P17.09: Impact of the delay between fetal death and delivery on the success of postmortem ultrasound following termination of pregnancy

Objectives: To explore the prenatal ultrasonic characteristics of fetus in fetu. Methods: 8 cases of fetus in fetu that confirmed by pathology in our hospital were retrospectively analysed. Results: There were 8 cases of fetus in fetu in this group. 4 cases were located in the retroperitoneum, 2 cases in the sacrococcygeal region, 2 case in the face. The earliest time was 18+2 weeks of the gestation when the mass was first found by prenatal ultrasound. 2 cases were found before labour. The mass can be found by ultrasound at a minimum size of 1.1cm × 1.1cm. The maximum mass was 16cm × 10cm. The ultrasonic imaging shows a solid/cystic mass and the boundary is clear. The surrounding organs were compressed because of the enlarged mass. 4 cases were diagnosed as fetus in fetu by prenatal ultrasound; 2 cases were thought to be teratomas; 2 cases were unclear. 4 cases of retroperitoneal fetus in fetu were recovered by surgery after birth and no recurrence was found till now; the other 4 cases were done induced labour. Pathology showed that the most common component in parasites was calcification (90%). Different organs can be seen in fetus in fetu, including vertebral column, long bones, limb buds, skin and the vessels. The prenatal ultrasound showed 100% of calcification compared with pathology, and showed 85.7% of vertebral column, 83.3% of axial skeleton, 71.4% of skin and vessels. Prenatal ultrasound did not detect some organs including hairs in 6 cases, intestinal tracts in 5 cases, kidney in 1 case and combined malformations including umbilical bulge in 2 cases, anencephalus in 2 cases, spina bifida in 1 case. One smaller parasite of twin fetus in fetu was missed in prenatal ultrasound. Conclusions: The ultrasonic imaging of fetus in fetu is characteristic and the systemic prenatal ultrasound has a very important role in diagnosis of fetus in fetu.