Association between previously unknown connective tissue disease and subclinical hypothyroidism diagnosed during first trimester of pregnancy.

OBJECTIVE: To investigate the presence of autoimmune rheumatic disorders among women with autoimmune thyroid disorders diagnosed during the first trimester of pregnancy and subsequent pregnancy outcomes. DESIGN: Case-control study. SETTING: Tertiary obstetric and gynecologic center. PATIENT(S): Pregnant women in the first trimester of pregnancy. INTERVENTION(S): Clinical, laboratory, ultrasonographic evaluations. MAIN OUTCOME MEASURE(S): Thyroid-stimulating hormone (TSH) level; antibodies against thyroperoxidase, thyroid globulin and TSH receptor detection; screening for rheumatic symptoms and antinuclear antibodies (ANA); uterine artery pulsatility index evaluation; pregnancy complication onset. RESULT(S): Out of 3,450 women enrolled, 106 (3%) were diagnosed with autoimmune thyroid disorders. ANA were present in 18 (16.9%) of 106 cases and 26 (12.6%) of 206 controls. Of the cases, 28 (26.4%) of 106 reported rheumatic symptoms, 5 of these were diagnosed with Sjögren syndrome or with undefined connective tissue disease. Autoimmune thyroid diseases are statistically significantly associated with a higher risk of preeclampsia, fetal growth restriction, and overall pregnancy complications compared with controls, with a higher uterine artery pulsatility index, suggesting a defective placentation in thyroid disorders. The effect of ANA-positivity on moderate/severe adverse pregnancy outcomes was statistically significant among the patients with thyroid disorders (9 of 18 as compared to 8 of 88, odds ratio 9.65; 95% confidence interval, 2.613-7.81). CONCLUSION(S): Connective tissue diseases are frequently associated with autoimmune thyroid disorders diagnosed during the first trimester of pregnancy. Thyroid autoimmunity and ANA positivity independently increased the risk of adverse pregnancy outcomes.