Twin-to-twin transfusion syndrome (TTTS) is a rare complication of pregnancy that develops in 10-15% of twins when the babies share the same placenta (monochorionic). TTTS can occur with triplet or quadruplet gestations if babies share the same placenta. All babies who share a placenta share blood between them through connecting blood vessels. If the blood is shared equally, the babies will do fine. If there is unequal sharing of blood flow that can cause TTTS. It may develop any time in the second or third trimester of pregnancy.
When babies are diagnosed with twin-to-twin transfusion syndrome, the baby sending more blood to the other will make less urine and have less fluid around them.They may also be smaller. This baby is called the ‘donor’. The baby receiving more blood and has extra fluid around them. This baby usually grows normally and is called the ‘recipient’.
If TTTS develops, it is dangerous for both babies involved. Both babies have a high chance of dying (over 90% for most cases) if there is no treatment. Offering treatment will increase the chance the babies can survive and be healthy. There are possible long term effects even with treatments. The 'donor' may be much smaller and is at higher risk of kidney problems related to not having enough blood flow. The extra blood flow that the ‘recipient’ twin receives can put strain on the heart and cause heart failure or problems with the development of the heart. Both babies have a higher chance of having neurodevelopmental problems (which can be milder disabilities or more severe problems) than babies without TTTS.
A system known as Quintero Staging is used to describe the severity of TTTS:
- Stage I: There is reduced amniotic fluid (oligohydramnios) around the donor. The donor bladder can still be seen. The recipient has extra amniotic fluid (polyhydramnios). A special ultrasound measurement (Doppler) of blood flow moving through the umbilical cord of each baby is normal and bladders are seen on both babies.
- Stage ll: Low fluid and extra fluid persist as above. The donor bladder is no longer seen on the ultrasound exam. The Doppler study shows normal blood flow through the cord of each baby.
- Stage lll: In addition to the findings in Stage l, the Doppler studies in this phase are abnormal in at least one of the babies.
- Stage IV: This stage is used when there is progression to hydrops in one of the babies. Hydrops is when there is extra fluid in the baby’s lungs, abdomen, around the heart, or in the skin. This is usually due to heart failure in the recipient.
Diagnosis of twin-to-twin transfusion syndrome
TTTS is diagnosed from an ultrasound evaluation. Since it can arise quickly, it is important that multiple gestations with a shared placenta be screened and followed closely with ultrasound looking at the amount of fluid around the babies. If TTTS does develop, a fetal echocardiograms is done to evaluate heart function. Sometimes, a fetal MRI of brain anatomy is offered but this is not routinely done. An amniocentesis may be done to assess the chromosomes of both babies if that is desired.
Management of pregnancy
In addition to regular prenatal care for multiple gestations, twins who share a placenta will have more frequent ultrasounds (every 2 weeks) to monitor the health of both babies. Other antenatal testing will be used as the pregnancy progresses.
Fetal treatment of twin-to-twin transfusion syndrome
Fetal treatment is an option for some families. The most common option is selective laser ablation of fetal vessels or laser therapy to treat the underlying cause of TTTS by stopping blood flow through the connecting blood vessels between the babies. This is safely done between 16 and 26 weeks gestation for appropriate patients. Read more about laser therapy to treat TTTS.
If laser therapy is not an option for a patient or if they prefer a different treatment, amnioreduction to remove the extra fluid from around the recipient is offered. Amnioreduction is performed by inserting a needle into the uterus and into the sac of the recipient twin The fluid levels and the babies’ response are monitored with ultrasound while the extra fluid is removed. This changes the blood flow between the babies. 80% of cases will need this done more than one time.
In the past, some patients were offered a treatment called septostomy. This is a procedure that makes tiny holes in the dividing membrane to let amniotic fluid cross the membranes between the babies in an attempt balance the fluid level between them. This is no longer used as it can create additional problems for some pregnancies.
These treatments options are complex and need to be discussed in detail with patients to review all of the options possible. Care needs to be individualized for each patient.
Delivery of babies with twin-to-twin transfusion syndrome
It is recommended that the delivery of a baby with an omphalocele be planned at a hospital that is prepared for high-risk births including a newborn intensive care unit and pediatric surgical services. This will simplify communication between the teams caring for the baby and also limit the separation between mother and baby.
Premature delivery is not uncommon with this condition. This can be due to early labor, early or premature rupture of membranes, or due to complications that result in a recommendation to deliver. Cesarean delivery is more common but is not necessary for all patients.
University of Michigan is one of only a few centers nationwide at which the birth center is co-located within a comprehensive children’s hospital. This unique setting allows for seamless integration between our private-room birth center, state-of-the-art newborn intensive care unit (NICU), and access to around-the-clock pediatric surgical services in one convenient location.
Postnatal treatment of twin-to-twin transfusion syndrome
Many babies with TTTS are born prematurely. Their overall health is often dependent on how early they are born. Because they do have a higher risk for neurological, heart, and kidney problems, they should be followed closely by their pediatrician who should be aware of the pregnancy course and any treatments.
Future pregnancy risk
There is no reason to think TTTS was something that could be prevented or that it was caused by any particular action. This is not something that would be expected to run in families nor to happen in another pregnancy. Your doctor and a genetic counselor will review the risk with you.
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