What is Twin-to-Twin Transfusion Syndrome?
Twin-to-Twin Transfusion Syndrome (TTTS) affects approximately 15% of identical twins that share a placenta. The condition occurs when blood from one twin (commonly called “the donor”) is transfused into the other twin (commonly called “the recipient”) via blood vessels in the shared placenta. It can also occur in triplet or quadruplet pregnancies in which foetuses share a placenta - the placenta image on this page is from an identical triplet pregnancy where all three boys shared the placenta: read more.
Although it only affects a small number of pregnancies (approximately 2% of twin pregnancies), it is a potentially serious condition and can have life-threatening effects on either one or both of the twins.
In the normal situation, blood vessels on the surface of a shared placenta of identical monochorionic twins connect to one another. There is a balanced amount of blood that flows in both directions. If there is a disturbance of this balance with more blood flowing from one baby (the donor) to the other (the recipient), TTTS occurs.
As the donor loses blood, the amount of urine produced by that twin decreases. This results in a drying up of the amniotic fluid around this baby. This lack of amniotic fluid is known as ‘oligohydramnios’ and sometimes the donor twin is referred to as the ‘stuck twin’. The recipient twin, on the other hand, gets too much blood and results in the recipient twin producing copious amounts of urine and rapid accumulation of fluid. This extra fluid results in a condition called ‘polyhydramnios’.
The extra blood the recipient twin receives can result in enlargement of the heart, and the heart can start to fail. The recipient twin’s body cavities may accumulate fluid and this can result in a condition called ‘hydrops’. If the recipient twin develops hydrops, its life is seriously threatened. The growth in the donor twin becomes restricted and in severe cases, this twin is in danger of dying.
TTTS will normally develop between about 16 and 28 weeks’ gestation. The mother’s abdomen may increase in size rapidly due to the extra amniotic fluid around the recipient twin. This may result in rupture of her membranes and/or premature labour.
Occasionally, one of the twins may be lost before delivery. If this happens, the vascular connections in the placenta may cause a serious risk to the surviving twin. The drop in blood pressure at the time of the death of a twin may cause an acute transfusion between the twins. However in about half of these cases, this transfusion may be small and not cause any damage to the surviving twin. In a further quarter of cases, the surviving twin may lose so much blood that it also dies. In the remaining quarter, the surviving twin sustains major damage to the brain and other organs due to the acute loss of blood. This may result in major disabilities such as cerebral palsy.
Symptoms of TTTS In the mother:
- Sudden weight gain
- Fundus appears large for dates (often will appear like a term pregnancy)
- Abdominal pain and tightness
- Premature onset of contractions
In the babies (determined by ultrasound assessment):
- Evidence of a monochorionic (shared) placenta
- Same sex twins
- Thin, hard to find, separating membrane
- One twin may be much larger than the other
- Different size bladders in each twin
- Polyhydramnios around one twin (more than 8cm pocket) and minimal amount of amniotic fluid around the other twin (less than 2cm pocket).
TTTS is diagnosed after an ultrasound is performed. Ideally, once identical twins are diagnosed, ultrasound scans should be performed at regular intervals so that if TTTS develops, treatment can begin as soon as possible.
What treatments options are currently available in Australia?
This involves draining some of the amniotic fluid from the recipient baby’s sac, hopefully reducing the risk of premature birth caused by the overstretching of the mother’s uterus. An amniocentesis needle is inserted into the recipient baby’s sac and the extra amniotic fluid is removed until a normal amount of fluid remains. This procedure may need to be repeated regularly (eg: every few days, weekly or fortnightly) and usually 1-3 litres of fluid is removed. There is a small risk of rupture of the membranes and premature delivery with this procedure. However it is seen to be one of the most effective ways of allowing the pregnancy to continue. Amnioreduction is the most widely used treatment for TTTS. However it does not treat the cause of TTTS, that is, the transfusion of blood between the babies via the placenta. About 60% of babies survive under this treatment, but 20- 25% of survivors can be affected by neurological complications including cerebral palsy.
This treatment involves inserting a needle into the uterus and piercing the separating membrane so the fluid can transfer from the recipient twin’s sac to the donor twin’s sac. The aim of this procedure is to equalise the amounts of fluid between the twins.
Umbilical cord occlusion
This treatment is only offered by some hospitals, when one twin is extremely compromised with a very real possibility of dying. If one twin dies, the drop in blood pressure causes an acute transfusion to occur between the twins. By tying off the cord of the compromised twin, this acute transfusion is unable to occur. However, the compromised twin is immediately lost.
Foetal laser surgery
This procedure is new to Australia with a limited number of tertiary referral hospitals currently performing it. A foetoscope is passed into the uterus and the connecting blood vessels in the placenta are sealed using laser. This results in the process of TTTS being halted. Although the overall survival rates by using foetal laser surgery are similar to that of amnioreduction, the risk of cerebral handicap is significantly less (10%). Laser surgery seems to be especially suitable for severe cases of TTTS (abnormal Doppler blood flow assessment, hydrops (excessive fluid accumulating in the baby) or early presentation of TTTS, whereas the survival with amnioreduction is much worse in these groups. Check with your obstetrician or hospital as to the availability of this surgery.
These options are not all available at every hospital.
This information has been provided by AMBA's Patron Assoc Prof Mark Umstad MB BS, MD, FRCOG, FRANZCOG Consultant Obstetrician, Multiple Pregnancy Clinic, Royal Women’s Hospital, Melbourne.
What support is there for families at risk of or experiencing TTTS?
AMBA clubs around Australia can provide support to families during their pregnancy - www.amba.org.au/clubfinder
AMBA's Forum has a TTTS board and useful information - www.amba.org.au/forum
Tamba (UK) have some great information and downloadable resources on their website - https://www.tamba.org.uk/ttts-resources
TTTS Australia & New Zealand - This is a Facebook group for families who have been through Twin to Twin Transfusion Syndrome (TTTS) or are currently going through TTTS in Australia or New Zealand.
TTTS Grief Support - a US based group of parents who provide care packages at no cost to families around the world.
Contacts for managing TTTS
This list has been provided by AMBA's Patron Assoc Prof Mark Umstad. Only major capital cities have the facilities and expertise to deal with TTTS complications.
1. NSW: RPA Sydney
RPA Sydney is keen to see women with complicated twin / higher order multiple pregnancies. They offer a range of services to these women including:
- Serial ultrasound management through a dedicated ‘multiple birth’ ultrasound clinic (including serial Doppler for TAPS (twin anaemia-polycythaemia sequence)/ sIUGR (intrauterine growth restriction).
- NT / cFTS (combined first trimester screening) assessment and NIPT (non-invasive prenatal testing) for aneuploidy screening
- CVS (chorionic villus sampling)/ amniocentesis
- Selective reduction (early pregnancy)
- Endoscopic laser photocoagulation of placental anastamoses in twin-twin transfusion syndrome
- Selective reduction (late pregnancy / cord occlusion)
- Management of MCDA (monochorionic diamniotic) twins / TRAP (twin reversed arterial perfusion)
The contact details for the service are:
RPA Woman and Babies / Fetal Medicine
Royal Prince Alfred Hospital
Camperdown NSW 2050
Tel: 02 9515 8887 (to Fetal Medicine secretary)
Tel: 02 9515 6111 (hospital switchboard) then page the MFM or COGU Fellow
2. WA: KEMH, Perth
King Edward Memorial Hospital in Perth, Western Australia manages the majority of complicated multiple pregnancies in the state of Western Australia and all cases of TTTS. They have a successful laser program for TTTS (plus interventions for other twin complications). They have an active interest in complicated multiple pregnancies and will see any woman with a problem.
3. Queensland: Mater Hospital, Brisbane
The best person to contact in the first instance would be the Midwifery Consultant, Barb Soong, who can direct any queries appropriately. Barb coordinates our fetal therapy service.
Alternatively Barb can be contacted directly by phone on +61 7 3163 1894 during office hours Monday to Friday.
4. Victoria: Victorian Fetal Therapy Service
All of the hospitals in Melbourne who collaborate to provide fetal therapy can be contacted via the contact page at http://vfts.com.au/html/contact.htm.
5. NSW: Fetal Therapy Service at RHW Sydney
The NSW Fetal Therapy Centre at RHW are always keen to review complex cases of monochorionic twin/multiple pregnancies.
The contact details for the Department are those below:
Clinical Fetal Medicine Enquiries:
T: (+61) 2 9382 6098
F: (+61) 2 9382 6706
Their lead midwives, Sandy and Kate, usually take faxed referrals and then we contact the clients directly. However, in many cases the clients themselves contact us directly, in which case they just require a GP referral. Their clinic is entirely within the public system.