ultrasound diagnosis of fatal anomalies

TWIN-TO-TWIN TRANSFUSION SYNDROME
Schwarzler P, Ville Y, Moscosco G, Tennstedt C,
Bollmann R, Chaoui R. Diagnosis of twin reversed
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sequence: successful management with intrafetal alcohol
ablation of acardiac twin and amniodrainage.
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Twin-to-Twin Transfusion Syndrome (TTTS)
Definition: This syndrome is unique to monochorionic
twin pregnancies, and represents an
unbalanced arteriovenous placental shunt leading
to vascular compromise of the fetuses. The
donor gives blood to the recipient twin, resulting
in growth restriction of the donor and volume
overload of the recipient. The recipient twin may
consequently develop cardiac failure. There is a
high rate of intrauterine death of both twins.
Incidence: This occurs in 5–10% of all twin pregnancies.
About 5% of monochorionic pregnancies
are severely affected.
Associated symptoms: “Donor”: anemia, growth
restriction, oligohydramnios, or anhydramnios
(“stuck twin”). “Recipient”: macrosomia, hydramnios,
cardiac failure, fetal hydrops, postnatal
plethora.
Ultrasound findings: Monochorionic, diamniotic
twin pregnancies showing severe disparity in
fetal growth. The fetuses are always of the same
gender (monozygotic). The larger, “recipient”
twin may develop signs of cardiac insufficiency
and hydrops (pleural effusion, pericardial effusion,
ascites, skin edema, hepatosplenomegaly)
as well as hydramnios. Oligohydramnios or even
anhydramnios (“stuck twin”) is the case in
“donor” twin. There is disparity in the circumference
of the umbilical cord. Marginal or velamentous
insertion is frequently seen in the donor
twin. To detect whether there is significant
blood transfusion between the twins, the donor
is given a muscle relaxant (pancuronium)
through its umbilical vein; if there is TTTS, relaxation
of the recipient twin will also occur.
However, vascular anastomoses are found in
over 85% of monochorionic placentas, so that relaxation
of the recipient twin does not necessarily
indicate clinically significant transfusion
due to vascular shunts. The placenta, especially
of the recipient twin, may be thick and swollen.
Fetal echocardiography frequently shows incompetence
of the AV valve in the recipient, due
to volume overload. Rare cases have been reported
in which there is a reversal in the role of
the donor and recipient twins during the progress
of the pregnancy.
Clinical management: The diagnosis is confirmed
on the basis of the ultrasound findings.
The higher frequency of chromosomal aberrations
and anomalies in monochorionic twins
also has to be taken into account. Detection of
TTTS prior to 20 weeks of gestation has an unfavorable
prognosis. The poor prognosis and
high neurological morbidity associated with
early detection should be explained to the
parents, and the option of pregnancy termination
should be discussed. Serial ultrasound scanning
and fetal echocardiography at short intervals
are necessary to detect the development of
cardiac insufficiency. Administration of digitalis
to the mother and repeated aspiration of amniotic
fluid to relieve hydramnios may be considered
as therapeutic options. In recent years,
coagulation of vascular anastomoses using endoscopic
laser surgery has been successful in reducing
the late neurological morbidity. If one
twin dies during the course of pregnancy, the
surviving twin has a very high risk of developing
brain damage; there is a surge of thromboplastic
substances that may cause cerebral infarcts, hydrocephalus,
and periventricular leukomalacia.
In this case, it is difficult to determine whether
early delivery of the surviving twin has a benefit.
In the United Kingdom, where fetocide is socially
acceptable as an option for terminating pregnancy,
it is being debated whether the pregnancy
should be continued for 3–4 weeks after
the intrauterine death of one twin, retaining the
option of fetocide if severe neurological signs appear
in the surviving twin. In severe cases of
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