ultrasound diagnosis of fatal anomalies

TWIN REVERSED ARTERIAL PERFUSION
may lead to reverse perfusion in one twin. The
perfused twin receives blood with a lower oxygen
content. The resulting hypoxia is responsible
for aplasia or hypoplasia of the heart, head, and
upper extremities. The twin providing the blood
supply is usually healthy. However, cardiac
failure and hydrops may develop in this twin,
leading to intrauterine fetal death.
Ultrasound findings: A second twin is found in
addition to a normal fetus (the providing or
“pump twin”), in which a heart or a heart beat
cannot be demonstrated. The recipient is usually
hydropic, and has a pulse identical to that of the
“pump twin.” In the affected twin, the head or
brain are usually absent (acranius or anencephaly).
Occasionally, the upper extremities are
also missing. Club feet are frequently detected.
Despite the absence of head and heart, the recipient
fetus demonstrates movements. Signs of
cardiac failure or fetal hydrops may develop in
the “pump twin” (hepatosplenomegaly, pleural
and pericardial effusion, skin edema, cardiomegaly,
enlargement of the right atrium). Hydramnios
is a frequent finding. Oligohydramnios
or anhydramnios is found in the recipient. The
recipient fetus also has a singular umbilical
artery in 50% of cases. Color-coded Doppler imaging
of the umbilical artery near the bladder is the
best method of demonstrating reversed blood
flowin the recipient fetus.
Clinical management: There is a high risk of premature
labor due to hydramnios. Serial scanning
Fig. 15.9 Twin reversed arterial perfusion (TRAP
sequence). The recipient in TRAP sequence at
11+6weeks.Color-coded Doppler scanning demonstrates
the direction of blood flow from the lower
body parts to the thorax and head.
Fig. 15.10 Twin reversed arterial perfusion (TRAP
sequence). The recipient in TRAP sequence at
21+6weeks.Thefetalhead is small and severely
deformed. In this case, in addition to reverse perfusion,
bradycardia was detected in the recipient
(“acranius cardius”).
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