The literature data are analyzed and the own observation of the newborn boy with intrapericardial teratoma, which was complicated by the development of non-immune hydrops and lung hypoplasia of fetus, is presented.

In the presented observation, an ultrasound of a pregnant woman at 24 weeks of pregnancy revealed a volume formation of the mediastinum of the fetus, which at 25-26 weeks was determined as a lymphangioma. At the 31 weeks of pregnancy, there was a marked increase in tumor with increasing of heart failure of the fetus was noted. In this regard, at the 31 weeks 6 days of pregnancy, an operative birth by caesarean section was performed. From the moment of birth, the child showed signs of non-immune hydrops and cardiovascular failure, and the condition of the child was assessed as severe. Despite intensive care and repeated drainage of the thoracic, abdominal and pericardial cavities, the newborn died. According to a comprehensive post-mortem examination (post-mortem radiological and autopsy studies), a teratoma of the heart was detected, which was complicated by the development of non-immune hydrops fetalis and hypoplasia of the lungs, which in turn were the direct cause of death. The essential point of the post-mortem examination is the performance of post-mortem MRI and CT. This allowed us to determine the exact location and size of the tumor, to diagnose non-immune hydrops fetalis with a quantitative assessment of the volume of free fluid in the serous cavities and the severity of anasarca, as well as the degree of lung hypoplasia. The mature nature of the teratoma and its structural features were established during histological examination of autopsy material.