same stage of the classification system, characteristics
including the flow amount and diameter of the
vessel of the communicating flow between the TRAP
and acardiac twin are different. The criteria for surgery
are: (1) abdominal circumference of the acardiac
twin is equal to or greater than that of the
pump twin (i.e. acardiac/pump twin ratio ≥ 1.0;
the measurement is taken at the level of the stomach
including the skin); (2) polyhydramnios
(MVP ≥ 8 cm); (3) critically abnormal Doppler studies
in the pump twin (persistent absent or reversed
diastolic blood flow in the umbilical artery, pulsatile
blood flow in the umbilical vein, and/or reversed
blood flow in the ductus venosus); (4) fetal hydrops
of the pump twin, defined as ≥ 2 fetal compartments
with fluid; and (5) monoamniotic twins
(high risk for cord entanglement) [21]. In a review
paper [24], intrafetal laser was chosen as the best
management for TRAP. But further publications
[21,24,25] showed that fetoscopic guide therapy
is also effective in such cases and many more cases
were studied in those papers compared to the previous
study. The first successful umbilical cord ligation
of a TRAP twin in 1994 using custom-designed
instruments and combined endoscopic and ultrasound
guidance was done by Quintero et al [26].
Recently, Quintero et al [21] analyzed 74 cases of
TRAP in a single institution and suggested that
patients with TRAP sequence who are treated with
umbilical cord occlusion have a more favorable
outcome relative to surgical candidates who do not
undergo surgery, provided that the dividing membrane
is not disrupted. That is because if the dividing
membrane is disrupted, the risk of cord accident
and ruptures of membrane would increase.