Thyroid dysfunction during pregnancy is relatively common and can cause obstetric complications and significantly influence fetal development.
We aimed to evaluate postnatal clinical and laboratory characteristics in the first days of life in infants born to mothers with a thyroid disorder.
We conducted a retrospective single-center study with neonates born between January 2010 and May 2020. Early laboratory parameters and clinical findings in neonates of mothers with different maternal thyroid disorders were analysed.
We included 314 newborns of mothers with Hashimoto’s thyroiditis, 171 with non-Hashimoto’s hypothyroidism, 42 with Graves’ disease, 12 with non-Graves’ hyperthyroidism, and 190 neonates born to mothers without thyroid dysfunction. No demographic, clinical, and laboratory differences were observed between neonates from mothers with a thyroid disorder and healthy mothers. FT3 and fT4 correlated positively with gestational age (p < 0.001; p < 0.001) and negatively with maximum postnatal weight loss (p = 0.043; p < 0.001). High fT3 values were associated with lower maximum bilirubin levels (p = 0.020).
Despite an increased morbidity risk due to the transplacental exposure to maternal antibodies, most neonates born to mothers with thyroid disorders show normal postnatal development and thyroid function tests during the first days of life.

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