There is a 10-15 percent risk of TTTS in monochorionic twin pregnancies.
Treating twin-to-twin transfusion syndrome
issue 22 | Fall 2014
Twin-to-twin transfusion syndrome (TTTS) is one of the most serious fetal conditions, with survival rates around 5—10 percent without treatment. The University of Michigan C.S. Mott Children's Hospital and Von Voigtlander Women's Hospital offers a full spectrum of prenatal care management and treatment options — including fetoscopic laser surgery — to treat TTTS.
Patients with a monochorionic twin pregnancy share a blood supply through the placenta. There is a 10—15 percent risk of unequal sharing leading to development of TTTS. TTTS is defined as polyhydramnios in one baby with an amniotic fluid pocket of 8 cm or more (the recipient), and oligohydramnios or decreased amniotic fluid with a less than 2 cm pocket of fluid in the other (the donor). These twins also have an additional 10—15 percent risk of other complications related to the monochorionic status throughout the whole pregnancy.
"Treating TTTS with fetoscopic laser surgery is the best treatment we can offer for this very serious condition," says Marjorie "Marcie" Treadwell, M.D., professor of Obstetrics and Gynecology and director of the Fetal Diagnostic Center at University of Michigan Health System. "Currently, UMHS is the only place in Michigan performing fetoscopic laser for TTTS."
It is important to stress that monochorionic-diamniotic twins should be followed differently than other twin pregnancies. "We recommend an ultrasound at 16 weeks gestation, and ongoing ultrasounds every other week throughout the pregnancy," explains Treadwell. "The ultrasound should evaluate fluid volumes and blood flow looking for evidence of either TTTS, twin anemia polycythemia syndrome (TAPS) or selective intrauterine growth restriction. Most pregnancies that progress to TTTS will do so around 18 to 24 weeks, but it can happen anytime, even as early as 16 weeks."
The decision to use laser intervention is based on ultrasound and fetal echocardiogram evaluation that show TTTS progressive or persistent Stage I with cardiac dysfunction, or at Stage II or greater.
The laser procedure severs all vascular connections between the babies, creating separate blood supplies. Excess amniotic fluid is also removed from the recipient baby.
"After the procedure, we either co-manage the patient with her referring provider or refer her back completely, depending on the circumstances," says Treadwell. "Generally, patients will continue the pregnancy and deliver closer to term, with an average of around 33—34 weeks. A stay in the NICU is often required, but these babies generally do well."