Intra-abdominal fetus in fetu presenting at 31 weeks gestational age.

Fetus in fetu (FIF) is a rare anomaly of diamniotic monochorionic twins, in which a malformed fetus resides in its twin's body. This report shows a case with the prenatal diagnosis of FIF at Tu Du hospital. A 23-year-old woman, first-time pregnant, presented at the hospital with an abdominal mass in the fetus at 31 weeks and 4 days of gestation. The ultrasound showed an abnormal mass with the images of calcified features located in the left hypochondriac region and the kidney's upper pole. These images had shapes of skull, femur, spine and became more apparent as the fetus grew. Then, the patient was monitored and delivered at our hospital. The infant was moved to the Children's Hospital 1 and diagnosed with FIF by ultrasound. The surgical resection was performed at 12 days of birth.