Department of Gynecology, Félix Guyon'Hospital, 97400 Saint-Denis, Réunion, France.

A 24-year-old primigravidaria patient was referred to our antenatal unit at 35 weeks for further evaluation of a fetal abdominal mass. Ultrasound examination at 12 weeks (nuchal translucency = 1 mm) and at 24 weeks revealed no abnormality. 

At 35 weeks, the last ultrasound scan revealed appropriate-for-gestational age growth indices but an abdominal mass. The mass was approximately 40 mm X 34 mm X 38 mm in diameter. The cyst appeared to be well-demarcated and hyperechoic in the center (Figure 1, 2). A third-level ultrasound revealed a large, nonvascular, multilocular right-side cystic mass. 

At 36 weeks, the mass was located in the right inferior quadrant of the abdomen. There was no polyhydramnios or hydrops. The sex was female. Kidneys were normal (Figure 3, 4, 5, 6). 

The couple was referred to genetic counseling to discuss additional testing options. Amniocentesis was not performed. The diagnosis was right ovary cyst. The patient delivered spontaneously at 40 weeks, with a normal postnatal adaptation. At day 4, a postnatal ultrasound confirmed the diagnosis. Surgery was necessary with right ovariectomy for necrosis. The uterus and left ovary were normal. The patient and her baby were discharged later.

Figure 1, 2:  Transverse view of the fetal abdomen at 35 weeks shows a multicystic mass in the right inferior quadrant.