What is TTTS?

Posted On: November 3, 2023 By CIW

Twin pregnancies can bring special challenges, especially when rare complications occur. One such rare (and serious) complication is called twin-twin transfusion syndrome (TTTS), which specifically impacts monochorionic twins, or twins that share a placenta. Being aware of this occurrence is important for women with twin pregnancies because it can guide their maternal care in unique ways. Here is a guide to TTTS with Dr. Nahla Kalek, an OB-GYN from the Children’s Hospital of Philadelphia, one of the most respected and premier fetal centers in the United States.

What is TTTS?

TTTS is a disease of the placenta where the two fetuses sharing a placenta receive unequal amounts of blood volume. This happens because abnormal blood vessels form in the placenta, causing blood to flow unevenly between the fetuses. Dr. Kalek says, “It basically means that one baby is hypervolemic, has too much blood volume, and the other baby is hypovolemic, doesn’t have enough blood volume.”

There is, unfortunately, nothing that can prevent TTTS. According to Dr. Kalek, incident data shows that TTTS occurs in about 10-15% of monochorionic pregnancies. Although rare, she says, “It’s not insignificant.”

The Impact of TTTS

There’s no known cause of TTTS, but it can have a significant impact on the health of both fetuses as the pregnancy develops. Because they receive unequal amounts of blood, each fetus begins to cope differently. Most notably, the fetus with too little blood volume (sometimes called the donor) experiences poor growth and insufficient amniotic fluid. The other fetus, called the recipient, can experience strain on the heart because of extra blood flow, ultimately experiencing a high risk of heart failure.

Dr. Kalek says, “So both babies get sick over time, each in their own way. And it’s all because they’re trying to, sort of, accommodate to this new [blood] redistribution, primarily driven by these artery-to-vein communications that occur within the placenta.”

TTTS is often fatal for one or both twins without intervention from a maternal-fetal medicine specialist. It can also result in premature birth – however, with early successful treatment, it’s possible for both babies to have only mild complications.

Diagnosing TTTS

Early diagnosis of TTTS is key to achieving a good outcome. Careful and often monitoring is recommended so your maternal-fetal medicine specialist can intervene if the condition worsens. Dr. Kalek says of this, “So the ideal is, you know, maybe you get your ultrasound at 8 weeks, 10 weeks, 11 weeks, 12 weeks, make sure to establish chronicity at that point. And then once you’ve established chronicity, meaning one placenta versus two placentas, if it’s one placenta, you need to start doing ultrasound surveillance beginning at 16 weeks, not coming back at 18 weeks or 20 weeks for an anatomy survey.”

Because TTTS can lead to significant complications for your twin pregnancy, it’s important to establish whether you’ll be at risk for TTTS if you discover you’re carrying twins. Dr. Kalek says, “I think also it’s really important… [patients] advocate for themselves when you get that ultrasound as early in the pregnancy as possible and they tell you you have twins, you really wanna insist that they figure out if they’re monochorionic or dichorionic, that really helps shape how the rest of the pregnancy goes.”

High-Risk Pregnancy Imaging with Carnegie Imaging for Women

TTTS requires expert care from our award-winning team of maternal-fetal medicine specialists. To schedule an appointment and learn more about your treatment options, contact Carnegie Imaging for Women through our online form today.

Learn more about TTTS from Healthful Women, our podcast dedicated to women’s health, pregnancy, and wellness.

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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