Growth Patterns in Preterm Children: Catch-Up Growth, Wasting, and Obesity Risk from the PERSIAN Birth Cohort neonatology

Background Childhood growth impairment, often due to undernutrition, increases long-term health risks. Preterm infants are especially vulnerable and require early support. Catch-up growth helps, but its optimal timing is unclear. This study examines preterm growth patterns to identify those at risk and guide intervention. Methods Using PERSIAN Birth Cohort data from four Iranian cities, we examined how preterm birth affects height-for-age (HAZ), weight-for-age (WAZ), weight-for-height (WHZ), BMI-for-age (BMI-Z), stunting, wasting, underweight, and obesity. Preterm status: term (≥۳۷ weeks), late (۳۴-۳۶), moderate (۳۲-۳۳), very/extremely (≤۳۲ weeks). Growth effects were assessed via Generalized Estimating Equations. Quantile regression examined preterm birth's effect across BMI-Z quantiles. Findings Among ۹,۰۱۵ pregnant Iranian women enrolled, ۷,۱۶۹ neonates were followed at ۲-۶۰ months. Preterm births were ۱۱.۰%: ۸.۸% late, ۱.۳% moderate, and ۰.۵% very/extremely preterm. By ۳۶ months, both late and moderate preterm children showed catch-up in HAZ, and by ۴۸ months, in WAZ, with no significant differences in stunting or underweight risk compared to full-term peers. In contrast, very/extremely preterm children had persistent HAZ and WAZ deficits and remained at higher risk of underweight, though stunting risk was no longer elevated. WHZ and BMI-Z declined with increasing prematurity and remained lower through ۶۰ months. Preterm birth was associated with higher odds of wasting and lower BMI-Z, with no significant difference in obesity risk. Interpretation Preterm children face persistent growth challenges, including an increased risk of wasting, despite similar HAZ and WAZ to full-term peers. These findings highlight the need for early, targeted nutritional interventions to prevent wasting and support optimal growth.