Summer 2005

Sharing the Womb Can Be Deadly

Twin-twin transfusion syndrome (TTTS) is a serious complication of monochorionic twin gestation. This syndrome is caused by vascular connections in the shared placenta that lead to the uneven distribution of blood between identical twins. The donor twin gets less blood, is smaller and is surrounded by less amniotic fluid. The recipient twin gets too much blood, is larger and is surrounded by a large volume of amniotic fluid. The diagnosis is made in the second trimester of pregnancy.

TTTS progressively worsens over time. The donor twin, with access to less blood, grows more slowly and develops kidney failure and eventually heart failure. The recipient twin, in turn, can get too much blood and suffer from high-output heart failure. In the most severe cases, one or both twins may present with hydrops fetalis, a condition seen in heart failure. On the sonogram, the hydropic fetus appears swollen. In over 80 percent of untreated TTTS cases, both of the twins will die. Because of the shared blood connections, if one twin dies, there is a significant risk of the other's dying. Even if the second twin survives, there is a good chance he or she will suffer brain damage.

For many years, the most effective therapy for TTTS was needle aspiration to reduce the volume of amniotic fluid surrounding the recipient twin. Another, more recent method involves cutting key vascular connections on the placenta, thus dividing the twins' blood supply. The vascular connections between the twins on the surface of the placenta are evaluated visually through a fetoscope inserted through the uterine wall. Then, vascular connections are ablated, using a laser.

UCSF Benioff Children's Hospital has been one of the leaders in treating TTTS, and was recently part of a clinical trial sponsored by the National Institutes of Health to evaluate the comparative benefits of amnioreduction versus selective fetoscopic laser treatment.

For more information, contact the UCSF Fetal Treatment Center at (800) RX-FETUS or (800) 793-3887.

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