Twin-to-Twin Transfusion Syndrome: Stages & Symptoms

Instructor: Jennifer Reyes

Jennifer has taught Nursing in ADN, BSN, and MSN programs and has a Master's degree in Nursing Education.

This lesson explores the phenomenon of twin-to-twin transfusion syndrome. It discusses the symptoms associated with the syndrome as well as the staging of it.

Twin-to-Twin Transfusion Syndrome
TTTS affects about 15% of twin pregnancies

There are many joyous moments throughout pregnancy. Finding out that you are carrying twins can be one of them. However, carrying twins can be risky for both mother and fetuses. One issue that can occur is twin-to-twin transfusion syndrome (TTTS). This is a syndrome that arises in identical twin pregnancies when both fetuses are sharing one placenta and there is unequal blood flow between the mother and the two fetuses. Twin-to-twin transfusion syndrome has only been reported in about 15% of pregnancies.

Diagnosis of this syndrome can be done via ultrasound. An ultrasound is a type of medical procedure that can produce an image using sound and other vibrations to do so. The picture is taken of a person internally in order to provide a better idea of what is happening to cause their symptoms. This type of medical procedure is very common throughout pregnancy so that physicians can check on and monitor the fetus while it grows inside of the mother.


Diagnosis and staging of this syndrome are based on specific symptoms. Two of the most important symptoms are polyhydramnios and oligohydramnios.

Polyhydramnios refers to an increased amount of amniotic fluid located within the amniotic sac. Whereas, oligohydramnios means the opposite and there are deficient levels of amniotic fluid within the amniotic sac.

The level of fluid is important because it helps support and protect the fetus(es) during pregnancy. Each fetus will have their own amniotic sac while sharing a placenta within the mother's womb.

In addition, Doppler levels will be evaluated within the fetus. Doppler levels are used to measure blood flow to major arteries and vessels. In utero, the biggest artery and veins are found in the umbilical cord connecting mother and fetus. Typically, with TTTS, there will be absent or irregular blood flow in the umbilical artery and umbilical vein.

Ascites refers to the accumulation of fluid in the abdomen. This accumulation of fluid occurs in the fetus(es) and can cause the abdomen to swell and creates pressure on the abdominal organs.

Hydrops is fluid collection in two or more body cavities. This accumulation within the fetus(es) can lead to death.

Fetal demise refers to the death of the fetus. This is not a symptom, but a result of severe TTTS.


When TTTS is diagnosed, via ultrasound, it is also staged. Staging refers to the level of severity the syndrome is occurring at. With TTTS, there are five stages. The staging is made after reviewing both fetus's bladders as well as the level of amniotic fluid within the mother's abdomen. The fetus with more fluid is usually referred to as the recipient fetus, while the fetus who is with less fluid is referred to as the donor fetus.

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