vulnerability of low-birth-weights infants. However, we find little evidence that the policy led to meaningful improvements in child growth at the eligibility cutoff. Estimated effects on stunting, underweight, wasting, thinness and diarrhoea morbidity are consistently small, imprecisely estimated, and statistically insignificant across a wide range of specifications. Taken together, the findings suggest that, in its current form, Zambia’s low-birth-weight newborn care policy has generated limited gains in early-life growth, underscoring potential gaps between policy design, implementation, and effective delivery of postnatal care in resource-constrained settings.