What is twin-twin transfusion syndrome (TTTS)?

Twin-twin transfusion syndrome (also called TTTS or twin-to-twin transfusion syndrome) is a condition in which the blood flows unequally between twins that share a placenta (monochorionic twins). TTTS occurs in about 10 to 15 percent of monochorionic, diamniotic (two amniotic sacs) twins.

The most important step in evaluating a twin pregnancy for twin-twin transfusion syndrome is to determine whether the twins share a single placenta. An ultrasound examination early in pregnancy (during the first trimester) can best make this distinction.

Twin-twin transfusion syndrome can also have a huge impact on the cardiovascular system in twins. It is important that twins with TTTS are thoroughly evaluated for heart problems while in utero.

Symptoms of twin-twin transfusion syndrome

In twin-twin transfusion syndrome, there is an unequal sharing of blood that passes between twins through blood vessel connections in the placenta. One twin (called the donor twin) pumps blood to the other twin (called the recipient). This causes the recipient twin to receive too much blood and the donor twin to receive too little.

The increased volume of blood causes the recipient twin to produce more than the usual amount of urine, which can result in a large bladder, too much amniotic fluid (known as polyhydramnios) and hydrops, a prenatal form of heart failure. The donor twin, who receives too little blood, produces less than the usual amount of urine. This results in low or no amniotic fluid surrounding it (oligohydramnios) and a small or absent bladder.

Without intervention, the condition can be fatal for both twins.

Twin-twin transfusion syndrome treatment

Management of twin-twin transfusion syndrome may include any of the following:

• Expectant management — In situations where surgery is not yet indicated, close monitoring with periodic ultrasound examinations is used to evaluate the condition of both twins and look for signs of progression. In some cases, a follow-up fetal echocardiogram is used as well to look for signs of cardiac changes; these may sometimes be seen before other changes.
• Fetoscopic selective laser ablation — A minimally invasive surgery performed on the placenta to disconnect the communicating blood vessels. This procedure, also called selective laser photocoagulation (SLPC), stops the sharing of blood from the donor to the recipient, with the goal of halting the progression of twin-twin transfusion syndrome. This is typically the preferred treatment for TTTS, depending on gestational age at presentation, location of the placenta and stage of TTTS.
• Amnioreduction — Removal of excess amniotic fluid from the larger twin (recipient), which may help ease any pain or discomfort experienced by the mother due to fluid buildup. This is a temporary treatment option and may need to be repeated.
• Selective cord occlusion — A minimally invasive surgery that stops the blood flow to one twin in order to maximize the outcome for the other twin. Selective cord occlusion procedures include radiofrequency ablation (RFA) and bipolar cord coagulation (BCC). This is considered a last resort option when the disease is very advanced and the at-risk twin is not going to survive. This intervention can protect the co-twin from neurologic impairment and/or death.

Mothers undergoing a fetal surgery procedure will stay in our Garbose Family Special Delivery Unit (SDU), the first birthing unit within a pediatric hospital dedicated to healthy mothers carrying babies with serious and life-threatening birth defects.