RESUMO
Background: Thyroid hormones play an important role in fetal neural and cognitive development. Therefore thyroid abnormalities should be detected and treated early during pregnancy. Aim: To assess the frequency and risk factors for functional thyroid disorders during the first trimester of pregnancy. Material and Methods: A blood sample was obtained from women during their first trimester of pregnancy, consulting in a prenatal care facility. Women with known thyroid diseases were excluded from the study. Thyroid stimulating hormone (TSH), total thyroxine (T4) and free thyroxine (fT4) were measured by electrochemoluminiscence. Antithyroid peroxidase antibodies (anti TPO) were measured by enzyme immunoassay. Results: Five hundred and ten women aged 25.7 ± 6.6 years were assessed. The frequency of clinical hypothyroidism was 0.6%, subclinical hypothyroidism 35.3% and clinical hyperthyroidism 1%. Five percent of women with hypothyroidism and 3.5% of euthyroid women had positive anti TPO antibodies. There was no association between the frequency of thyroid diseases and risk factors for thyroid diseases. Conclusions: There is a high frequency of subclinical thyroid diseases among women consulting in this prenatal care clinic.