THE RELATION OF TRANSIENT HYPOTHYROXINEMIA IN PRETERM INFANTS TO NEUROLOGIC DEVELOPMENT AT 2 YEARS OF AGE

Background. Transient hypothyroxinemia, a common finding in premature infants, is not thought to have long-term sequelae or to require treat ment. We investigated whether hypothyroxinemia in premature infants is a cause of subsequent motor and cognitive abnormalities. Methods. In this historical cohort study, we retrieved blood thyroxine values, obt ained on routine screening in the first week of life, from state scree ning records of children who weighed 2000 g or less at birth, who were born at 33 weeks' gestation or earlier, and who were enrolled in a po pulation-based study of the late sequelae of neonatal brain hemorrhage . We investigated the relation of these values to the odds for disabli ng cerebral palsy among 463 subjects for whom data were available and to the mental-development score on the Bayley Scales of Infant Develop ment or the Stanford-Binet Intelligence Scales for Children at the age of two years in 400 subjects. The effects of severe hypothyroxinemia, defined as a blood thyroxine value more than 2.6 SD below the mean fo r New Jersey newborns, were assessed before and after adjustment for g estational age and potentially confounding variables. Results. In anal yses adjusted for gestational age, infants with severe hypothyroxinemi a had a risk of disabling cerebral palsy that was nearly 11 times that of infants without hypothyroxinemia (odds ratio, 10.8; 95 percent con fidence interval, 3.0 to 39.3) and a mean mental-development score at the age of two that was 15.4 points lower (95 percent confidence inter val, 8.1 to 22.6 points) than the mean score of children with normal n eonatal blood thyroxine concentrations. After adjustment for gestation al age and multiple prenatal, perinatal, and early and late neonatal v ariables, severe hypothyroxinemia was still associated with an increas ed risk of disabling cerebral palsy (odds ratio, 4.4; 95 percent confi dence interval, 1.0 to 18.6) and a reduction of nearly 7 points (95 pe rcent confidence interval, 0.3 to 13.2 points) in the mental-developme nt score. Conclusions. Severe hypothyroxinemia in preterm infants may be an important cause of problems in neurologic and mental development detected at the age of two years. (C) 1996, Massachusetts Medical Soc iety.