Outcomes in Pregnant Patients with Subclinical Hypothyroidism and Thyroid Autoimmunity: A Critical Appraisal of Recent Randomized Controlled Trials

The management of subclinical hypothyroidism (SCH) and thyroid autoimmunity (TAI) in pregnancy is still uncertain. Over the years, several scientific societies published guidelines on the management of thyroid dysfunction before, during, and after pregnancy, the most recent ones being published by the American Thyroid Association (ATA) in 2017. This study aimed to review the published literature in the field from 2017 onward to investigate whether new findings can change ATA recommendations. A literature search was conducted in PubMed between March 2017 (date of the publication of the ATA guidelines) and March 2020. The research was restricted to randomized controlled trials (RCTs), having pregnancy-related complications in patients with SCH and TAI as the main focus. A total of 5 RCTs were retrieved, 2 of which investigated pregnant women with SCH and 3 with TAI. Selected studies displayed proofs against treating maternal SCH and hypothyroxinemia because no benefit from LT4 was demonstrated in offspring intelligence quotient and in pregnancy outcomes; moreover, they reported proofs against treating TAI patients because no benefit from LT4 was demonstrated in improving pregnancy rate or live birth rate or reducing miscarriage rate.RCTs published from 2017 to 2020 might have a significant impact on current ATA guidelines. In particular, they suggested that isolated hypothyroxinemia and SCH should not be treated and that considering treatment in antibodypositive women, especially those with TSH of 2.5–4.0 mIU/L, would not be justified; they suggested that infertility and miscarriage rates are not decreased by LT4 treatment in euthyroid antibody-positive women seeking pregnancy.