The purpose of the study was to compare the fetal thymus volumes of 18-24-week pregnant women with In Vitro Fertilization (IVF) and spontaneous pregnant women.

Inclusion Criteria:

• pregnant between 18-24 weeks
• had no complaints
• between the ages of 18-35
• conceived with in vitro fertilization or spontaneously

Exclusion Criteria:

• history of endocrinopathies (including diabetes mellitus, hyperprolactinemia, Cushing's disease, and congenital adrenal hyperplasia), systemic diseases (e.g. asthma), collagen disorder, hypercholesterolemia, sickle cell anemia, or neoplasm,
• those who had a history of coronary artery disease, angina, or myocardial infarction, or a history of hypertension, coronary arteritis, and electrocardiographic changes that suggest any known history of vascular, infectious, or inflammatory disease, maternal autoimmune disease,
• use of any drugs other than those used for IVF (e.g. insulin sensitizing drugs, oral contraceptives, antiandrogens, statins, aspirin, and corticosteroids) in the 3 months before the pregnancy,
• multiple pregnancy,
• present cigarette and alcohol use,
• abnormal renal, hepatic, and thyroid function test results;
• refusing to participate in the study,
• abnormal fetal findings (fetal anomaly, increased nape transparency, first-second trimester screening test disorder),
• cases who did not meet the criteria for pregnancy after the first tube treatment (ICSI-ET) because of normoresponder, unexplained infertility, or male factor

The study group consisted of normal pregnant women who applied to the pregnancy clinic for routine pregnancy follow-ups