TAPS is a rare condition that can happen in identical twins who share one placenta, where tiny placental blood-vessel connections slowly shift blood from one baby to the other—leaving one baby anemic and the other with too many red blood cells. Because amniotic fluid often looks normal, it may take special Doppler ultrasound screening to detect, and treatment can range from close monitoring to fetal therapy and delivery planning.
If you’re facing this diagnosis, it’s understandable to feel overwhelmed—but a specialized fetal care team can help you understand what’s happening and guide you step-by-step through the safest plan for both babies.
Understanding Twin Anemia-Polycythemia Sequence (TAPS)
Understanding Twin Anemia-Polycythemia Sequence (TAPS)
The Fetal Center at Riley Children’s Health provides expert care for identical twins who share one placenta. This type of pregnancy is called monochorionic. One possible complication in these pregnancies is twin anemia polycythemia sequence (TAPS).
TAPS is a rare condition where tiny blood vessel connections in the shared placenta slowly move blood from one baby to the other. Over time, one baby may have too little blood, while the other may have too much.
TAPS is different from twin to twin transfusion syndrome (TTTS). It usually develops slowly and often does not cause big changes in amniotic fluid (the fluid around each baby). Because of this, TAPS can be harder to find without special ultrasound blood flow testing.
What Happens in TAPS?
What Happens in TAPS?
In TAPS, very small blood vessel connections in the placenta allow blood to move slowly from one baby to the other over time.
The Donor Twin (Anemic Twin)
The donor twin gives blood to the other baby and can become anemic, meaning they have too few red blood cells. This may cause:
- A pale appearance on ultrasound (usually only in more severe cases)
- Faster blood flow readings in a brain blood vessel on Doppler ultrasound
- Extra strain on the baby’s heart if the condition becomes severe
The Recipient Twin (Polycythemic Twin)
The recipient twin receives extra blood and can become polycythemic, meaning they have too many red blood cells. This may lead to:
- Thicker blood
- Slower blood flow
- A higher chance of problems if circulation becomes too slow
Even when fluid levels look normal, TAPS can still affect both babies. That’s why careful monitoring is so important.
Risk Factors for TAPS
Risk Factors for TAPS
TAPS can only happen in monochorionic twin pregnancies, when twins share one placenta. It may develop:
- On its own during pregnancy
- After treatment for TTTS, especially after fetoscopic laser surgery
TAPS is less common than TTTS, but it still needs close follow up because it can become serious.
How is TAPS Diagnosed?
How is TAPS Diagnosed?
TAPS is diagnosed using a detailed ultrasound and special blood flow testing called Doppler, done by a maternal fetal medicine specialist.
A key part of the exam measures blood flow in a brain artery in each baby, called the middle cerebral artery (MCA). This measurement is called MCA peak systolic velocity (MCA PSV).
- In the donor twin, MCA PSV is higher than expected (a sign of anemia)
- In the recipient twin, MCA PSV is lower than expected (a sign of polycythemia)
Because amniotic fluid levels are usually normal, a routine ultrasound may not detect TAPS. Doppler screening is an important part of care for monochorionic twin pregnancies.
Sometimes TAPS is confirmed after birth when blood tests show different hemoglobin levels (red blood cell levels) in the two babies.
How is TAPS Treated?
How is TAPS Treated?
Treatment depends on how severe TAPS is, how far along the pregnancy is, and how both babies are doing.
Close Monitoring
If TAPS is mild, your care team may recommend:
- More frequent ultrasounds
- Repeat Doppler tests to track blood flow
- Watching closely for any changes over time
Fetal Therapy Options
If TAPS becomes more serious or continues to worsen, treatment options may include:
- Fetoscopic laser treatment – a minimally invasive procedure to seal off the placental blood vessel connections
- Intrauterine transfusion – giving blood to the anemic baby before birth
- Partial exchange transfusion – reducing red blood cells in the baby with polycythemia (in select cases)
Your fetal therapy team will talk with you about these options and recommend a plan that’s right for your pregnancy.
Delivery Planning
If TAPS reaches a critical stage, your care team may recommend early delivery to give both babies the best possible chance for a good outcome.
Why choose the Riley Fetal Center for TAPS
The Fetal Center at Riley Children’s Health offers:
- Experience caring for monochorionic twin conditions, including TAPS, TTTS, and selective growth restriction
- Advanced ultrasound and Doppler imaging
- Access to fetal therapy, including minimally invasive fetoscopic procedures when appropriate
- A team based approach with specialists in high risk pregnancy, pediatric surgery, and newborn care
Locations
Locations
Locations
In addition to our primary hospital location at the Academic Health Center in Indianapolis, IN, we have convenient locations to better serve our communities throughout the state.