Impact of Exclusive Breastfeeding and Extrauterine Growth Restriction on Post-Discharge Growth in Preterm Infants: A Longitudinal Cohort Study in a Kangaroo Mother Care Program

Background/Objectives: Extrauterine growth restriction (EUGR) and exclusive breastfeeding (EBF) are critical factors influencing early post-discharge growth in preterm infants. Although EBF is recommended in Kangaroo Mother Care (KMC) programs, its association with early anthropometric recovery remains unclear. This study evaluated the association between EUGR at 40 weeks of corrected age and EBF at 40 weeks, 3 months, and 6 months with anthropometric growth and acute malnutrition in preterm infants during the first six months of corrected age. Methods: A retrospective longitudinal cohort study was conducted, including 117 preterm infants (≤34 weeks of gestation) enrolled in the KMC program. Changes in weight, length, and head circumference z-scores and the incidence of acute malnutrition were analyzed using generalized estimating equations (GEEs). EUGR was defined as weight <10th percentile at 40 weeks. Acute malnutrition was defined as a weight-for-length z-score ≤−2. Results: EUGR was observed in 23.9% of the infants. EBF prevalence was 53% at 40 weeks and 40% at three and six months, respectively. EBF at 40 weeks was associated with a reduced weight z-score (coefficient: −0.29; p = 0.030), EBF at 3 months increased the weight z-score (coefficient: 0.34; p = 0.014), and EBF at 6 months reduced the risk of acute malnutrition (coefficient: −1.02; p = 0.036). Infants with EUGR showed greater weight gain over time (coefficient: 0.37; p = 0.020) yet remained below their non-EUGR peers. Conclusions: EBF during the first six months post-discharge supports weight gain and reduces the risk of malnutrition. However, EBF at 40 weeks may not ensure the immediate recovery of weight. EUGR is a key determinant of early growth.