Twin-to-Twin Transfusion Syndrome (TTTS)

What is TTTS?

Twin-to-Twin Transfusion Syndrome (TTTS) is a rare but serious condition that can occur in pregnancies involving identical twins, especially in cases where the twins share a placenta. It happens when there is an unequal blood flow between the two fetuses through the shared placenta, leading to complications that can affect both twins. This condition typically arises in monochorionic pregnancies, where the twins share one chorion and placenta but may or may not have separate amniotic sacs.

How does TTTS Develop?

TTTS occurs when the blood vessels connecting the twins in the placenta become abnormally linked. In a healthy pregnancy, each twin receives an adequate and balanced supply of nutrients and oxygen from the placenta. However, in TTTS, the abnormal connection of blood vessels causes one twin (known as the “recipient” twin) to receive too much blood, while the other twin (the “donor” twin) is deprived of blood.

• Recipient Twin: The twin who receives excess blood tends to grow larger and may develop complications like heart failure or fluid overload.
• Donor Twin: The twin who is deprived of blood may experience growth restriction, reduced amniotic fluid, and organ underdevelopment.

Risk Factors for TTTS

While the exact cause of TTTS remains unknown, there are several factors that may increase the risk of developing this syndrome:

1. Monochorionic Pregnancy: TTTS is most commonly seen in pregnancies where the twins share a placenta, known as monochorionic diamniotic twins (MCDA).
2. Pregnancy with Identical Twins: Identical twins are at a higher risk for TTTS compared to fraternal twins, as they share a placenta.
3. Assisted Reproductive Technology (ART): Some studies suggest that pregnancies resulting from fertility treatments, such as in vitro fertilization (IVF), may have a higher incidence of TTTS.
4. Previous TTTS Pregnancy: Women who have had a pregnancy affected by TTTS in the past may have a higher risk of it happening again in future pregnancies.

Symptoms of TTTS

The symptoms of TTTS can be subtle or severe, and they may vary depending on the stage of the condition. Common signs include:

• Excess Amniotic Fluid (Polyhydramnios): The recipient twin may cause the uterus to appear larger than normal due to excess amniotic fluid.
• Small or Decreased Amniotic Fluid (Oligohydramnios): The donor twin may experience a noticeable reduction in the amount of amniotic fluid.
• Growth Discrepancies: One twin may be much larger than the other due to unequal blood circulation.
• Doppler Ultrasound Abnormalities: TTTS can be diagnosed through ultrasound scans, which may show irregularities in the blood flow between the twins.

Diagnosis of TTTS

The condition is often diagnosed through routine prenatal ultrasounds. If TTTS is suspected, the healthcare provider may perform additional tests, such as:

1. Doppler Ultrasound: This helps assess blood flow and can identify abnormal connections in the placental blood vessels.
2. Amniocentesis: In some cases, a small sample of amniotic fluid may be taken from the uterus for analysis.
3. Biophysical Profile: This combines an ultrasound with a non-stress test to monitor the health of both fetuses.

Treatment Options for TTTS

Once diagnosed, TTTS requires prompt intervention to manage the condition and increase the chances of a positive outcome. Some of the available options are:

1. Laser Surgery: A procedure called laser photocoagulation may be used to seal off the abnormal blood vessels in the placenta. This helps restore balance by cutting off the blood flow between the two twins.
2. Amnioreduction: In some cases, doctors may drain excess amniotic fluid from the recipient twin to relieve pressure on the uterus and reduce the risk of preterm labor.
3. Fetal Surgery: In rare cases, surgery to separate the twins or to correct other complications may be necessary.
4. Close Monitoring: Continuous monitoring and regular ultrasound exams are critical for tracking the condition’s progress and making necessary adjustments to the treatment plan.

Prognosis and Risks

The outcome of a pregnancy with TTTS depends on the severity of the condition and the timing of intervention. If diagnosed and treated early, the chances of both twins surviving and developing normally increase significantly. However, untreated TTTS can lead to severe complications, including:

• Preterm Birth: Many pregnancies with TTTS result in premature delivery, which increases the risks of complications for both twins.
• Long-term Health Issues: Both twins may face long-term health concerns, such as developmental delays, neurological impairments, or organ damage.

Conclusion

Twin-to-Twin Transfusion Syndrome is a rare but serious condition that requires prompt diagnosis and intervention. Through modern medical technologies such as laser surgery and amnioreduction, many cases of TTTS can be managed successfully, giving both twins a better chance of healthy outcomes. Expectant parents carrying twins should stay informed about the condition and work closely with their healthcare providers to monitor the pregnancy and make necessary decisions to ensure the best possible outcome.