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300 Longwood Avenue
Boston, MA 02115
(617) 355-6000
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My Child Has:
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Twin-Twin Transfusion Syndrome
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Twin-twin transfusion syndrome (TTTS) is a problem involving the placenta in a twin pregnancy. It can occur when the twins are identical and share a placenta (monochorionic). Almost all identical twins exchange blood across the placenta, although usually the exchange is balanced. In TTTS, the blood connections in the placenta are abnormal and the blood passes unequally between the two fetuses. One fetus, the donor twin, pumps blood to the other fetus, the recipient twin. Without intervention, the recipient twin receives too much blood and may develop fluid overload, heart failure and die and the donor twin may die from not having enough blood, or severe anemia.
TTTS occurs in varying stages of severity, which may or may not progress to the point where intervention is needed.
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The exact cause of TTTS is unknown. There are several variations of blood vessel development that may lead to unbalanced blood exchange. In addition, the fetus' response to altered blood volume may worsen the condition.
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TTTS occurs in approximately 10% of all monchorionic pregnancies in the United States, which amounts to about 2,000 patients per year. (Quintero 2000)
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Twin-twin transfusion Syndrome is diagnosed by ultrasound. Signs of the condition may be noted on a routine prenatal ultrasound, or your obstetrician may refer you for an ultrasound if your uterus measures larger than it should for that week of pregnancy. The discrepancy in measurement doesn't always mean that there is a problem. But if a problem is suspected on the ultrasound, you may be referred to another doctor who specializes in high risk cases for a more detailed Level 3 ultrasound.
Other tests you may encounter include:
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- fetal echocardiography, which is a special ultrasound of a baby's heart.
- a Doppler flow study which may be used to assess blood flow in the umbilical blood vein and arteries, fetal brain, and fetal heart.
- Magnetic Resonance Imaging, used to determine if there is any neurological damage in the donor twin. The MRI takes pictures of the fetus's brain through the mother's abdomen
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Ultrasound findings that point to a diagnosis of TTTS include identical twins with a shared placenta and abnormal communicating blood vessels. Depending on the severity of the condition, the recipient twin may respond to the abnormal amount of blood by having a very large amount of urine in the bladder, with too much amniotic fluid in the sac (polyhydramnios). The donor twin may respond by having little or no urine in the bladder, and too little amniotic fluid in the sac (oligohydramnios). You may hear the doctor refer to this as an oligo/poly sequence. You may also hear the term "stuck twin" which refers to the donor twin, who, with such little fluid in the sac is restricted in movement and can become stuck against the uterus.
There is also a difference in the size and weight of each fetus. The growth restricted donor twin will be much smaller than the recipient twin, which is not only growing more rapidly, but can be swollen with too much blood.
Doctors will also be looking for signs of impending congenital heart failure (hydrops)., which occurs in severe cases of TTTS. Hydrops occurs because the recipient receives too much blood, which in turn can be difficult for the heart to pump. This causes the fetus' heart to work too hard, which can lead to heart failure that may cause the fetus to die. When one twin dies there is a serious risk of death or severe neurological injury to the other fetus. Without treatment, death will occur in about 80% of these cases
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There are several different procedures used to treat TTTS. Which procedure or combination of procedures is used will usually depend on the level of severity of the condition. Some cases of TTTS never progress pass the earliest stages, when there is still urine in the bladder of the donor twin, who never becomes "stuck." These cases would require only close monitoring to ensure that the condition does not progress.
Once the condition progresses, your doctor may advise you to undergo any of the following procedures, all of which are designed to alleviate harmful symptoms until the time of delivery, when the twins no longer need to share a placenta.
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- Serial amniocentesis is a procedure that is used periodically to relieve the recipient twin of the excess accumulation of amniotic fluid. For this procedure, a needle is used to enter the mother's uterus and the recipient twin's amniotic sac, which is drained of fluid.
- Amniotic septostomy is a procedure in which a needle is inserted into the mother's abdomen, and the membrane between the two twins is punctured to allow equilibration of amniotic fluid between the two sacs, giving the smaller fetus more amniotic fluid.
- Umbilical cord ligation (tying of the umbilical cord) is performed endoscopically (through a small puncture in the mother's abdomen) when one twin is severely compromised with impending death. If one twin dies the other is at high risk for neurological damage caused by a severe drop in blood pressure. The procedure should offset the drop in blood pressure and prevent other continued symptoms in the surviving twin.
- Endoscopic laser surgery is a procedure in which a small puncture is made on the mother's abdomen and endoscope is inserted into the amniotic cavity. This allows the surgeon to look into the uterus and use a laser to vessel con or interupt abnormal connections between the twins.
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Very few long-term studies have been performed to assess the outcomes of babies with Twin-Twin Transfusion Syndrome. Some studies have shown, however, that twin fetuses with advanced TTTS have a better survival rate after undergoing either amniotic septostomy or endoscopic laser surgery than those who undergo other treatments discussed above. It is believed that 80% of fetuses with TTTS will die if there is no treatment at all. When one fetus dies, there is a high incidence of brain injury to the other fetus. With umbilical cord ligation, brain injury might be prevented in the surviving twin. Some survivors may do well and be completely healthy, while others may have injuries to their hearts and kidneys. There is also a risk of preterm delivery after these procedures.
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The information on this website should not be taken as medical advice,
which can only be given to you by your personal health care professional. |
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Copyright © Children's Hospital Boston. All rights reserved. |
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