Risk Factors for Early Neonatal Hypocalcemia in Preterm Neonates Born After 32 Weeks Gestation

<b>Background/Objectives</b>: Early neonatal hypocalcemia is a common metabolic disorder in premature neonates with various risk factors, including perinatal asphyxia and fetal growth restriction (FGR). We aimed to investigate the incidence of early neonatal hypocalcemia in preterm neonates with and without FGR and to explore several maternal and neonatal risk factors for early neonatal hypocalcemia. Cardiotocography (three-tiered fetal heart rate categorization) was a novel risk factor. <b>Materials and methods:</b> This was a secondary analysis of the retrospective, single-center, case-control study of neonates admitted to a neonatal intensive care unit (NICU) between January 2021 and December 2023. The study included 24 neonates with FGR and 124 control neonates without FGR born at 33 to 36 6/7 gestational weeks. <b>Results:</b> Total serum Ca was significantly lower in control neonates (2.042 (SD 0.208)) compared to neonates with FGR (2.178 (SD 0.180)) (<i>p</i> = 0.004), and early neonatal hypocalcemia was significantly higher in control neonates (42.75%) compared to neonates with FGR (4.35%) (<i>p</i> < 0.001). There was no statistical difference in acid base and blood gas analysis between FGR and control (<i>p</i> > 0.05). Logistic regression with the backward method showed that FGR reduces the probability of early neonatal hypocalcemia by 96.3% (t = 9.679, <i>p</i> = 0.001), and cesarean delivery increases it by 2.702 times (t = 6.963, <i>p</i> = 0.004). <b>Conclusions:</b> In this observational study, FGR was found to reduce and cesarean delivery was found to increase the probability of early neonatal hypocalcemia in moderate and late neonates. Clinicians should consider screening neonates born by cesarean delivery for early neonatal hypocalcemia. Three-tiered fetal heart rate categorization and acid base and blood gas analysis upon NICU admission cannot alert neonatologists to early neonatal hypocalcemia.