Study of the Factors Leading to Fetal and Neonatal Dysthyroidism in Children of Patients With Graves Disease.

Context: Neonatal hyperthyroidism was first described in 1912 and in 1964 was shown to be linked to transplacental passage of maternal antibodies. Few multicenter studies have described the perinatal factors leading to fetal and neonatal dysthyroidism.

Objective: To show how fetal dysthyroidism (FD) and neonatal dysthyroidism (ND) can be predicted from perinatal variables, in particular, the levels of anti-thyrotropin receptor antibodies (TRAbs) circulating in the mother and child.

Design and Patients: This was a retrospective multicenter study of data from the medical records of all patients monitored for pregnancy from 2007 to 2014.

Setting: Among 280,000 births, the medical records of 2288 women with thyroid dysfunction were selected and screened, and 417 women with Graves disease and positive for TRAbs during pregnancy were included.

Results: Using the maternal TRAb levels, the cutoff value of 2.5 IU/L best predicted for FD, with a sensitivity of 100% and specificity of 64%. Using the newborn TRAb levels, the cutoff value of 6.8 IU/L best predicted for ND, with a sensitivity of 100% and a specificity of 94%. In our study, 65% of women with a history of Graves disease did not receive antithyroid drugs during pregnancy but still had infants at risk of ND.

Conclusions: In pregnant women with TRAb levels ≥2.5 IU/L, fetal ultrasound monitoring is essential until delivery. All newborns with TRAb levels ≥6.8 IU/L should be examined by a pediatrician with special attention for thyroid dysfunction and treated, if necessary.