Neonatal effects of maternal hypothyroxinemia during early pregnancy

OBJECTIVE. We sought to examine the neurobehavioral profile of neonates who are born to women with hypothyroxinemia during early pregnancy. METHODS. Examined were 108 neonates who were born to mothers with low maternal free thyroid hormone (fT4 concentrations; < 10th percentile) at 12 weeks' gestation (case patients) and 96 neonates who were born to women whose fT4 values were between the 50th and 90th percentiles, matched for parity and gravidity (control subjects). Newborn development was assessed at 3 weeks of age using the Neonatal Behavioral Assessment Scale. Maternal thyroid function (fT4 and thyrotropin hormone) was assessed at 12, 24, and 32 weeks' gestation. RESULTS. Infants of women with hypothyroxinemia at 12 weeks' gestation had significantly lower scores on the Neonatal Behavioral Assessment Scale orientation index compared with subjects. Regression analysis showed that first-trimester maternal fT4 but not maternal TSH or fT4 later in gestation was a significant predictor of orientation scores. CONCLUSIONS. This study confirms that maternal hypothyroxinemia constitutes a serious risk factor for neurodevelopmental difficulties that can be identified in neonates as young as 3 weeks of age.