Twin Reversed Arterial Perfusion (TRAP) Sequence

Low-risk cases, where the acardiac twin is small and there is little stress on the pump twin's heart, may only require monitoring. With frequent ultrasounds, doctors can keep an eye on the normal twin's health and identify signs of heart failure. If heart failure is identified and the pregnancy is far enough along, then the normal pump twin is simply delivered.

Fetal Treatment

Many efforts have been made over the years to treat TRAP sequence, focused on finding a way to safely stop blood flow to the acardiac mass, thereby protecting the normal pump twin from heart failure or death. The UCSF Fetal Treatment Center pioneered the most successful form of treatment, taking advantage of advanced technology called radiofrequency ablation (RFA) to stop blood flow into the acardiac mass.

The major benefit of the RFA technique compared to other techniques is the size of the instrument used. The RFA technique uses a small needle of about 1 millimeter in diameter, compared to 3 millimeters for instruments used in other procedures. The smaller device leads to fewer complications such as preterm labor and less trauma to the mother. The procedure is performed using real-time ultrasound guidance.

Having pioneered this technique, UCSF has the most experience with it. Our published results on RFA have shown a success rate greater than 90 percent in treating monochorionic/diamniotic TRAP sequence pregnancies, with an average age of 35 weeks gestation at delivery. This compares favorably with other techniques used to treat TRAP sequence, and has dramatically improved the outcome for pump twins in these pregnancies.

Reviewed by health care specialists at UCSF Benioff Children's Hospital.

Related Information

UCSF Clinics & Centers

Fetal Treatment Center
1855 Fourth St., Second Floor, Room A-2432
San Francisco, CA 94158
Phone: (800) 793-3887
Fax: (415) 502-0660
Appointment information