6. Twin-to-Twin Transfusion Syndrome (TTTS)
Twin-to-twin transfusion syndrome (TTTS), also called chronic intertwin transfusion syndrome,
occurs only in identical twins who share the same placenta. The
condition can range from mild to severe and can occur at any point
during pregnancy, even at birth.
TTTS cannot be prevented; it’s not a
genetic disorder nor a hereditary condition. We believe it occurs in 5
to 10% of all identical-twin pregnancies. These problems do not occur
in twins who each have a placenta.
In TTTS, twins also share some of the
same blood circulation. This allows the transfusion of blood from one
twin to the other. One twin becomes small and anemic. Its body responds
by partially shutting down blood supply to many of its organs,
especially the kidneys, which results in reduced urine output and a
small volume of amniotic fluid.
The other twin grows large, overloaded
with blood. It produces excessive amounts of urine so it is surrounded
by a large volume of amniotic fluid. Its blood becomes thick and
difficult to pump through its body; this can result in heart failure,
generalized soft-tissue swelling and death.
When a Multiple Pregnancy Isn’t a Multiple Pregnancy
Some women are told early in pregnancy
they are carrying twins, only to discover later they are carrying only
one baby. Early ultrasound exams reveal two babies; later ultrasounds
of the same woman show one baby disappeared, but the other baby is OK.
We believe one of the pregnancies dies and is absorbed by the mother’s
body. This is one reason many healthcare providers prefer not to
predict a twin birth before 10 weeks of pregnancy.
Twins are often very different in size.
There can also be a large difference in their weights. TTTS is a
progressive disorder, so early treatment may help prevent complications.
Symptoms of TTTS
There are symptoms of the syndrome your
healthcare provider looks for. If your abdomen enlarges quite rapidly
over a 2- to 3-week period, it may be caused by the buildup of amniotic
fluid in the recipient twin. The result can be premature labor and/or
premature rupture of membranes. If one twin is small for its
gestational age or one is big for its gestational age, it may indicate
TTTS. In addition, your healthcare provider may suspect TTTS if any of
the following is seen during an ultrasound:
•large difference in the size of fetuses of the same gender
•difference in size between the two amniotic sacs
•difference in size of the umbilical cords
•one placenta
•evidence of fluid buildup in the skin of either fetus
•indications of congestive heart failure in the recipient twin
An additional problem may develop in
either twin. With this condition, fluid accumulates in some part of the
fetus, such as in the scalp, abdomen, lungs or heart.
Diagnosing and Treating TTTS
Report any of the following to your healthcare provider, especially if you know you’re expecting twins:
•rapid growth of your uterus
•abdominal pain, tightness or contractions
•sudden increase in body weight
•swelling in the hands and legs in early pregnancy
The syndrome may also be detected with
ultrasound examination of the uterus. It’s important to find out
whether twins share the same placenta. It’s preferable to learn this in
the first trimester because in the second trimester it can be harder to
discover whether they share a placenta.
If the syndrome is mild or undetected on
ultrasound, the appearance of the babies at birth may identify it. A
complete blood cell count done after birth will show anemia in one twin
and excess red blood cells (polycythemia) in the other.
If diagnosed, the Twin to Twin
Transfusion Syndrome Foundation recommends weekly ultrasounds after 16
weeks until the end of the pregnancy to monitor the condition. They
recommend this be done even if the warning signs of TTTS have decreased.
The most common treatment for TTTS is
amnioreduction, in which large volumes of amniotic fluid are drained
from the sac of the larger twin. A needle is placed through the
mother’s abdomen, and fluid is drained. The procedure is repeated, as
necessary.
In another procedure, a hole punched
between the two amniotic sacs can help equalize the fluid between the
sacs. However, neither of these procedures stops the twin-to-twin
transfusion.
Some cases of TTTS do not respond to
amnioreduction. A small-scope laser procedure may be done to seal off
some or all of the blood vessels the twins share. Usually only one
procedure is necessary during the pregnancy. Survival rates are also
about 60% with this procedure. This treatment is most successful if
done before 26 weeks of pregnancy.
With laser treatment, a detailed
ultrasound exam is done first to help locate the abnormal connection.
Then a thin fiber-optic scope is placed through the mother’s abdomen,
through the wall of the uterus and into the amniotic cavity of the
larger twin. By looking directly at the placenta, blood connections can
be found and sealed with a laser beam. This separates the circulation
of the fetuses and ends twin-to-twin transfusion. However, this
requires doing the procedure while the babies are still in the womb and
may cause complications.
The most conservative treatment is to
watch and wait. The pregnancy is followed closely with frequent
ultrasound exams, with the choice of delivering the twins by Cesarean
delivery if medically necessary.
Newborns with
twin-to-twin transfusion syndrome may be critically ill at birth and
require treatment in a neonatal intensive care unit (NICU). The smaller
twin is treated for anemia, and the larger twin is treated for excess
red blood cells and jaundice.
