Maternal Thyroid Function in the First Twenty Weeks of Pregnancy and Subsequent Fetal and Infant Development: A Prospective Population-Based Cohort Study in China

Context: There are a few prospective population-based cohort studies evaluating the effects of maternal thyroid dysfunctions on fetal and infant developments, but they are inconsistent. Objective: The objective of the study was to investigate the effects of maternal thyroid dysfunction on fetal and infant development. Setting and Participants: The study was nested within a prospective population-based China-Anhui Birth Defects and Child Development study. A total of 1017 women with singleton pregnancies participated in this study. Maternal serum samples in the first 20 wk of pregnancy were tested for thyroid hormones (TSH and free T4). Pregnant women were classified by hormone status into percentile categories based on laboratory assay and were compared accordingly. Main Outcomes: Outcomes included fetal loss, malformation, birth weight, preterm delivery, fetal stress, neonatal death, and infant development. Results: Clinical hypothyroidism was associated with increased fetal loss, low birth weight, and congenital circulation system malformations; the adjusted odds ratios [95% confidence interval (CI)] were 13.45 (2.54–71.20), 9.05 (1.01–80.90), and 10.44 (1.15–94.62), respectively. Subclinical hypothyroidism was associated with increased fetal distress, preterm delivery, poor vision development, and neurodevelopmental delay; the adjusted odds ratios (95% CI) were 3.65 (1.44–9.26), 3.32 (1.22–9.05), 5.34 (1.09–26.16), and 10.49 (1.01–119.19), respectively. Isolated hypothyroxinemia was related to fetal distress, small for gestational age, and musculoskeletal malformations; the adjusted odds ratios (95% CI) were 2.95 (1.08–8.05), 3.55 (1.01–12.83), and 9.12 (1.67–49.70), respectively. Isolated hyperthyroxinemia was associated with spontaneous abortion; the adjusted odds ratio (95% CI) was 6.02 (1.25–28.96). Clinical hyperthyroidism was associated with hearing dysplasia; the adjusted odds ratio (95% CI) was 12.14 (1.22–120.70). Conclusions: Thyroid dysfunction in the first 20 wk of pregnancy may result in fetal loss and dysplasia and some congenital malformations.