Thyroid Function Testing in Neonates With Maternal History of Disease.

Maternal history of thyroid disease can cause congenital hypothyroidism due to thyroid-stimulatng hormone (TSH) blocking antibodies. No guidelines exist regarding testing beyond the newborn screen. TSH and T4 levels exhibit significant fluctuations after birth which complicates testing. A total of 561 newborns with thyroid function testing done for maternal history of thyroid disease in the newborn nursery were identified retrospectively via chart review, and thyroid disease status was assessed in 352. Newborn screening data were also obtained. Of these infants, 7 had hypothyroidism with 3 having negative newborn screens. No cases of neonatal graves were identified. The 3 infants with negative newborn screens had TSH levels ranging from 6.58 to 28.4 prior to treatment with levothyroxine. All required treatment beyond age 3 years, despite trial off levothyroxine. Infants with maternal history of thyroid disease may require additional testing beyond the newborn screen. However, providers can consider delaying test until after thyroid levels are more stable.