Outcome of Pregnancies Diagnosed with TRAP Sequence Prenatally: A Single-Centre Experience

Twin reversed arterial perfusion (TRAP) sequence is a phenomenon seen in 1-3% of monochorionic twin pregnancies, where the acardiac fetus is found to have multiple anomalies. The normal pump twin maintains its own perfusion in addition to that of its acardiac co-twin. As a result, if the acardiac twin increases in size, the burden on the pump twin is increased, leading to cardiac failure, hydrops fetalis, polyhydramnios, premature delivery, and perinatal death. The outcome of pregnancy is largely dependent on the growth of the acardiac twin. In view of high perinatal loss, surgical techniques to interrupt the blood flow to the acardiac twin have been evaluated.

We evaluated interstitial laser therapy, which is the main mode of therapy in our unit, of TRAP pregnancies referred over a 5-year period. Interstitial laser was offered if the blood flow in the acardiac twin was found to be persistent at 2 consecutive examinations or if there were cardiac or hydropic changes in the pump twin at the first examination.

A total of 18 cases of TRAP were referred during this period and all were counselled regarding fetal therapy if the situation were to deteriorate; 5 couples (27.7%) opted for termination of pregnancy; of the remaining 13, 7 (53.8%) agreed to perform intervention following confirmation of a normal karyotype. Six (85.7%) and 1 (14.3%) lasers were performed in the second and third trimesters, respectively; all 7 had a normal outcome of the pump twin. There were 6/13 (46.2%) in the expectant group who continued the pregnancy with no intervention, with 2 term live births (33.3%).

Our study confirms that there is a high risk of spontaneous loss in untreated pregnancies with TRAP, primarily due to polyhydramnios and fetal hydrops. In the pregnancies that underwent interstitial laser, there was a more favourable outcome. Interstitial laser is minimally invasive, safe, and feasible in experienced hands.