What is fetofetal transfusion?

Fetofetal transfusion, more commonly known as twin to twin transfusion syndrome (TTTS), is a very serious prenatal complication. If your twins have TTTS, one baby will receive too much blood and the other will receive too little. This is due to imbalanced blood vessel connections between the placenta and the twins.

TTTS is usually identified through ultrasounds and prenatal testing before you feel anything more than typical symptoms of pregnancy. When TTTS has progressed, you may experience “maternal mirror syndrome.” This is when your symptoms mimic those of the recipient baby, who has increased cardiovascular activity.

You may experience the following:

  • severe swelling
  • vomiting
  • high blood pressure

Maternal mirror syndrome is rare but serious. Seek medical care if your pregnancy is affected by TTTS and you have any of these symptoms. You may be admitted to the hospital to control your symptoms and to monitor your twins.

Pregnancies with multiple babies and one placenta have an elevated risk of TTTS. This type of pregnancy is usually identified during an early ultrasound. You’ll need to have frequent scans during pregnancy to monitor the size and condition of your twins. According to the Twin to Twin Transfusion Syndrome Foundation, early research suggests links between maternal nutrition and TTTS. If you have a high-risk pregnancy, your doctor may recommend a specific diet, or prescribe vitamins.

TTTS occurs when blood isn’t equally exchanged between both babies.

In some pregnancies with twins, each baby is connected to one shared placenta through its own umbilical cord. Blood vessels spread from each cord into the placenta. Each twin sends blood through these vessels into the placenta. They then receive blood through the veins that have been enriched with oxygen and nutrients. Circulation is balanced — each twin sends and receives blood the same way. Although rare, this situation can be healthy, and is called monochorionic twins. Only identical twins can be monochorionic (one placenta) and therefore only identical twins can have TTTS.

In pregnancies affected by TTTS, one twin, known as the donor, sends blood through the arteries to the placenta, but doesn’t receive enough blood back through the veins. The other twin, known as the recipient, gets more blood through the veins than what was sent to the placenta through the arteries. This is dangerous for both fetuses. The donor is often small in size and deprived of nutrients and oxygen. The recipient has an overloaded cardiovascular system, which may lead to poor heart function.

Most cases of TTTS result from abnormalities of the blood vessels in the placenta. Beyond this, specific causes are often unknown.

Scheduling and keeping regular prenatal appointments is essential to identifying TTTS. Your doctor will usually be able to identify multiples in the first trimester through ultrasound or fetal heart tones. Once your doctor suspects you’re carrying twins, they’ll examine the fetuses by ultrasound. If both twins share one placenta, your pregnancy will be considered high risk. You’ll need to undergo regular scans and prenatal testing.

TTTS is often diagnosed by ultrasound based on the levels of amniotic fluid surrounding each twin. In response to lack of oxygen and nutrition, the donor twin’s kidneys may shut down, resulting in limited amniotic fluid. The recipient twin increases urine output to keep up with the extra amount of blood pumping through their system, causing high levels of fluid in the amniotic sac.

Another sign of TTTS is a difference in each baby’s size. This is a less reliable way of diagnosing the condition. One twin being larger than the other could be normal, or it could be caused by complications.

Prenatal testing such as amniocentesis may be used to confirm a diagnosis of TTTS.

Treatment varies depending on the severity of TTTS and the health of you and your babies. Your goal will be to carry the fetuses until they can be delivered safely, at which point TTTS is usually not a threat. In cases of preterm delivery, there may be complications. The health of the fetuses will be tracked using ultrasound. Fetal MRIs and echocardiograms will assess any problems with the babies’ hearts and brains.

You’ll likely be told to remain on bed rest through the duration of your pregnancy. Nutritional supplements will also be prescribed.

In severe cases, or if delivery is going to happen soon, you may be hospitalized. A minimally invasive laser procedure may be used to interrupt circulation through the placenta. This surgery is usually ordered only when one or both twins are in immediate danger because it carries some risk of injury.

Once your twins are developed to the point where they may be able to survive outside the womb, you and your doctor will need to plan your delivery. Your doctor may recommend inducing labor or a cesarean delivery if it looks like the risks associated with preterm delivery aren’t as threatening as the TTTS.

If left untreated, the outlook for twins with TTTS is poor. Modern advances in medicine give twins affected by TTTS a more positive outlook. Many mild cases of TTTS can be controlled with bed rest and nutritional therapy until delivery is safe.

There are other treatments for TTTS, such as amnioreduction, in which some of the amniotic fluid is removed from the sac of the larger twin. Another procedure, called a septostomy, makes little holes in the membrane that separates the twins. Neither of these procedures fixes the cause of TTTS the way laser surgery does. Each procedure has its risks.

Many cases of TTTS can’t be prevented, but maintaining a healthy diet before and during pregnancy can help to prevent TTTS, or make it less severe if it does occur. Take prenatal supplements as recommended by your doctor. Always attend regular prenatal appointments to monitor your pregnancy.

Incidents of TTTS have more positive outcomes when they are identified early and monitored by doctors. TTTS and its treatment is a very complicated medical condition. Talk to your doctor early in your pregnancy to plan out an approach to treating it.