The Association of Fat Mass Deviation with Neonatal Morbidities in Preterm Infants

Background/Objectives: Evidence suggests that assessment of neonatal body fat mass (FM) may provide additional insight into the relationship between disrupted fetal growth and neonatal health outcomes. Our objective was to determine whether neonatal body composition parameters are associated with hypoglycemia, hypothermia, and respiratory distress syndrome. Methods: We conducted a prospective study of preterm neonates born at ≤37 weeks of gestational age. Body composition was measured in the first week of life with bioelectrical impedance analysis (BIA). Results: We studied 101 neonates of mean gestational age 32.2 ± 3.2 weeks and mean birth weight 1792 ± 706 g. Neonates with intrauterine growth restriction (IUGR) had a significantly lower FM percentage (6.8 ± 3.6 compared with 8.3 ± 3.6%, p = 0.038), and higher free-FM percentage (93.1 ± 3.6 compared with 91.6 ± 3.4%, p = 0.041), compared with non-IUGR neonates. Compared with neonates with normal FM, neonates with decreased FM presented higher rates of hypothermia (35% compared with 9%, p = 0.005), hypoglycemia (46% compared with 9%, p < 0.001), and respiratory distress syndrome (58% compared with 27%, p = 0.008). Decreased FM percentage was significantly associated with hypoglycemia (OR 8.06, 95%CI 2.49–26.08, p < 0.001), hypothermia (OR 8.11, 95%CI 2.24–29.32, p = 0.001), and respiratory distress syndrome (OR 13.90, 95%CI 4.07–27.42, p < 0.001) after adjusting for gestational age, sex, and antenatal steroid administration. Conclusions: Lower FM percentage showed stronger associations with common neonatal morbidities, compared with standard anthropometric measurements alone. When a low FM percentage is detected, even when birth weight is normal, neonates at risk of undernutrition-related morbidity may benefit from closer nutritional and metabolic monitoring.