Monochorionic Triplet Pregnancies With Twin Reversed Arterial Perfusion and Acardiac Triplet: Report of Two Cases and Literature Review.

TRAP pregnancies involving monochorionic triplets are extremely rare, calculated to be 1 in 4.5 million. We report two cases of monochorionic triplet pregnancies with an acardiac triplet. In one case, the mother was a 33-year-old G2P1 who underwent dilation and evacuation at 20 weeks due to poor prognosis. The other case involved a 21-year-old G1P0 mother presenting in advanced preterm labor at 21 weeks who elected expectant management. Seventeen cases of monochorionic triplets with TRAP were identified in the literature. Invasive intervention was performed in 10 cases; 9 cases resulted in the survival of the nonacardiac twins and 1 case resulted in the survival of 1 fetus. Our two cases had common sonographic features which included polyhydramnios of all fetuses. Placental features shared between both cases included being large for gestational age and velamentous insertion of the acardiac twin. The acardiac twins in both of our cases were hydropic and demonstrated developed pelvis and lower extremities. One had an omphalocele. Most case reports in the literature review demonstrate similar findings. Two cases of monochorionic triplets with TRAP and acardiac twin are herein described. Successful treatment by invasive interventions have been described in this condition, highlighting the importance of early diagnosis.