Early Neonatal Predictors of Neonatal Hypocalcemia in Infants of Diabetic Mothers: An Epidemiologic Study

Prematurity, neonatal asphyxia, hypomagnesemia, and advanced maternal diabetes are traditional risk factors for hypocalcemia in infants of diabetic mothers (IDMs). The aim of this study was to determine the relative contribution of these factors separately and combined in a cohort of diabetic pregnancies managed prospectively in the recent 9 years and to find accurate predictors of neonatal hypocalcemia in infants of diabetic mothers. We hypothesized that these factors plus low cord blood calcium (Ca) concentration allow prediction of IDMs who develop neonatal hypocalcemia. We studied 186 IDMs (White class B-RT); gestational age (GA, weeks) was by last menstrual period, confirmed +/- 2 weeks by Ballard score. The goals of glycemic control were: preprandial blood glucose less than 100 mg/dl and 90-minute postprandial blood glucose less than 140 mg/dl. Apgar scores, and cord, 24-, 48- and 72-hour serum calcium (Ca) (mg/dl) and magnesium (Mg; mg/dl) were determined. In univariate analysis, lowest serum Ca correlated with cord blood Ca (r = 0.48, p less than 0.001), GA (r = 0.37, p less than 0.001), and 1-minute Apgar score (r = 0.18, p = 0.09), but did not correlate with cord Mg or with advanced White class. In multiple regression, cord Ca and GA were dominant effects and other variables became insignificant. Lowest Ca (mg/dl) was predicted as follows: lowest Ca = 34.05 - 3.22 (Ca cord) - 0.84 (GA) + 0.10 (GA) (Ca cord). This equation predicts neonatal hypocalcemia (lowest Ca less than 8 mg/dl) with a sensitivity of 72% and a specificity of 75%. Thus, GA and cord Ca allow determination of IDMs at risk for neonatal hypocalcemia.