What is twin-to-twin transfusion syndrome?

Twin-to-twin transfusion syndrome (TTTS) is a serious condition that occurs in about 10-15% of identical twin pregnancies where the babies share a placenta (monochorionic).

In TTTS, the blood vessels in the placenta form abnormal connections and blood does not flow evenly between the babies. One twin becomes a “donor” and the other becomes a “recipient.” The donor twin pumps blood to the recipient twin. This means that the recipient twin is bigger, has more blood, and makes more urine. This results in too much amniotic fluid (polyhydramnios) and an enlarged bladder. The extra fluid can also strain the recipient twin’s heart. However, the donor twin is smaller, has less blood, little to no amniotic fluid (oligohydramnios), and a smaller bladder.

How do you know if your twins have TTTS?

TTTS is usually found during an ultrasound in the second trimester. Once TTTS is identified, your health care providers will evaluate how serious the TTTS is. They will look at how much amniotic fluid is in each sac, how the donor twin’s bladder is working, and they will look at blood flow in both babies. They may also do an amniocentesis and echocardiogram (an ultrasound of the baby’s heart) if needed.

What treatment is available for TTTS during pregnancy?

The treatment plan will depend on how severe the condition is. Options for treatment include:

• Monitoring with regular ultrasounds: Monitoring allows your providers to regularly check on your twins and look for any signs that TTTS is getting worse.
• Removing amniotic fluid from the recipient twin: Extra amniotic fluid is removed from the larger (recipient) twin. This is only a temporary option and may need to be repeated.
• Laser surgery (known as selective fetoscopic laser photocoagulation or SFLP): This procedure uses a laser to stop the transfer of blood between the babies. It is often the

Without treatment TTTS can cause serious problems for both babies. So it is important that you go to all of your prenatal checkups—even when you’re feeling fine. Twins with mild to moderate TTTS may be at increased risk for premature birth.