Background: The internal thoracic artery arises from the subclavian artery as the first branch. It travels downward on the inside of the rib cage and then gives off six main branches; mediastinal, thymic, pericardiacophrenic, sternal, perforating and intercostal branches.~In literature, there are so many articles that have been focused on thymus size in pregnancies complicated with diabetes mellitus, fetal growth restriction, preterm rupture of membranes and so on. To the best of our knowledge, there is no paper about fetal ITA whose branch are feeding vessel of thymus and ITA Doppler velocity. The arteries supplying the thymus are branches of the internal thoracic, and inferior thyroid arteries. As far as it has been known, growing of a tissue depends on increased blood flow. Before detecting possible blood-flow changes in fetuses complicated with great obstetrics patologies, the investigators should obtain normal values of ITA Doppler velocity.
The aim of this study is to assess the feasibility of visualizing the internal thoracic artery (ITA), establishing the normogram for ITA pulsatility index (PI), resistance index (RI) and acceleration/ejection time (AT/ET) at 24-32 weeks.