About Twin-to-Twin Transfusion Syndrome
Diagnosis and treatment
Who Gets It?
Not all twins are at risk for the condition. It only affects a percentage of monozygotic twins, those individuals resulting from one egg. Depending on when the egg splits and implants, monozygotic twins may develop individual placentas or share a single placenta. TTTS only occurs when there is a single, shared placenta.
The term monochorionic describes twins that are joined in a single chorion, the membrane that attaches to a single placenta. Only monochorionic twins are at risk for TTTS because they are the only type whose circulatory systems may connect through the placenta. Although there has been some speculation that two fused placentas could develop a circulatory connection susceptible to TTTS, researchers of the disease confirm that it is simply not feasible.
TTTS only affects monozygotic twins. It occurs in about a third of monochorionic pregnancies, or less than 10 percent of all identical twins. If untreated, it has as much as an 80 percent fetal mortality rate.
How Is It Diagnosed?
One of the reasons that a multiple pregnancy is subjected to closer scrutiny is so TTTS can be detected. Doctors use ultrasound to assess the risk by determining the number of placentas. If there is just one, subsequent ultrasounds will follow the babies' growth and development, as well as the amount of amniotic fluid, to confirm that it remains equalized. If a discrepancy develops, further ultrasound testing may reveal the presence of too much or too little amniotic fluid around each baby, a sure sign that a shared circulatory connection is shunting blood between the babies.
What Can Be Done?
In past times, babies affected by TTTS were doomed. Without ultrasound technology to detect the disorder, it was likely that one or both of the babies would die in utero, or that they would be born too early to survive. Now, not only does sonography enable doctors to diagnose the condition, new treatments allow it to be cured.
Up until very recently, the primary treatment approach was to stave off preterm labor until the babies were viable and could be delivered. This was accomplished by draining the excess fluid surrounding the recipient twin. Amnioreduction, a procedure similar to amniocentesis, was performed at regular intervals to remove fluid from the recipient baby's amnionic sac. While it is generally effective in stabilizing the situation, it carries the same risks as amniocentesis, including infection and miscarriage. It also does not compensate for the damage occurring to the donor twin.
In the 1990s, Dr. Julian DeLia developed an amazing procedure that allows doctors to correct TTTS by using a laser to seal off the connections in the placenta. The procedure is performed while the babies are still in utero, using a fetoscope, a powerful telescope allowing a surgeon to see inside the womb through a tiny incision. A 2004 study confirmed that this procedure, fetoscopic laser coagulation, produces a better outcome for the babies.
Treatment for TTTS depends on how far along you are in your pregnancy, and to which stage the disease has progressed. Fetoscopic laser surgery is available in half a dozen facilities in the United States as well as other locations in Australia and Europe. As studies confirm its success in treating TTTS, it will become more widely available in the next few years.
From The Everything Twins, Triplets, and More Book Copyright © 2005, F+W Publications, Inc. Used by permission of Adams Media, an F+W Publications Company. All rights reserved.
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