Aim of the study: Trisomy 13 is the third most common autosomal trisomy. The following case report shows an atypical case of trisomy 13, highlighting the usefulness of 3D volume storage and reconstruction, and the necessity of careful interpretation of the first trimester screening results. Case description: The results of the first trimester screening tests were interpreted as normal, and invasive tests were not recommended. At 21 weeks, a bright spot in the left ventricle was noted, and fetal echocardiography was performed at 33 weeks. The scan showed a massive pericardial effusion and a pericardial tumor located in front of the right ventricle. Conclusions: The final diagnosis, made postnatally, revealed an atypical right-sided diaphragmatic hernia. Part of the liver was displaced to the pericardial cavity, mimicking a pericardial tumor in a baby with trisomy 13. Following the diagnosis of the lethal disorder, the baby was discharged under a home-based palliative care program and died on the 49th day of life.

trisomy 13, pericardial effusion, pericardial tumor, diaphragmatic hernia, fetal echocardiography