Sima Nazarpour - Department of Midwifery, Varamin-Pishva Branch, Islamic Azad University, Tehran, Iran / Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Fahimeh Ramezani Tehrani - Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Fereidoun Azizi - Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Background: Thyroid dysfunctions are frequently observed during pregnancy. The maternal thyroid dysfunction is associated with adverse outcomes such as miscarriage, preterm delivery, preeclampsia, postpartum hemorrhage in mother whereas increased risk of impaired neurological development in fetus. This prospective population based study was conducted among pregnant women in the first trimester of pregnancy to estimate the prevalence of thyroid dysfunctions.Methods: A total number of 2404 pregnant women were selected with population based cluster sampling in Shahid Beheshti University prenatal care centers. Overnight blood samples were collected at the first prenatal visit to measure serum levels of thyroid stimulating hormone (TSH), Thyroxine (T4), T-uptake and thyroid peroxidase antibody (TPOAb). TSH and total T4 were assayed by immunoradiometric and radioimmunoassay method, respectively. T-uptake and TPO-Ab were measured by enzyme linked immunosorbent assay. Women with baseline concentrations of TSH 0.1-4 mIU/L, FT4I 1-4.5 and TPO<50IU/ml were considered euthyroid TPOAb-. Overt hyperthyroidism was defined asTSH levels<0.1mIU/L and FT4I> 4.5. Overt hypothyroidism was defined as TSH> 10mIU/L or TSH levels> 4 mIU/L and FT4I<1. Subclinical hypothyroidism was defined as normal FT4I (1-4.5) despite elevated TSH 4-10mIU/L). Subclinical hyperthyroidism was defined as normalFT4I (1-4.5) despite reduced TSH (TSH<0.1mIU/L). TPOAb > 50IU/ml was considered as TPOAb positivity.Results: The results showed that 78.9% (n=1897) of the participants in this study had normal thyroid function, while 21.1% (n=507) of themhad thyroid dysfunction. Frequencies of overt hyperthyroidism and hypothyroidism were 0.7% (n=18) and 4.5% (n = 108), respectively. In this study11.4% (n=274) of the pregnant women had subclinical hypothyroidism. The prevalence of TPOAb+ were 9.5% (n=229) and 4.5% (n=107) of pregnant women were euthyroid and TPOAb.Conclusion: The present study demonstrated thyroid dysfunctions was common in pregnancy and the prevalence of them was 21.1%. This also emphasized the importance of screening pregnant women for thyroid dysfunction to prevent both maternal and fetal morbidity.

Thyroid, dysfunction, prevalence.