ObjectiveAdverse maternal outcomes and perinatal complications are closely associated with overt maternal hypothyroidism, but whether these complications occur in women with subclinical hypothyroidism (SCH) during pregnancy remains controversial. The aim of this study was to evaluate the effects of SCH on maternal and perinatal outcomes during pregnancy.MethodsA prospective study of data from 8012 pregnant women (371 women with SCH, 7641 euthyroid women) was performed. Maternal serum samples were collected in different trimesters to examine thyroid hormone concentrations. SCH was defined as a thyroid stimulating hormone concentration exceeding the trimester-specific reference value with a normal free thyroxine concentration. The occurrence of maternal outcomes, including gestational hypertension (GH), gestational diabetes mellitus, placenta previa, placental abruption, prelabor rupture of membranes (PROM), and premature delivery; and perinatal outcomes, including intrauterine growth restriction (IUGR), fetal distress, low birth weight (LBW; live birth weight ≤2500 g), stillbirth, and malformation, was recorded. Logistic regression with adjustment for confounding demographic and medical factors was used to determine the risks of adverse outcomes in patients with SCH.ResultsCompared with euthyroid status, SCH was associated with higher rates of GH (1.819% vs. 3.504%, P = 0.020; χ 2 = 7.345; odds ratio (OR), 2.243; 95% confidence interval (CI), 1.251–4.024), PROM (4.973% vs. 8.625%, P = 0.002; χ 2 = 72.102; adjusted OR, 6.014; 95% CI, 3.975–9.099), IUGR (1.008% vs. 2.965%, <0.001; χ 2 = 13.272; adjusted OR, 3.336; 95% CI, 1.745–6.377), and LBW (1.885% vs. 4.582%, P<0.001; χ 2 = 13.558; adjusted OR, 2.919; 95% CI, 1.650–5.163).ConclusionsThe results of this study indicate that pregnant women with SCH had increased risks of GH and PROM, and their fetuses and infants had increased risks of IUGR and LBW. Thus, routine maternal thyroid function testing is necessary to improve maternal and perinatal outcomes.

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BackgroundThyroid dysfunction during pregnancy is associated with multiple adverse outcomes, but whether all women should be screened for thyroid disorders during pregnancy remains controversial.ObjectiveTo evaluate the effectiveness of the targeted high risk case-finding approach for identifying women with thyroid dysfunction during the first and second trimesters of pregnancy.MethodsLevels of thyroid stimulating hormone (TSH), free thyroxine (FT4), and thyroid peroxidase antibodies (TPOAb) were measured in 3882 Chinese women during the first and second trimester of pregnancy. All tested women were divided into the high risk or non-high risk groups, based on their history, findings from physical examination, or other clinical features suggestive of a thyroid disorder. Diagnosis of thyroid disorders was made according to the standard trimester-specific reference intervals. The prevalence of thyroid disorders in each group was determined, and the feasibility of a screening approach focusing exclusively on high risk women was evaluated to estimate the ability of finding women with thyroid dysfunction.ResultsThe prevalence of overt hypothyroidism or hyperthyroidism in the high risk group was higher than in the non-high risk group during the first trimester (0.8% vs 0, χ2 = 7.10, p = 0.008; 1.6% vs 0.2%, χ2 = 7.02, p = 0.008, respectively). The prevalence of hypothyroxinemia or TPOAb positivity was significantly higher in the high risk group than in the non-high risk group during the second trimester (1.3% vs 0.5%, χ2 = 4.49, p = 0.034; 11.6% vs 8.4%, χ2 = 6.396, p = 0.011, respectively). The total prevalence of hypothyroidism or hyperthyroidism and the prevalence of subclinical hypothyroidism or hyperthyroidism were not statistically different between the high risk and non-high risk groups, for either the first or second trimester.ConclusionThe high risk screening strategy failed to detect the majority of pregnant women with thyroid disorders. Therefore, we recommend universal screening of sTSH, FT4, and TPOAb during the first trimester and second trimester of pregnancy.