Effect of maternal thyroid dysfunction on obstetric and perinatal outcomes
Lee, Sun Young
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INTRODUCTION: The effects of maternal subclinical hypothyroidism on pregnancy outcomes are not clear. We performed a cohort study to assess potential associations between maternal thyrotropin (TSH) levels in pregnancy and obstetric and perinatal outcomes. METHODS: Women aged ≥18 years with a singleton gestation seen for prenatal care at Boston Medical Center from 1/1/2007 through 5/22/2014 and their fetuses and infants were included. Women with known thyroid disease or use of thyroid medication or lithium were excluded. Maternal demographics, pertinent medical and obstetric histories, and initial serum TSH levels during pregnancy were assessed in relation to adverse obstetric and perinatal outcomes. Normal TSH values were defined as ≤4mIU/L, low birth weight (LBW) as ≤2500g, and prematurity as gestational age (GA) at birth <37weeks. RESULTS: A total of 8,413 pregnant women (mean age 29.1years, 15% white, 60% black, 13% Hispanic) and their fetuses and infants (mean GA at birth 38.5wks, 52% male, mean birth weight 3.2kg) were included in the analyses. The median (range) TSH level was 1.06 (<0.01–106.41) mIU/L, and 130 women (1.6%) had TSH >4mIU/L. Maternal TSH levels >4mIU/L were associated with increased risks of prematurity (risk ratio (RR) 2.15; 95% confidence interval (CI) 1.14–4.03) and neonatal respiratory distress syndrome (RDS) (RR 2.80; 95% CI 1.01, 7.78) compared to maternal TSH levels ≤4mIU/L. Although not statistically significant, there were increased risks of fetal loss, preeclampsia/eclampsia, and low birth weight associated with TSH levels >4mIU/L (RR 1.54, 95% CI 0.61–3.90; RR 1.45, 95% CI 0.70–2.99; and RR 2.16, 95% CI 0.76–6.13, respectively). TSH levels >4mIU/L were not associated with preterm labor, placental abruption, cesarean section, gestational hypertension, gestational diabetes, or neonatal intensive care unit admission CONCLUSION: Maternal serum TSH concentration >4mIU/L in pregnancy was associated with approximately 2-fold increased risks of prematurity and RDS in offspring. Elevated TSH was also associated with unstable increases in the risk of fetal loss, preeclampsia/eclampsia, and low birth weight. However, more interventional studies are needed to ascertain the benefit of treatment of maternal subclinical hypothyroidism in pregnancy.
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