| TWIN-TO-TWIN
(TTTS) TRANFUSION SYNDROME
BACKGROUND Twin-To-Twin transfusion syndrome (TTTS)
is a rare condition that afflicts about 10% of twins that share
the same placenta (monochorionic twins). The cause of TTTS is
attributed to unbalanced flow of blood through vascular channels
that connect the circulatory systems of each twin via the common
placenta. The shunting of blood through the vascular communications
leads to a net flow of blood from one twin (the donor) to the
other twin (the recipient). The donor twin develops oligohydramnios
(low amniotic fluid) and poor fetal growth, while the recipient
twin develops polyhydramnios (excess amniotic fluid), heart failure,
and hydrops. If left untreated, the pregnancy may be lost due
to lack of blood getting to the smaller twin, fluid overload and
heart failure in the larger twin, and/or preterm (early) labor
leading to miscarriage of the entire pregnancy. A new treatment
approach consists of using laser energy to seal off the blood
vessels that shunt blood between the fetuses. Because the surgical
approach is via an operative fetoscope, there is minimal risk
to the mother. Laser therapy for TTTS has been shown to provide
improved pregnancy outcomes compared to alternative therapies.
Further information regarding pregnancy outcomes is detailed in
the management options and outcomes section below.
DIAGNOSIS & STAGING
The in utero diagnosis of TTTS is established by ultrasound.
First, the presence of a monochorionic twin gestation should be
confirmed. Usually ultrasounds performed earlier in the pregnancy
may be useful in establishing the chorionicity (number of placentas).
Ultrasound findings such as a single placenta, same fetal sex,
and a “T-sign” in which the dividing membrane inserts
perpendicular to the placenta are helpful in diagnosing a monochorionic
twin gestation.
TTTS is then diagnosed simply by assessing the discordance of
amniotic fluid volume on either side of the dividing fetal membranes.
The maximum vertical pocket (MVP) of amniotic fluid volume must
be greater than or equal to 8.0 centimeters in the recipient’s
sac, and less than or equal to 2.0 centimeters in the donor’s
sac.
Once the diagnosis of TTTS is established, the severity of the
condition may be assessed using the Quintero Staging System, as
listed below. This staging system is based on the observations
of several hundred patients with TTTS. Not only does this staging
system mirror the progression of disease, but it has also been
shown to be important in establishing the prognosis. An atypical
presentation of TTTS may occur if the fetal bladder of the donor
twin remains visible despite the presence of critically abnormal
fetal Dopplers or hydrops.
QUINTERO STAGING SYSTEM
- Stage I: The fetal bladder of the donor twin remains visible
sonographically.
- Stage II: The bladder of the donor twin is collapsed and not
visible by ultrasound.
- Stage III: Critically abnormal fetal Doppler studies noted.
This may include absent or reversed end-diastolic velocity in
the umbilical artery, absent or reverse flow in the ductus venosus,
or pulsatile flow in the umbilical vein.
- Stage IV: Fetal hydrops present.
- Stage V: Demise of either twin.
MANAGEMENT OPTIONS & OUTCOMES
Untreated, TTTS that presents before 28 weeks gestation is associated
with approximately 90% perinatal mortality rate. Because of the
dismal prognosis of TTTS, various treatment methods have been
advocated. Recent studies have shown improved outcomes in patients
treated with laser therapy compared to the traditional method
of serial amnioreductions (Quintero, AJOG, 2003; Senat, NEJM,
2004). In the European randomized trial, the study was interrupted
prematurely because statistical improvement in pregnancy outcome
in the laser therapy group was achieved at the time of an interval
analysis (Senat, NEJM, 2004). The treatment options along with
expected pregnancy outcomes are listed below.
- Laser Surgery: This surgical approach utilizes an
operative fetoscope to deliver laser energy that then seals
off the offending blood vessels on the surface of the common
placenta. Because the vascular connections between the two fetuses
are sealed, no further blood exchange between the fetuses takes
place, thus eliminating the syndrome. Pregnancy outcomes after
laser therapy for TTTS is as follows: approximately 85% of patients
will have at least one fetus survive, 50% will have both survive,
with a 5% risk of neurologic sequelae such as cerebral palsy.
These results remain consistent regardless of Quintero Stage
(i.e. severity).
- Alternative Therapies: Possible management alternatives
for TTTS include the following:
- Expectant Management – In this option
the pregnancy would be followed with serial ultrasound examinations.
There is approximately a 90% pregnancy loss rate in cases
of TTTS diagnosed before 28 weeks gestation.
- Amnioreduction – The purpose of this
procedure is to remove excess amniotic fluid from the recipient’s
sac in order to prevent premature birth or miscarriage. This
procedure is done via a needle placed using ultrasound guidance.
Because this approach does not treat the underlying cause
of TTTS, amniotic fluid excess may recur, resulting in the
need for multiple amnioreductions. Overall, the success rate
of this treatment approach is approximately 66% chance of
at least one fetal survivor, with an incidence of 15% chance
of brain damage. Unlike laser therapy, the risk of fetal death
and neurologic sequelae increases with increasing Quintero
Stage.
- Umbilical Cord Occlusion – This procedure
utilizes an operative fetoscope to interrupt the flow of blood
through the umbilical cord of one of the fetuses. This fetus
dies and remains inside the uterus for the duration of the
pregnancy. The remaining twin will have an 85% chance of survival,
and 5% risk of brain damage. Because the risks of this procedure
are similar to laser therapy, but laser therapy provides the
additional benefit of the chance of survival for both twins,
this procedure is not offered for the treatment of TTTS by
the CHLA-USC Fetal Therapy Program.
- Interruption of the Pregnancy – Pregnancy
termination may be chosen as an option up to 24 weeks gestation
in California. The CHLA-USC Fetal Therapy Program does not
offer this procedure.
- Other – Fetal septostomy has been suggested
as a treatment option for TTTS. This procedure entails the
purposeful needling of the dividing membrane in the hopes
to equalize the amniotic fluid within each sac. Studies have
not shown improved outcomes using this approach. Moreover,
the disruption of the dividing membrane may result in cord
entanglement, which may be an additional cause of fetal death.
We advise against this procedure. If this procedure has been
purposely done, you will not be a candidate for laser surgery
at CHLA-USC Fetal Therapy Program.
CANDIDACY FOR LASERY SURGERY
To qualify for laser surgery, the following criteria must be
met:
Inclusion Criteria:
- Gestational age: 16 weeks 0 days to 26 weeks 0 days.
- Diagnosis of TTTS
- Single (shared placenta) with thin dividing membrane
(or no dividing membrane in the case of monoamniotic twins)
- Polyhydramnios: maximum vertical pocket of 8 centimeters
or more in the recipient twin, prior to amnioreduction
- ligohydramnios: maximum vertical pocket of 2
centimeters or less in the donor twin, prior to amnioreduction
- Same gender, if visible
Exclusion Criteria:
- One or both babies have other major birth defects.
- Genetic studies showing an uncompensated abnormality.
- A hole in the dividing membrane that was intentionally made.
- Ruptured fetal membranes (leakage of amniotic fluid from the
vagina).
- Chorioamnionitis (infection in the uterus).
- Ultrasound evidence of brain damage of either fetus.
- Placental abruption (separation of the placenta from the
uterus).
- Active labor.
- Unable or unwilling to participate in observational study
or to be followed up.
LASER SURGERY – DETAILS OF THE PROCEDURE
All surgeries are performed under local anesthesia with some
intravenous sedation. A small incision (3 millimeters or about
1/10th of an inch) will be made and a trocar (small metal tube)
will be inserted into the amniotic sac of the recipient twin.
Amniotic fluid may be sent for genetic and microbiology studies.
An endoscope (medical telescope) will be passed into the uterus.
The blood vessels, which are visible on the surface of the placenta,
will be analyzed, and all communicating vessels will be sealed
off with laser energy. A second trocar may have to be inserted
to complete the surgery, particularly if the placenta is anterior.
At the conclusion of the surgery, the excess amniotic fluid may
be drained from the sac of the recipient twin. You will be given
antibiotics before and after surgery.
LASER SURGERY - POSTOPERATIVE CARE
Typically, you will remain in the hospital for 1 to 2 days after
surgery. You will then be sent home to the care of your primary
obstetrician and perinatologist. Weekly ultrasound is recommended
for the four weeks after surgery. Then, depending on the clinical
circumstances, follow up ultrasounds may be performed every 3
to 4 weeks for the duration of the pregnancy. Details of the delivery
and information regarding the health of the infants will be requested.
You and your doctor will be asked to assist in sending your placenta
fresh to the CHLA-USC Fetal Therapy Program in an icebox container
for evaluation.
RETURN TO TOP »
RETURN TO HOME »
RETURN TO PREVIOUS »
|
OTHER
TTTS LINKS |
