Comparison of fetal cardiac structure in hypothyroid pregnant women receiving thyroid hormone replacement therapy and healthy controls

Objective: Thyroid hormone is required for normal fetal brain development, neuronal proliferation, migration and structural organization. We aimed to investigate fetal cardiac structure in fetuses of hypothyroid pregnant women receiving thyroid hormone replacement therapy and to compare it with normal pregnancies, including fetal outcome and delivery results. Methods: Singleton pregnant women whose ages were between 18–45 years and weeks of gestation were between 26–34 were included in the study. Their routine laboratory test reports, ultrasonographic measurements (fetal echo) and postnatal follow-up data were recorded. Patients were grouped according to the presence of diagnosis of hypothyroidism. The patients with hypothyroidism during pregnancy were included in Group 1 while healthy pregnancies with similar features were considered as controls and included in Group 2. All women with hypothyroidism were taking thyroid hormone replacement. All ultrasonographic and laboratory data measurements were collected from the system files and were compared between groups. Results: A total of 89 patients (41 hypothyroidism and 48 controls) were recruited to the study. Serum TSH levels of patients with hypothyroidism (Group 1) was significantly higher than the controls. In fetal cardiac examination, left ventricular (LV) and right ventricular (RV) wall thicknesses, and interventricular septum thicknesses at the end of systole and diastole were not statistically significant in both groups. Apgar scores, fetal gender and mean fetal birth weight were all similar between the groups. Conclusion: There is no myocardial structural difference in fetuses of pregnant women who were diagnosed with hypothyroidism and received thyroid hormone replacement therapy compared to healthy controls. Thyroid replacement therapy in hypothyroid mothers might affect and treat fetal cardiac abnormalities.