P36.09: A rare case of late second trimester presentation of bilateral ovarian abscess causing ileus in twin pregnancy after oocyte retrieval for IVF

Abstract

Acephalus acardiac fetus is a rare condition due to twin reverse arterial perfusion syndrome (TRAP-sequence), affecting 1/35000 pregnancies and about 1% of monochorionic twins. In this condition the donor fetus (pump fetus) provides circulation for itself and the recipient twin, developing progressive heart failure. The acardiac twin is grossly abnormal, with severe reduction anomalies of the upper part of the body. We report a case of an acephalus acardiac fetus presenting at the third trimester scan as a small complex cystic mass. A 34-year-old woman, gravida 1, with a singleton pregnancy, was referred to our unit at 31 weeks and 6 days of gestation for a detailed scan, because of a neck/thorax fetal mass. The scan revealed an IUGR fetus (abdominal circumference at 10th centile) with no evidence of structural anomalies. The umbilical and uterine artery Doppler flow were normal (umbilical artery PI 0.97, 50th centile; RI right uterine artery 0.53; RI left uterine artery 0.45). An intramniotic complex mass, measuring 9 cm × 5 cm, was visualized, independent from fetal structures and from the uterus wall. A little and thin ‘cord-like’ structure connecting the cyst to the placenta was seen. Color and pulsed Doppler showed an umbilical artery flow. The diagnosis of acephalus acardiac twin was therefore suggested. The patient underwent weekly ultrasound examinations. At 35 weeks’ gestation a Cesarean section was performed, because of donor progressive growth restriction, giving birth to a female healthy baby, weighing 2400 g, Apgar 9. Post-mortem examination of the small cystic mass confirmed prenatal diagnosis. Our report demonstrates that TRAP-sequence could present as an intramniotic small complex mass and, regardless of the dimension, affect pump twin growth.