Twin-to-twin transfusion syndrome (TTTS)

Ain Shams Journal of Anesthesiology                                         Vol 4-1; Jan 2011
99
Twin-to-twin transfusion syndrome (TTTS)
 
Mohammed Abdel-Galil Sallam MD
Department of Anesthesiology, Intensive Care, and Pain Management, Faculty of
Medicine, Ain-Shams University, Cairo, Egypt
TTTS only occurs in monozygotic
(identical) twins with a monochorionic
placenta. It is the result of an
intrauterine blood transfusion from one
twin (donor) to another twin
(recipient). The donor twin is often
smaller with a birth weight 20% less
than the recipient’s birth weight. The
donor twin is often anemic and the
recipient twin is often plethoric with
hemoglobin differences greater than 5
gm/dL. The blood transfusion from the
donor twin to the recipient twin occurs
through placental vascular anastomoses.
The most common vascular anastomosis
is a deep, artery-to-vein anastomosis
through a shared placental cotyledon.
The clinical feature es of TTTS are
the result of hypoperfusion of the donor
twin and hyperperfusion of the recipient
twin.


The donor twin becomes
hypovolemic and oliguric or anuric.
Oligohydramnios develops in the
amniotic sac of the donor twin.
Profound oligohydramnios can result in
the stuck twin phenomenon in which
the twin appears in a fixed position
against the uterine wall.
Ultrasonography typically fails to
visualize the fetal bladder because of
absent urine.
Either twin can develop hydrops
fetalis. The donor twin can become
hydropic because of anemia and highoutput heart failure. The recipient twin
can become hydropic because of
hypervolemia. The recipient twin can
also develop hypertension, hypertrophic
cardiomegaly, disseminated
intravascular coagulation, and
hyperbilirubmemia after birth.
Monozygotic twins occur in 3-5 per
1 000 pregnancies. Monozygotic twins
can be monochorionic or dichoriomc.
Approximately 75% of monozygotic
twins are monochorionic. Only
monochorionic twins are at risk for
TTTS. TTTS occurs in 5-38% of
monochorionic twins.
Severe TTTS has a 60-100% fetal
or neonatal mortality rate. Mild-tomoderate TTTS is frequently associated
with premature delivery. Fetal death of
one twin is associated with neurologic
sequelae in 25% of surviving twins.
Fetal blood pressure instability can
lead to brain ischemia in either the
donor or recipient twin. Ischemia of the
fetal brain can result in periventricular
leukomalacia, porencephaly,
microcephaly and cerebral palsy. The
more premature the twins are at birth,
the higher the incidence of postnatal
morbidity and mortality.
After delivery, the newborn work-up
should include: Complete blood count,
serum calcium, glucose, creatinine,
platelet count and bilirubin as the donor
twin is frequently anemic at birth,
whereas the recipient twin is frequently
polycythemic at birth, hypocalcemia is
frequently present in the donor twin,
hypoglycemia may be present in either
twin, and may have evidence of renal
dysfunction, thrombocytopenia can
occur in either twin and
hyperbilirubinemia may develop in the
polycythemic recipient twin.
Sonographic findings of TTTS
during pregnancy include significant
discrepancy in size of same-sex fetuses,
monochorionic placentation,
significant disparity in the amount of Twin-to-twin transfusion syndrome                                                            Sallam MA, MD
100
amniotic fluid between the fetuses with
the smaller twin having
oligohydramnios, smaller fetus with an
absent stomach and bladder, these
pregnancies are at risk for preterm
delivery. This may be related to the
uterine overdistention from the twin
gestation and polyhydramnios. Cervical
shortening is also more common so
transvaginal assessment of the cervix
should also be done.
Neonatal imaging should include:
Neonatal brain ultrasonography,
Neonatal echocardiography, Neonatal
renal ultrasonography, Neonatal
abdominal ultrasonography, and
Neonatal chest radiography.
Because ischemia of the brain can
occur during fetal development in
either the donor or recipient twin, brain
ultrasonography should be considered
in both twins born with TTTS. Twins
born prematurely are susceptible to
intraventricular hemorrhage and
periventricular leukomalacia, myocardial
dysfunction, myocardial hypertrophy,
valvular insufficiency, and pericardial
effusions can be detected in either
twin, abnormal renal echogenicity may
be present in either twin and indicates
hypoxic-ischemic cortical necrosis,
ascites pleural    effusions    and
cardiomegaly may be present if
hydrops fetalis occurs.
Treatment:
The   most   common   procedure   to  
treat   TTTS   is reduction
amniocentesis. This procedure involves
draining the amniotic fluid from
around the recipient twin. This
procedure may improve circulation in
the donor twin especially if the
anastomoses are superficial in the
placenta and the TTTS is a lower stage.
This procedure may need to be
performed multiple times during the
pregnancy.
Fetoscopic laser photocoagulation
of chorionic plate vessels is a highly
specialized procedure performed in a
few centers around the world. This is
mostly reserved for more severe cases,
especially those that do not respond to
amnioreduction. In pregnancies treated
with fetoscopic procedures, the overall
survival is 75% with 85% having at least
1 fetus survive. The fetal death rate for
the donor is higher than the recipient
following this procedure.
Timing of delivery depends on
multiple factors. The ideal would be
for delivery at term; however, evidence
of lack of fetal growth or nonreassuring
antepartum testing or preterm labor may
result in a premature delivery.
Medical care of twins after birth is
directed towards problems related to
prematurity, anemia, polycythemia, and
hydrops fetalis. Severely anemic donor
twins may require packed RBC
transfusions or partial exchange
transfusions. Polycythemic recipient
twins may require partial exchange
transfusion to lower serum hematocrit
levels.  Newborns with hydrops fetalis
may require mechanical ventilation,
thoracocentesis, pericardiocentesis, and
paracentesis.
Outcome is dependent upon
gestational age at bir th and whether
intrauterine fetal brain ischemia
occurred. The lower the gestational age
at birth the greater the risk for longstanding neurologic or pulmonary
sequelae. Catch-up growth occurs
postnatally in most of the smaller
donor twins. Ain Shams Journal of Anesthesiology                                         Vol 4-1; Jan 2011
101
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