Advanced Fetal Care
Ultrasound-Guided, Intrauterine Laser Ablation for Twin-to-Twin Transfusion Syndrome
Fetal abnormalities such as twin-to-twin transfusion syndrome are routinely and successfully managed with the specialized clinical expertise, technical resources and comprehensive approach to care found at the University of Maryland Center for Advanced Fetal Care.
The Center’s team of specialized physicians, perinatal nurses, genetic counselors and perinatal sonographers boasts many pioneering efforts internationally and nationally. They were the first in North America to insert fetal bladder shunts and to perform intravascular fetal transfusions. They were the first in the mid-Atlantic region to be certified to conduct first-trimester nuchal translucency screening and the first in Maryland to perform ultrasound-guided, intrauterine laser surgery for twin-to-twin transfusion syndrome.
“In Maryland and beyond, our Center is recognized and valued for its unmatched expertise in the care of perinatal complications,” says Christopher Harman, M.D., professor and interim chair, obstetrics, gynecology and reproductive sciences at the University of Maryland School of Medicine. “Through continuing education conferences we sponsor and through our consulting work with community physicians, patients increasingly are being referred to us before pregnancy reaches a crisis stage.”
The leading-edge nature of the Center’s work is typified in its accomplishments with twin pregnancies, in which numerous complications can occur. Underscoring the importance of this focus, Ahmet Baschat, M.D., professor of obstetrics, gynecology and reproductive sciences and director of the Center’s Section of Fetal Therapy, points out, “In the past 10 years, the rate of twin pregnancies has soared more than 400%, and among identical twins, up to 30% can exhibit a complication such as twin-to-twin transfusion syndrome (TTTS). Careful screening is imperative to detect an abnormality before it causes problems. Our Center has the diagnostic capabilities to make an early diagnosis and to determine whether therapy will be needed.”
Laser ablation for twin-to-twin transfusion syndrome
Identical twins sometimes share the same placenta, though most have their own amniotic sac (monochorionic/diamniotic). Lying between the fetuses’ zones is the “equator,” in which placental blood vessels interconnect and the twins exchange blood. Usually the exchange is balanced. In some cases, though, one fetus (donor) may lose blood in the exchange while the other fetus (recipient) gains it. TTTS occurs in 20% or more of mono/di pregnancies and requires constant monitoring. The diagnosis is often suspected as early as 12 weeks gestation.
Early signs of TTTS. With mono/di twins, the Center’s team intensifies monitoring every two weeks to detect the earliest signs of TTTS before it becomes problematic and thereby to help families and their physicians make informed decisions. Ultrasound and Doppler flow analysis can identify discordance in amniotic fluid volume, differences in fetuses’ physical size and increasing thickness of blood.
In receiving the greater proportion of blood, the recipient has too much water and too many blood cells. The recipient excretes more urine, increasing the volume of surrounding amniotic fluid. The recipient’s blood increases not only in volume but in thickness, causing the heart to work overtime and, absent intervention, to become hypertrophic and stiff. The donor, on the other hand, receives too little fluid and too little blood that is also thin, resulting in reduced amniotic fluid, malnutrition and anemia as evidenced by fetal growth restriction (FGR).
Staging TTTS. Stage 1 TTTS is characterized by polyhydramnios in the recipient and oligohydramnios in the donor. In Stage 2, one fetus excretes urine constantly, while the other excretes none at all and its bladder is no longer filling. Stage 3 involves cardiovascular challenges to one or both fetuses. Stage 4 is when one fetus, usually the recipient, exhibits heart failure. Abnormal flow of blood to and from the heart is evident on Doppler ultrasound. Stage 5 involves the death of one fetus, usually the donor. The recipient may be injured further at Stage 5 by losing blood into its dead twin, resulting in permanent brain, heart or other organ damage. When TTTS occurs earlier in pregnancy (as it often does) outcomes are usually poor.
Intervention. Increasing amniotic fluid around the recipient twin distends the uterus and can lead to preterm labor. Until a few years ago, little could be done except to drain fluid in an attempt to delay premature delivery. At times, this procedure paradoxically caused an even greater imbalance. Today the optimal solution is laser coagulation used to interrupt the blood connections in the “equator” region and the proximal zones of shared circulation. Though some blood vessels can be identified with ultrasound, smaller ones may escape detection. However, a scope paired with the laser is just 2.2 mm in diameter (1.1 mm for early pregnancy), allowing for direct visualization of even the smallest vessels and areas of shared blood flow and mapping of the entire surface of the placenta. Risk of ruptured membranes and other complications is also reduced with the use of such small-diameter instruments.
Circumstances likely to yield poor therapeutic results include TTTS that has reached Stage 4, or a donor whose size is 30% smaller than its co-twin. Options and prognoses are discussed thoroughly with parents. In extreme cases, eradicating the shared placental zone leads to the demise of the donor fetus. However, fetal discrepancies are seldom so extreme.
Outcomes have improved dramatically. The laser ablation technique is usually successful with the first attempt, creating a permanent separation in which there is little chance for the regrowth of small vessels. Close monitoring continues in the weeks following the procedure to observe for possible fluid imbalance. The donor usually recovers without residual damage and catches up with its twin. Cardiac sequelae in the recipient may heal before birth, but care after birth may also be needed. Today, at least one healthy baby survives in 80% to 90% of cases, and both babies do well in up to 70% of cases.
Seamless perinatal and postpartum care
As delivery draws near, the Center coordinates ongoing care for infants with the Children Hospital’s Neonatal Intensive Care Unit and a team of neonatologists, pediatric cardiologists and pediatric surgeons. In contrast to centers that have pediatric-focused programs but lack full-range obstetric services, the Center for Advanced Fetal Care offers seamless care for both mother and child. It is uniquely equipped to care for mothers throughout the perinatal and postpartum periods. With access to full maternal services, the Center has the infrastructure to successfully manage such issues as preterm labor, cervical shortening, ruptured membranes or maternal medical complications.
When there is any doubt about the well-being of a pregnancy, the Center for Advanced Fetal Care can help provide the best possible treatment. To learn more, call 410-328-3865.
This page was last updated: November 7, 2013