Twin to Twin Transfusion Sydrome

Invasive Therapies

Amniotic fluid manipulation such as with amniodrainage and septostomy may relieve symptoms and may alleviate problems of TTTS in some patients However, since the anastomoses remain open, the risks of unbalanced volume exchange also remain - the underlying problem is not "fixed".

Closing the anastomoses, if done safely, would end the cause of TTTS, and keep it from recurring - actually treating the problem. This required advances in technology to enter the uterus and close those vascular connections directly. Such instruments (long, thin telescopes with excellent optic properties, called fetoscopes) were developed and have become increasingly miniaturized over the past decade, making intrauterine treatment a real possibility. For each of these invasive procedures, the uterus is entered with a thin needle called a trochar, inside a hollow tube called a sheath. After insertion, the trochar is withdrawn, leaving the sheath as an entry for passage of fetoscopes, specialized instruments or laser fibers.

Early experience with these procedures helped us recognize that closing the anastomoses addresses the shunting of blood volume through the open communications but does not correct the disproportions in placental sharing. In other words, the blood volume imbalance is cured, but the placental territory (donor - small, possibly deficient placenta; recipient - very large, high volume placenta) cannot be reversed. Taking this into account, two principal philosophies of invasive therapy for TTTS have evolved.

Umbilical cord occlusion of one twin limits the potential for rapid hemorrhage between the two twins at the expense of sacrificing the life of one twin. An adequate placental territory to maintain normal growth of the surviving twin is typically maintained.

Fetoscopic laser ablation of placental vascular anastomoses coagulates the vascular anastomses that cause for TTTS. However, closing those vessels to separate the twins' circulations also reduces functional placental territory - what remains may not be adequate to sustain normal growth of both twins. Selective sparing of normal placental vessels is extremely important to ensure the best possible outcomes.

Umbilical Cord Occlusion

This procedure is done inside the uterus, through a sheath placed by ultrasound guidance in the sac of one twin, usually the donor (smaller) twin. Special tweezers grasp the cord and an electric current passes between the jaws of the tweezers, coagulating the blood vessels of that twin's cord. This stops the flow of blood in the cord and that fetus will die.

Because their circulations are no longer connected, the surviving baby usually has no long-term effects from the death of his co-twin. As with any intrauterine invasive procedure, there may be short term complications, including preterm labor, rupture of membranes, infection or bleeding. This means that not all such procedures result in one living baby. But, in about 90% of cases, the procedure results in one living baby, born near term, with no permanent handicaps. For an experienced team, this procedure is technically feasible and usually not long, so maternal operative complications are very unusual. For prevention of infection and preterm delivery, intravenous antibiotics and magnesium as well as oral indomethacin are given on the day of surgery and the following day. Indomethacin is an anti-inflammatory agent used in rheumatoid arthritis, which has excellent success at stopping preterm labor.

Because the umbilical cord is completely blocked, this procedure means survival of both babies can never occur. This procedure may be the best if one twin seems to have damage or abnormalities already, or has IUGR too severe for survival.

Laser Coagulation

Laser ablation of placental anastomoses was pioneered in the US and has been performed for over 10 years in North America and and Europe. The procedure aims to treat the underlying cause for TTTS by coagulating the vascular anastomoses with a laser beam.

Ultrasound is used to identify the placental cord insertion of each baby (colored points).

A large needle in a hollow tube (sheath) is directed by ultrasound into the amniotic sac of the recipient twin. The needle part is withdrawn and an optical instrument like a miniature telescope (called a fetoscope) is passed through this sheath. The fetoscope is used to visualize the connecting vessels. A laser fiber is also passed down the sheath, and the vessels are then coagulated (sealed shut) with the laser. Coagulating the vessels stops the blood flow between the donor and the recipient within the placenta. The coagulation is done on the surface of the placenta, in the territory between the twins, where the imbalanced blood volume sharing takes place. The umbilical cords themselves are not interfered with.

An advantage of this therapy is treatment of the underlying cause with a single procedure. Following the closure of all connecting vessels during the procedure both twins have a chance for subsequent normal development. One limitation is that it is available in only selected centers worldwide. Insertion of the fetoscope may result in rupture of membranes, preterm labor and infection, in up to 10% of patients. There is also a small risk that perforation of small blood vessels in the abdominal wall or on the uterus results in maternal bleeding. Injury to the uterus may require cesarean section or in rare circumstances hysterectomy (removal of the uterus). There is also the theoretical risk of injury to other abdominal organs of the mother, including the bowel, which then may require surgical intervention, and opening of the abdomen. The overall risk for these complications is approximately 1-2%. For prevention of infection and preterm delivery intravenous antibiotics and magnesium as well as oral indomethacin are given on the day of surgery and the following day. Indomethacin is an anti-inflammatory agent used in rheumatoid arthritis, which has excellent success at stopping preterm labor.

After successful treatment, the donor bladder begins to fill (small black circle in the middle of the abdomen) and the blood flow in the umbilical cord improves (right image).

On the recipient side, there is gradual improvement in heart failure from the abnormal tracing before the laser treatment (part of the blood flow in the heart cycle runs backwards, on the left) to normal cardiac function with all blood flow forward (on the right).

To date approximately 1000 procedures have been performed in five major European centers as part of a collaborative trial (Eurofetus project). Results published after the first 220 procedures show the chance for survival of both twins is 55%, survival of at least one twin is 82% and the risk for loss of both twins is 18%. Some increased risk for neurological damage in surviving babies remains, but is significantly lower than the risk following serial amnioreduction (less than 9%). These data reflect initial results and will tend to improve with experience.

There are several factors that can make the procedure less successful, including :

Anterior placenta (harder to visualize with the 'scope inserted in the mother's side)
Later gestational age (our cutoff is 26 weeks gestation. After that, the particles in the amniotic fluid may make it impossible to do a safe procedure.)
Cervix is already dilated or mother in true preterm labor
Previous amniodrainage. This makes fetoscope insertion dangerous and allows the placenta to fold up, hiding the anastomoses we must visualize to coagulate.

These are relative problems with laser ablation. It remains the best chance of having two healthy surviving babies delivered near term.