CORRELATES OF LOW THYROXINE VALUES AT NEWBORN SCREENING AMONG INFANTSBORN BEFORE 32 WEEKS GESTATION

We assessed the relation of perinatal factors to severe hypothyroxinem ia of prematurity, defined as thyroxine value more than 2.6 standard d eviations below the mean for newborns. The 365 survivors of birth befo re 32 weeks gestation were enrolled in a population-based study of the correlates of neonatal brain injury. In this historical cohort study, mothers were interviewed; perinatal data were abstracted from medical records and neonatal data were collected prospectively. Neonatal thyr oxine screening values were retrieved from the New Jersey State Depart ment of Health. Associated with severe hypothyroxinemia were: gestatio nal age 23-27 weeks vs. 31 weeks (OR = 5.1, 95% CI 1.7, 15.2), later a ge at thyroxine test (OR = 1.6 per day, 95% CI 1.2, 2.1), fraction ins pired oxygen at age 24 h > 40% (OR = 3.2, 95% CI 1.1, 8.8), mechanical ventilation (OR = 5.1, 95% CI 1.3, 19.4), diastolic blood pressure <2 0 mmHg (OR = 2.3, 95% CI 1.2, 4.3), and > 12 years of maternal educati on (OR = 0.4, 95% CI 0.22, 1.0). Infants with severe hypothyroxinemia bad higher mortality, more days of oxygen supplementation, ventilation and hospitalization and were. 11 times more likely to require oxygen supplementation at the postnatal age equivalent to 36 weeks gestationa l age (odds. ratio 10.6, 95% CI 2.3, 48.8). In preterm infants, neonat al thyroxine levels obtained at newborn screening in the first week of life may convey important prognostic information about mortality, mor bidity, and the risk for bronchopulmonary dysplasia. (C) 1997 Elsevier Science Ireland Ltd.