Rapid increase in the body mass index of very preterm infants is a risk factor for iron deficiency during infancy

Iron deficiency (ID) in very preterm infants born at 28–32 weeks of gestational age (GA) can lower mental and motor test scores. This study aimed to determine whether the rapid growth of very preterm infants might be associated with ID. Among 134 very preterm born between January 2014 and December 2020 at Jeonbuk National University Hospital and discharged home, 93 were included in this study. Rapid BMI increase (RBI) was defined as a z-score difference of > 1 standard deviation between birth and 8 months. ID occurred in 23 of 93 (24.7%) infants at 8 months of corrected age (CA). ID was more common in the RBI group (50%) than in the non-RBI group (18.7%). In the multivariate logistic regression corrected for GA, infants small for gestational age (SGA) (odds ratio [OR] 6.06, 95% confidence interval [CI] 1.34–30.21) and RBI by z-score (OR 4.26, 95% CI 1.28–14.65) were identified as independent risk factors for ID at 8 months of CA. Conclusively, both SGA and RBI in the early life of very preterm were risk factors for ID at 8 months of CA.