Jianxia Fan1,2,3, Yong Zhang1,2,3, Chen Zhang1, Mirjana Barjaktarovic4, Xi Yang1, Robin P Peeters4, He-Feng Huang1,2,3, Tim I M Korevaar4. 1. International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China. 2. Shanghai Key Laboratory of Embryo Original Diseases, Shanghai, China. 3. Shanghai Municipal Key Clinical Speciality, Shanghai, China. 4. Department of Internal Medicine, Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands.
Abstract
Background: Subclinical thyroid disease occurs in approximately 5-8% of all pregnancies and is associated with a higher risk of adverse outcomes such as miscarriage, preterm birth, and suboptimal child neurodevelopment. It is generally assumed that subclinical thyroid disease that persists from early to late pregnancy is associated with a higher risk of adverse outcomes than transient disease. However, it is unknown as to what percentage of women with subclinical disease during early pregnancy have persistent disease in the third trimester. Methods: This study comprised 42,492 mothers for whom early and late pregnancy thyrotropin (TSH), free thyroxine (fT4), triiodothyronine (T3), or TPOAbs were available and who did not receive thyroid treatment before or during pregnancy. We adjusted for potential confounders, including maternal age, parity, anthropometrics, and β-hCG concentrations. Results: Subclinical hypothyroidism and hypothyroxinemia persisted in 24.8% and 17.7% of cases. Overt hyperthyroidism persisted in 8.4% of cases while subclinical hyperthyroidism persisted in 20.9% of cases. Low T3 persisted in 43.4% of cases while elevated T3 persisted in 15.7% of cases. TPOAb positivity persisted in 84.0% of cases. In women with subclinical hypothyroidism, a TSH below ∼5 mU/L at the time of diagnosis was associated with an up to 50% lower risk of persistency. The fT4 concentration at diagnosis predicted hyperthyroidism persistency and TPOAb positivity predicted persistency of all disease entities. Conclusions: Early pregnancy thyroid disease only persists until the third trimester in 8.4-24.8% of cases when left untreated. The main predictor for persistency is TPOAb positivity, with TPOAb-positive women having a lower risk that subclinical hypothyroidism or hypothyroxinemia persists, but a higher risk that (subclinical) hyperthyroidism persists.
Background: Subclinical thyroid disease occurs in approximately 5-8% of all pregnancies and is associated with a higher risk of adverse outcomes such as miscarriage, preterm birth, and suboptimal child neurodevelopment. It is generally assumed that subclinical thyroid disease that persists from early to late pregnancy is associated with a higher risk of adverse outcomes than transient disease. However, it is unknown as to what percentage of women with subclinical disease during early pregnancy have persistent disease in the third trimester. Methods: This study comprised 42,492 mothers for whom early and late pregnancy thyrotropin (TSH), free thyroxine (fT4), triiodothyronine (T3), or TPOAbs were available and who did not receive thyroid treatment before or during pregnancy. We adjusted for potential confounders, including maternal age, parity, anthropometrics, and β-hCG concentrations. Results: Subclinical hypothyroidism and hypothyroxinemia persisted in 24.8% and 17.7% of cases. Overt hyperthyroidism persisted in 8.4% of cases while subclinical hyperthyroidism persisted in 20.9% of cases. Low T3 persisted in 43.4% of cases while elevated T3 persisted in 15.7% of cases. TPOAb positivity persisted in 84.0% of cases. In women with subclinical hypothyroidism, a TSH below ∼5 mU/L at the time of diagnosis was associated with an up to 50% lower risk of persistency. The fT4 concentration at diagnosis predicted hyperthyroidism persistency and TPOAb positivity predicted persistency of all disease entities. Conclusions: Early pregnancy thyroid disease only persists until the third trimester in 8.4-24.8% of cases when left untreated. The main predictor for persistency is TPOAb positivity, with TPOAb-positive women having a lower risk that subclinical hypothyroidism or hypothyroxinemia persists, but a higher risk that (subclinical) hyperthyroidism persists.