RESUMO
OBJECTIVE: To report a case of a large fetal pelvic mass diagnosed at 35 weeks' gestation. DESIGN: Report of a unique case of a fetal abdominal mass, emphasizing the wide range of differential diagnoses. Although rare reports of fetal ovarian cysts exist, even fewer describe endometriosis or endometriomas in infants. As of 2014 there have not been any published reports of fetal endometriosis from the United States. SETTING: Large tertiary community hospital. PATIENT(S): An 18-year-old pregnant woman diagnosed with a large fetal pelvic mass at 35 weeks' gestation. INTERVENTION(S): Diagnosis of a fetal abdominal mass at 35 weeks with documented enlargement at 37 weeks leading to delivery, with subsequent removal of the mass on day of life 2. MAIN OUTCOME MEASURE(S): On day of life 2, a pediatric surgeon performed an exploratory laparotomy and left salpingo-oophorectomy. RESULT(S): Final pathology showed a 7.0 × 4.5 cm cyst-like structure consistent with hemorrhagic ovarian cyst wall and focal endometriosis. CONCLUSION(S): It can be very difficult to counsel patients regarding an abdominal mass in their unborn child. These difficulties stem from the large list of differential diagnoses and the range of prognoses they portend. As more and more of these cases appear in the literature, we are able to gain a better understanding of how each of these diagnoses present and appear on imaging, allowing us to provide a more accurate diagnosis and counseling antenatally.