Association between Thyroid Hormones and the Risk Level of Screening Tests in the First Trimester of Pregnancy in Hypothyroid Women

Background: Endocrine disorders, such as hypothyroidism, can impact fetal growth and development. The significance and necessity of fetal screening before birth are critical for the prevention of congenital disabilities. The present study aimed to evaluate the association between thyroid hormones, specifically T3, T4, FT3, FT4, TSH, Anti TPO, Free BhCG, B-MOM, P-MOM, and NT-MOM, and the risk of screening tests conducted during the first trimester of pregnancy in women diagnosed with hypothyroidism.Methods: This retrospective, case-control study included 82 pregnant women in their first trimester who were referred for fetal screening tests between 2022 and 2023 at Imam Reza and Motazadi hospitals in Kermanshah, Iran. The case group consisted of 41 pregnant women diagnosed with hypothyroidism and treated with levothyroxine, and the control group comprised 41 pregnant women with normal thyroid function. The assessment of serum levels of T3, free T3, T4, free T4, TSH, and Anti TPO was carried out using the ELISA method, while the first-stage fetal screening tests, including Free BhCG, B-MOM, P-MOM, and NT-MOM, were conducted using the Electro-chemiluminescent (ECL) method. Subsequently, data analysis was conducted using SPSS.Results: In the case group, the average levels of TSH (P=0.001), TPO (P=0.006), trisomy 21 (P=0.001), and trisomy 13/18 (P=0.001) were significantly higher as compared with the control group. Conversely, in the case group, PAPP-A was significantly lower (P=0.001). However, there was no statistically significant difference between the two groups in terms of mean levels of beta-hCG (P=0.297), B-MoM (P=0.202), and NT-MoM (P=0.221). Furthermore, in the case group treated with levothyroxine, mean serum TSH level was significantly higher in the screen positive and medium risk groups of Down syndrome (DS) as compared with the negative screen group (P=0.014).Conclusion: Our results indicated that it is important to promptly identify pregnant women with hypothyroidism and ensure that timely screening tests for fetal health are carried out as a mandatory practice.