The article presents the results of monitoring the course and development of a benign tumor in the fetus - lymphangiomy, which is a rare pathology (up to 10% of benign neoplasms in children). These neoplasms are not caused by chromosomal abnormalities and, as a rule, are characterized by a favorable intrauterine and postnatal course, which depends on the size and location of the formation. The article describes a benign tumor of the lymphatic system of a congenital nature in the neck, presents the results of monitoring the course and development of the tumor in the fetus. The results of the study are based on general clinical data and ultrasound data. With antenatal diagnosis of large lymphangioma in the neck, operative delivery is indicated. Purpose - to present a clinical case of prenatal diagnosis of lymphangioma in the fetus, to describe the features of observation and clinical case history. Materials and methods. This clinical case is presented in a patient V., 31 years old, who had a second delivery, third pregnancy. Data from general clinical studies, ultrasound examination (ultrasound scanner Aloka 3500) were used. Results. According to the results of general clinical examinations, the patient's tests during pregnancy were within the normal range. According to the biochemical screening data of the first trimester, the pregnant woman is classified as a low-risk group. An ultrasound examination of the III trimester, at 32 weeks, revealed a mass in the axillary region of the fetus on the right (lymphangioma). Early diagnosis of fetal lymphangioma allows you to control the course of pregnancy, childbirth, and evaluate possible complications. Conclusions. The described clinical case of lymphangioma is an illustration of dynamic prenatal and postnatal observation and its ultrasonic interpretation. Early diagnosis of benign tumors of the lymphatic system of a congenital nature allows you to adequately control the course of pregnancy, childbirth, assess placental insufficiency and anticipate complications. The research was carried out in accordance with the principles of the Helsinki Declaration. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.