[Maternal autoimmune thyroid disease: relevance for the newborn]. / Enfermedad tiroidea autoinmunitaria materna: repercusión en el recién nacido.

BACKGROUND AND OBJECTIVE: Autoimmune thyroid disease is amongst the most frequent endocrine disorders during pregnancy. It is associated with an increase in perinatal morbidity, congenital defects, neurological damage, fetal and neonatal thyroid dysfunction. Maternal thyroid hormones play a key role in child neurodevelopment. We aimed to evaluate the thyroid function and the clinical course of neonates born from mothers with autoimmune thyroid disease during the first months of life in order to define the follow-up. PATIENTS AND METHOD: We monitored thyroid function and clinical status during the first months in 81 newborns of mothers with autoimmune thyroid disease; 16 had Graves disease and 65 autoimmune thyroiditis. RESULTS: A percentage of 4.93 newborns had congenital defects, and 8.64% neonates showed an increase in thyrotropin (TSH) (>9.5 µUI/mL 2 times) and required thyroxin within the first month of life. A 85.7% of these showed a negative newborn screening (due to a later increase of TSH). A higher TSH value in the newborn was related to an older age of the mother, higher levels of thyroid peroxidase (TPO) antibody during pregnancy and lower birth weight. A higher free thyroxine (FT4) value in the newborn was related to fewer days of life and mothers with Graves disease. CONCLUSIONS: We recommend the evaluation of TSH, T4 and TPO antibodies before 10 weeks in all pregnant women with follow-up if maternal thyroid autoimmunity or disorders is detected. It is also recommended to test children's serum TSH and FT4 at 48 h of life in newborns of mothers with autoimmune thyroid disease and repeat them between the 2nd and 4th week in children with TSH>6 µUI/mL. Careful endocrine follow-up is advised in pregnant women and children if hyperthyroidism is detected.