An analysis of real-life data of infants born to mothers with autoimmune thyroiditis: do they need to be followed-up?

Background: Infants born to mothers with autoimmune thyroiditis (AT) could be at risk of developing thyroid dysfunction, and maternal anti-thyroid antibodies have been shown to have a clinical impact on offspring. We aimed at evaluating the usefulness of our follow-up intervention protocol in newborns from mothers with AT and to define the most appropriate management for these neonates. Methods: 89 mothers with AT and their newborns were included. Data on maternal thyroid function and autoimmunity were collected; serum thyroid function and autoimmunity of infants were assessed regularly until normalisation of thyroid stimulating hormone (TSH) and anti-thyroid antibodies, according to the local protocol. Results: Thyroid auto-antibodies were measured in 38% and in 62% of mothers before and during pregnancy, respectively. Anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-TG) were positive in 97% and 61%, respectively, of the mothers assessed. Anti-TSH receptor antibodies (TRAb) were checked in 18% of the mothers and all were negative. 94% of newborns at first evaluation had positive anti-thyroid antibodies, starting to normalise or decrease from the second month of life. Analysing TSH levels according to the days of postnatal life of collection samples (T1: 30 ± 7 days, T2: 61 ± 9 days, T3: 105 ± 49 days, T4: 135 ± 31 days, T5: 247 ± 64 days), peak TSH levels were found at T4 (4.4 ± 2.2 mU/L), within the cut-off of 6 mU/L. 84% of children maintained a normal thyroid function during follow-up; 12% of infants presented a TSH above 6 mU/L at least in one blood test, showing normalisation during follow-up. Only one infant received replacement therapy for hypothyroidism at 2 months. 91% of the 22 thyroid ultrasounds (US) performed were normal. In those with changes thyroid function normalised anyway. Conclusions: Mothers with AT do not seem to deliver newborns at risk of overt hypothyroidism. However, because of the possible negative effects of maternal anti-thyroid antibodies, we underline the importance of monitoring thyroid autoimmunity during pregnancy, including both anti-TG besides anti-TPO antibodies.