A case-control study of hypocalcemia in high-risk neonates: racial, but no seasonal differences

A role for vitamin D in the defense against falling serum calcium (Ca) concentrations following cord clamping has been suggested. Since race and season are known to affect vitamin D status, we theorized that black race and birth in winter are additional risk factors for neonatal hypocalcemia (NHC). We retrospectively studied 13,462 infants born at University Hospital (Cincinnati, OH) between January 1, 1984 and December 31, 1987. Serum Ca was measured at 24 hours of age routinely in infants with low birth weight (less than 2500 g), preterm delivery (less than 2500 g), preterm delivery (less than 37 weeks), neonatal asphyxia, and diabetic mothers. After exclusion of infants of diabetic mothers (to remove maternal diabetes as a major confounder) and infants with major congenital anomalies, 714 infants remained. In multiple regression analysis, low serum Ca values were significantly associated with low gestational age (p less than 0.01), low Apgar score (p less than 0.01), and white race (p less than 0.01) (R2 = 0.457). Season or month of birth was not significant. In pair-matched analysis controlling for factors other than season, season of birth did not affect serum Ca. In pair-matched analysis controlling for factors other than race, white race was once again a risk factor for hypocalcemia. Thus, low gestational age, low Apgar score, and white race, but not black race and delivery in winter, are risk factors for NHC. We speculate that in our climate and with the prevailing diet in pregnancy, vitamin D deficiency does not appear to play a role in NHC.(ABSTRACT TRUNCATED AT 250 WORDS)