The Impact of Chronic Autoimmune Thyroiditis During Pregnancy on Maternal and Fetal Outcomes

Background/Objectives: Thyroid dysfunction during pregnancy is associated with a range of adverse perinatal outcomes. This study aims to evaluate the effect of maternal thyroid autoimmunity on selected gestational and perinatal outcomes of the newborn in a region with adequate iodine intake. Methods: This retrospective study included 74 full-term singleton pregnancies from women living in the coastal region of Romania. Participants were divided into two groups: group 1—women with chronic autoimmune thyroiditis and euthyroidism; group 2—women without thyroid disorders, serving as the control group. Maternal variables assessed included serum thyroid hormone levels and antithyroid autoantibodies. For newborns, parameters such as birth weight, neonatal TSH levels, and the incidence of gestational and perinatal events were evaluated. Results: The incidence of chronic autoimmune thyroiditis in the study population was 36.4%. Maternal thyroid autoimmunity was associated with an increased incidence of low birth weight, observed in 11% of the autoimmune group compared with 2.1% in the control group (p = 0.099). The incidence of preterm birth was significantly higher in the autoimmune group (18.5% vs. 4.2% in controls, p = 0.043), corresponding to a 4.3-fold increase in relative risk. The most frequent perinatal complication observed in pregnant women with thyroid autoimmunity was spontaneous abortion (11.1%). The median urinary iodine concentrations were within the adequate range in both study groups. Conclusions: Thyroid autoimmunity during pregnancy presents significant clinical challenges, even in areas with adequate iodine intake. Maternal autoimmune thyroiditis constitutes an established risk factor for impaired fetal development and adverse perinatal outcomes. Early assessment of thyroid function prior to conception or during the first trimester is recommended for both diagnostic and preventive purposes.