What is Twin to Twin Transfusion Syndrome?

Twin to twin transfusion syndrome (TTTS) is a condition in which blood from one twin (the donor) is transfused into the other twin (the recipient) via blood vessels in their common placenta. It occurs in 15% of identical twins that share a placenta (about two percent of all twin pregnancies). While uncommon, it has potentially serious and life threatening effects upon both twins.

Normally, identical monochorionic twins have blood vessels that connect to each other on the surface of the placenta. Blood can flow from one twin to the other but this flow is balanced in both directions. TTTS occurs when there is a disturbance to this balance and there is a "net" flow of blood from the donor to the recipient twin.

The donor twin decreases the amount of urine that he or she makes, resulting in a drying up of the amniotic fluid around this baby (amniotic fluid consists largely of baby’s urine). Lack of fluid around the baby is known as "oligohydramnios", and this twin is sometimes called a "stuck twin". The recipient twin who gets too much blood tries to get rid of the excess load by making large amounts of urine. The amniotic fluid around this twin rapidly increases and becomes excessive, otherwise called "polyhydramnios".

The recipient twin can receive so much blood that its heart cannot cope with the extra work. The heart often becomes larger and starts to fail. The fetus starts to accumulate fluid in its body cavities and becomes swollen, which is a condition called "hydrops". Once this develops, the life of this twin is seriously threatened. The growth of the donor twin is also often impaired. In severe cases, this twin is also at risk of dying from lack of nutrition.

When does TTTS occur? What happens if it is not treated?

This condition normally develops in mid-pregnancy from about 16 weeks to about 28 weeks. The mother generally notices that her abdomen rapidly increases in size, sometimes even larger than a full term pregnancy. The mother may also experience tightening, lower abdominal pain, lower backache, and swollen feet and ankles. If left untreated, the large amount of fluid can cause the mother to either break her waters and/or go into preterm labour. Untreated, very few twins survive TTTS.

This condition can also lead to the loss of one of the twins before delivery. If one monochorionic twin were to die in the womb, the vascular connections in the placenta can cause significant risk to the co-twin. During the moments around death, the fall of blood pressure in the sick twin causes further acute transfusion from the co-twin. In about half of these cases the transfusion is very small and the co-twin can survive and remain well. In about a quarter of these cases, the co-twin loses so much blood that he/she also dies. In the remaining quarter, the co-twin survives, but can sustain major damage to the brain and other organs because of the acute loss of blood. Long term major disabilities such as cerebral palsy and major developmental delay may occur.

What are the treatment options for TTTS?

The treatment options that have been used include the following.

Expectant management or observation

In this option, the pregnancy is monitored with ultrasound examinations. Medications have been tried to reduce the amount of fluid that is produced, or to try to improve the contractions of the twins’ hearts. Unfortunately, these medical options have not been successful in treating babies with TTTS and expectant management is associated with pregnancy loss rate of more than 90%.

Serial amniocenteses/ Amnioreduction
(drainage of amniotic fluid from the sac of the recipient twin)

The aim of this treatment is to reduce the risk of preterm birth from over-distension of the uterus. An amniocentesis needle is inserted into the sac around the recipient twin and fluid is removed until there is a normal amount around the twin. Usually one to three litres of amniotic fluid may be removed and this may need to be repeated every few days or weeks. While there is a small procedure-related risk of rupture of the membranes and preterm delivery, it does appear usually effective in allowing the pregnancy to continue. Unfortunately, it does not treat the underlying pathology—the transfusion of blood via the vascular connections in the placenta.

This has been the most widely used treatment in most Fetal Medicine Centres around the world, including our own. Results from several large international registries, (including one in Australia) as well as figures from our own Centre have shown that only about 60% of babies will survive. Of major concern is the finding that 20-25% of the survivors may have subsequent neurological complications or cerebral palsy.

Septostomy

When the donor twin has no amniotic fluid around it, the membranes are wrapped tightly around it. Septostomy is where a needle is inserted into the uterus to deliberately make a hole in the amniotic membrane to allow fluid to get into the donor twin’s sac from the recipient twin. The aim is to try to equalise the amounts of fluid between the twins. Currently, there is little evidence to suggest that this is more effective than amnioreduction, and other complications can occur as a result of this procedure. We do not offer this procedure at Mater Centre for Maternal Fetal Medicine.

Umbilical cord occlusion
(not offered at Mater Centre for Maternal Fetal Medicine)

If severe, TTTS is complicated by the death of one of the twins in the womb and the transfusion process will eventually stop. If the other twin survives, it has been observed that the amniotic fluid volume returns to normal and the pregnancy often continues. However, as previously described, during the death of one of the twins, there can be further severe transfusion of blood, which could cause loss or severe damage to the co-twin.

In severe cases of TTTS, one of the twins may become extremely sick, and can be at high risk of dying swiftly. If the twins are sufficiently mature by this stage, they should be delivered. If they are not, some doctors may suggest occluding the cord of the sick twin to protect the second twin from the consequences of a severe transfusion when the sick twin dies. Cord occlusion can be done by passing an instrument into the uterus and either heat coagulating, or tying off the cord of the sick twin with a suture. This interrupts the vascular communication between the twins and allows the remaining twin to progress on its own.

While this protects the second twin, it obviously causes the immediate loss of the sick twin. (The demised twin remains in the amniotic cavity and its amniotic fluid is slowly reabsorbed with time.) Mater Centre for Maternal Fetal Medicine offers an alternative (and definitive treatment) even in this desperate condition: laser coagulation of the connecting blood vessels. We believe that this is a better option as it maximises the chance of survival for both twins despite the difficult circumstances. Our experience in the last few years showed that many even desperately sick fetuses can recover after laser surgery. Unless there is good evidence that the sick twin has already suffered from irreversible (brain) damage, we do not believe that it is necessary to give up on the fetus easily.

Fetal laser surgery

TTTS occurs as a result of transfusion of blood via vascular connections on the surface of the placenta. Over the past 10 years, a new treatment option has been developed. By passing a small fetoscope into the uterus and identifying the connecting vessels on the surface of the placenta, laser surgery can be delivered by a fibre to coagulate these connections and stop the process of TTTS. When this method was first developed, there were some arguments as to whether this should be the preferred treatment for TTTS or not. In some of the earlier studies the overall survival of babies following laser surgery appears to be similar to that of amnioreduction. Even so, it has been reported that the long term outcomes and incidence of cerebral palsy appears to be much less for laser surgery (about 5-10%) when compared with amnioreduction (15-25%). The other advantages of this procedure are that even if one of the unborn babies die, the other twin is less likely to be harmed, as there are no longer vascular communications between the babies. It was also recognised that the main advantage of laser therapy over serial amniocentesis is that it does address the underlying cause of TTTS and usually requires only one intervention.

A landmark study was published in 2004 in the prestigious New England Journal of Medicine. In this study women with TTTS were randomly assigned to treatment by either amnioreduction or fetoscopic laser surgery. This showed that survival chances for babies treated by laser surgery are significantly better than those treated with amnioreduction. Randomised controlled trials are considered the Gold Standard for evaluation of any new interventions in medicine. This landmark paper has thus established the role for fetoscopic laser surgery for TTTS.

Until 2002, this procedure has only been available in a few centres overseas. Mater Centre for Maternal Fetal Medicine is the first centre in the Asia Pacific Region to set up this service. With the assistance of Professor Ruben Quintero from Florida, USA (a world renowned fetoscopic expert), we have successfully started the program at Mater since the beginning of 2002. The vital key to success is in meticulous selection of the vessels for coagulation to interrupt the communication between the twins. Vessels not contributing to the communication process need to be spared to maximise the chance of survival of both twins. There is thus a learning curve in these procedures. By tele-linking to Professor Quintero’s site in USA and observing his operations over an eighteen month period, Mater clinicians have significantly shortened our learning curve. We had performed over 70 procedures by December 2005 (the largest series in Australia) and our results are amongst the best in the world. We have recently presented our results in national and international conferences, and have been awarded the best clinical research award by the Australasian Society of Ultrasound in Medicine, 2005. Click here to view abstract.

Our Results so far (2002 to 2005)

Since 2002, we have performed 70 laser procedures for severe cases of TTTS.

Our results on the first 50 of the 53 pregnancies that have delivered have been analysed:

The overall survival was 84 out of 100 babies (84%). In 92% of cases, at least one of the babies survived (46 out of 50 pregnancies) and in 76%, both babies survived (38 out of 50 pregnancies). These results of fetoscopic laser surgery are significantly better than most of the earlier published series in the literature. View the abstract for more information.

We also compared the results of our first 31 laser procedures with patients that were managed in our unit by amnioreduction before laser surgery was available. The overall chance of survival is significantly better (77.4% versus 59.3%). The babies are delivered at much later gestation (34 weeks versus 28 weeks), have significantly heavier birth weights, less complications after birth, and shorter length of stay in the neonatal unit. While we do not have a large enough dataset to establish our long term neurological follow-up results yet, preliminary data suggest that our handicap rates are similar to those reported in the literature: about five-10%.

Our service is available to public or private patients, Australia and overseas.

Contact details

Please feel free to contact one of our staff for any further details:

Barbara Soong

Clinical Midwifery Consultant
Mater Mothers' Hospital
Phone: +61 7 3163 8111 (pager 0894) between 9am and 5.30pm, Monday to Friday
Fax: +61 7 3163 1890
Email: Barbara.Soong@mater.org.au

Dr Glenn Gardener

Acting Director, Maternal Fetal Medicine
Mater Mothers' Hospital
Phone: +61 7 3163 8111 (pager 492)
Fax: +61 7 3163 1949
Email: Glenn.Gardener@mater.org.au

Assoc Professor Robert Cincotta

Staff Specialist, Maternal Fetal Medicine
Mater Mothers' Hospital
Phone: +61 7 3163 8111 (pager 346)
Fax: +61 7 3163 1949
Email: Robert.Cincotta@mater.org.au

Dr Greg Duncombe

Dr Shell Fean Wong

Or leave a message for Barbara by contacting Mater Centre for Maternal Fetal Medicine on +61 7 3163 1896.

References

Cincotta RB, Gray PH, Phythian G, Rogers YM, Chan FY. Long term outcome of twin-twin transfusion syndrome. Arch Dis Child Fetal Neonatal Ed 2000. 83(3): p171-6

Quintero RA, Dickinson JE, Morales WJ, Bornick PW, Bermúdez C, Cincotta R, Chan FY, Allen MH. Stage-based treatment of twin-twin transfusion syndrome. Am J Obstet Gynecol 2003. 188:p1333-1340

Banek C, Hecher K, Hackeloer B, Bertmann P. Long term neurodevolopmental outcome after intrauterine laser treatment for severe twin twin transfusion syndrome. Am J Obstet Gynecol 2003. 188:p876-880

Duncombe GJ, Dickinson JE, Evans SF. Perinatal characteristics and outcomes of pregnancies complicated by twin-twin transfusion syndrome. Obstet Gynecol 2003. Jun; 101(6):p1190-6

Senat M, Deprest J, Boulvain M, Paupe A, Winer N, Ville Y. Endoscopic laser surgery versus serial amnioreduction for severe twin-to-twin transfusion syndrome.The N Engl J Med 2004. 351:p136-44

Chan FY, Cincotta RB, Soong B, Bornick P, Allen M, Quintero R. Learning Curve for fetoscopic laser surgery can be shortened. Ultrasound in Obstet Gynecol 2005. 26(4):p360-1

Gray PH, Cincotta RB, Chan FY, Soong B. Perinatal Outcomes for severe twin-twin transfusion syndrome managed by laser ablation of placental vessels. Ultrasound in Obstet Gynecol 2005. 26(4):p437-8