EP20.12: The heartless triplet: acardius anceps complicating monochorionic pregnancy

Abstract

Twin Reversed Arterial Perfusion (TRAP) sequence affects 1% of monochorionic twins and 3% of monochorionic triplets. Acardius acephalus, acardius amorphous, acardius acormus and acardius anceps have been described. In the acardius anceps (9% of cases) the fetal head and body are differentiated. A 28 y.o. woman, G1P0 was referred at 14 weeks gestation with a monochorionic triamniotic triplet pregnancy complicated by demise of triplet 3; the fetus appeared fully formed with a marked cystic hygroma and no heartbeat. At 18 weeks there was a significant increase in size, hydrops and Doppler perfusion into triplet 3; TRAP sequence was diagnosed. End-diastolic flow (EDF) in the umbilical artery and a-wave in the ductus venosus of triplet 2 were absent, therefore interstitial laser coagulation of pelvic vessels was performed in triplet 3. Subsequent positive EDF in umbilical artery of triplet 2 deteriorated at 33+2 weeks, the babies were therefore delivered by emergency Caesarean section. Triplet 1 weight was 2030g with Apgars 10,10 and Triplet 2: 1650g with Apgars 7,9,10. Acardius anceps variant of TRAP was diagnosed on autopsy of triplet 3. Unlike other cases described, the upper body was better developed with normal occipital, parietal and frontal bones. Aortic type vessel was extending rostrally with two apparent brachial arteries and two apparent common carotid-like arteries. The upper limbs had 5 digits on each hand and were held in partially reducible flexion at shoulders and elbows; there was a bilateral cleft palate. In the lower body, the vasculature was difficult to assess, fracture dislocations were seen at knees and ankles, with fusion of the fourth and fifth digits of the feet. QFPCR confirmed a monozygotic pregnancy. The above case highlights the difficulties posed by well differentiated variants of TRAP at early gestations and the importance of a thorough examination, including Doppler studies to aid the diagnosis of these rare and challenging cases.