Twin Anemia Polycythemia Sequence

Twin anemia polycythemia sequence (TAPS) is a condition that occurs in a twin pregnancy in which the two fetuses share a placenta (monochorionic). TAPS is caused by a continuous transfer of blood from one twin to the other twin through blood vessels in the placenta. The result is that one twin becomes anemic (low red blood cells) and the co-twin becomes polycythemic (too many red blood cells).

TAPS can develop spontaneously in rare cases. It can also occur after treatment for twin-twin transfusion syndrome (TTTS) with either amnioreduction (draining excess amniotic fluid) or fetoscopic laser surgery.

How Do We Diagnose TAPS?

To diagnose TAPS, our team first confirms that the twins share a placenta; this typically happens via ultrasound early in the pregnancy. We also confirm the absence of polyhydramnios-oligohydraminos (abnormally high and low levels of amniotic fluid).

The diagnosis of TAPS is based on a parameter developed by the UH maternal-fetal medicine specialists. The team will perform a fetal Doppler study to measure the flow of blood in each twin and confirm if there is a difference in speed of blood flow between the twins. In TAPS, the “donor” twin will have thinner blood that moves faster than normal and the “recipient” will have thicker blood that moves slower.

Management and Treatment for TAPS

There are several ways to manage TAPS. The team at UH individualizes the treatment based on several factors, including gestational age and the severity of TAPS. Treatment methods include:

• Observation: In less severe cases, the pregnant woman will be monitored via regular Doppler ultrasounds to see whether symptoms remain stable or progress.
• Intrauterine transfusion: An intrauterine blood transfusion may be given to the anemic twin in certain cases.
• Fetoscopic laser surgery: Surgery may be performed to disconnect some of the blood vessels in the placenta to stop the sharing of blood between the donor and the recipient.
• Laser treatment combined with intrauterine transfusion
• Delivery: If TAPS is diagnosed later in gestation, an early delivery can help prevent further complications.