Correlation of nuchal translucency and thyroxine at 11-13 weeks of gestation

Objective: Nuchal translucency (NT) thickness is one of the major screening markers during the first trimester that could be influenced by several factors. Here, we investigated the association between NT thickness and thyroid related hormones. Methods: NT thickness was measured with transabdominal ultrasound in 643 pregnant women between 11 and 13 weeks of gestation. Maternal thyroxine (T4), free thyroxine (fT4) and thyroid-stimulating hormone (TSH) were evaluated. Bivariate correlations were assessed and thyroid profile was subcategorized with regard to the calculated reference ranges. Results: An inverse relation was found between serum levels of maternal T4 with NT thickness (r = -0.128, p = 0.001) and CRL (r = -0.168, p<0.001). TSH and hCG were also found to be correlated (Spearman's correlation coefficient = -0.092, p = 0.019). Prevalence of maternal hypothyroidism and subclinical hypothyroidism were 1.1% and 3.7%, respectively. Conclusion: Thyroid function tests are found to independently influence NT measurements in the first trimester. Assessment of hormones such as thyroxine could optimize the interpretation of screening tests for pathological conditions during pregnancy.