Twin to twin transfusion syndrome (TTTS) is a disease of the placenta (or afterbirth) that affects identical twin pregnancies. TTTS affects identical twins (or higher multiple gestations), who share a common monochorionic placenta. The shared placenta contains abnormal blood vessels, which connect the umbilical cords and circulations of the twins.
Depending on the number, type and direction of the connecting vessels, blood can be transfused disproportionately from one twin (the donor) to the other twin (the recipient). The transfusion causes the donor twin to have decreased blood volume. This in turn leads to slower than normal growth than its co-twin, and poor urinary output causing little to no amniotic fluid or oligohydramnios (the source of most of the amniotic fluid is urine from the baby). The recipient twin becomes overloaded with blood. This excess blood puts a strain on this baby’s heart to the point that it may develop heart failure, and also causes this baby to have too much amniotic fluid (polyhydramnios) from a greater than normal production of urine.
TTTS can occur at any time during pregnancy, even while a mother is in labor at term. The placental abnormalities determine when and to what degree a transfusion occurs between the twins. Chronic TTTS describes those cases that appear early in pregnancy (12-26 weeks’ gestation). These cases are the most serious because the babies are immature and cannot be delivered. In addition, the twins will have a longer time during their development in the womb to be affected by the TTTS abnormalities. Without treatment, most of these babies would not survive and of the survivors, most would have handicaps or birth defects. Acute TTTS describes those cases that occur suddenly, whenever there is a major difference in the blood pressures between the twins.
This may occur in labor at term, or during the last third of pregnancy whenever one twin becomes gravely ill or even passes away as a result of the abnormalities in their shared placenta. Acute TTTS twins may have a better chance to survive based on their gestational age, but may have a greater chance of surviving with handicaps.
As the Founder of The TTTS Foundation, I want you to know we are here for you. Being told that you are carrying twins or triplets is truly an exciting and blessed moment. Even with this diagnosis, there is considerable hope for your babies. We will help you. You are not alone.
The type of placenta nurturing identical twins plays a significant role in the development of complications in multiple gestation. Identical twins may either have their own separate placentas or they may share a common placenta. The impetus for and the timing of the embryo to split into identical twins is unknown, but the later this occurs the more complications are seen.
Based on 2005, similar to 2018, USA National Center for Health Statistics (4,138,349 total births), the rate of multiple births per year is now 1:30 (3.4%), or approximately 139,816 twins or higher multiples.
The majority of identical twins share a common (monochorionic) placenta, and of these approximately 15% go on to develop TTTS.
By extrapolating the number of expected identical twins (about one-third) from annual multiple births, and the number of twins with monochorionic placentas (about two-thirds), and from these the number thought to develop TTTS (about 15%), there are at least 4,500 TTTS cases per year in the U.S. alone:
139,816 X .33 X .66 X .15 = 4,568 cases of TTTS per year in U.S. (involving 9,500 or more babies)
Since spontaneous pregnancy loss (spontaneous abortion) and pregnancy terminations (elective abortions) that occur prior to 20 weeks go uncounted by the C.D.C., our estimate of TTTS cases may be very conservative.
Although infertility treatments have increased the rate of multiple birth, they have not diluted the expected incidence of identical twins even though multiple embryos are often produced and implanted. Studies show a higher rate of identical twins (up to 20 times with IVF) in women having these treatments than occur naturally.
The tragedy of TTTS is that there are two babies (at least) who begin the pregnancy healthy, without genetic defects, who suffer consequences related to their placenta type.
The historic twin survival rate with chronic TTTS was less than 10% before doctors could make the diagnosis in the womb by ultrasound. With the introduction of ultrasound (in 1980), the survival odds greatly improved because treatment of the TTTS was now made possible while the mother was still pregnant (see Warning Signs for the babies below).
The excess amniotic fluid (polyhydramnios) would cause over distention of the uterus, and pregnancy loss occurred when the mother went into premature labor or the baby’s bag of water broke.
In some circumstances the recipient twin my pass away (from heart failure due to the excess blood), or in other cases the donor (from the loss of blood or having a placental share too small to receive the necessary nutrients).
This sometimes made the situation better for the other twin, but in half of the cases the other twin also passed away or survived with severe birth defects.
It is crucial for parents with a multiple gestation to determine their placental type early. With monochorionic twins, you should watch carefully for the warning signs listed above. Since TTTS is a high-risk problem that can happen quickly and at any time in pregnancy, frequent examinations and ultrasound scans are necessary to catch the problem early. It is critical that physicians be aware of the warning signs.
The Foundation strongly advocates weekly ultrasounds with a perinatolgist from 14 weeks gestation through delivery to look for placental share problems and TTTS as well as asking The TTTS Foundation’s 15 Most Important Questions.
Gestation Age at Diagnosis: Prior to 25 weeks is more serious because the babies cannot be delivered at this time, and they will be exposed to the syndrome longer. Most calls to the Foundation are from couples at eighteen weeks’ gestation.
Gestational Age at Delivery: At 28 weeks and beyond, or with an estimated birth weight of 1500gm (3lbs. 5oz.) or more, doctors become more optimistic regarding the outcome for the twins with delivery. In TTTS, the doctors are often faced with the question, ‘Are the babies better off out than in?’ as they trade off the risks of early delivery versus continuing a TTTS pregnancy.
Degree of Growth Discordance: This implies that the babies are found to be different sizes on the ultrasound scan. A difference of over 20% is though significant, but this depends on gestational age that the difference appears (sometimes the difference is given in weeks rather than a percentage). The twin’s size difference may be due to either the transfusion of nutrients or unequal sharing of the common placenta or both.
Degree of Discordance in Amniotic Fluid: The recipient may have quarts of excess amniotic fluid (polyhydramnios) and its bladder always appears full on ultrasound scan. The donor may produce so little urine that its amniotic sac may be empty (oligohydramnios) and the baby’s bladder impossible to see with ultrasound.
Presence of Hydrops in One Twin: Hydrops implies fluid buildup in the baby’s skin and body cavities, and is usually due to heart failure. It can be seen on ultrasound, and it usually involves the recipient twin who is overwhelmed with too much blood.
TTTS outcomes are ultimately determined by the number and type of connecting blood vessels, and the way the twins share the placenta (which both occur randomly). Since no two placentas are the same, the outcome is always hard to predict.
Regardless of the therapy chosen, the majority of TTTS survive and majority of survivors will be normal. However, the various treatments available do differ in their outcomes: the number of survivors, the number of healthy survivors, and the ability to prolong pregnancy (see Treatments below and the section containing Medical Research and Articles).
The majority of TTTS twins, with and without treatment, will be born prematurely and need to spend some time in the newborn intensive care unit.
Once diagnosed, it is possible to move through all 5 stages within 24 hours. It is more likely, however, that you will experience a chronic, over time, experience with TTTS and have time to have the treatments.
The TTTS Foundation feels strongly that all mothers should begin horizontal rest and the nutritional supplements discussed in the site from the research of Dr. Julian De Lia, The TTTS Foundation Medical Advisory Member and Board of Directors who pioneered the laser surgery.
Further treatments are available based on the symptoms of the babies. Placental share and cord insertion issues are crucial to understand when making decisions about treatments as sometimes not having the surgery is in their best interest.
Family and friends can be a very important source of comfort and strength during a pregnancy diagnosed with twin to twin transfusion syndrome. It is often difficult, however, to have time to devote yourself to explaining the disease to them. If you would like a packet mailed to anyone in your family, for example, the babies’ grandparents or close friends, please call, or have them call the Foundation at 440-899-8887 and we will mail this to them and talk with them on the phone. If you are in the hospital, you may also call toll-free at 800-815-9211.
Family and friends need to know that twin to twin transfusion syndrome is not hereditary or genetic. The babies are completely normal and healthy babies, but they are at risk for problems because of the disease in their shared placenta. Twin to twin transfusion syndrome is completely random and it is not something that was caused by something the parents did or did not do. It is also not something that the babies are doing to each other. Everyone is an innocent bystander.
These are often first concerns of families. Sometimes family and friends say terrible things to parents not realizing they are ultimately blaming them for the problem. Going over these basic facts listed above can be helpful in ending hurtful comments.
Family and friends can best give support to the diagnosed parents by letting them know that they and their babies are loved and are being prayed for (look at the section on ‘quotes’). Sometimes nothing needs to be said. Just having them hold the parent’s hand and letting them cry, or letting them be hopeful and encouraged, is more meaningful then words could ever be.
Friends and family can help simply by explaining to the parents that they don’t understand completely what they are going through or what they need. Parents can tell them how they can help by saying, “If you love me, then please trust me, that this is what I need from you.” This will help make family and friends feel that the door is open for their involvement and they will be more then happy to do what the parents have said.
Ways that family and friends can help diagnosed parents include: helping with other children, providing meals and housecleaning, driving to appointments, helping shop for the babies, bringing magazines to read while the mom is on bedrest, making a cooler of food by the mom’s bedside, making gifts for the babies, buying things to make for the babies like needlepoint projects, searching the Internet for more information, bringing books from the library, and letting the parents know their babies are very important and worth fighting for.
When we go through difficult times in our lives, we realize what life is truly about. It is about our family and friends. It is about our children and being parents to them and loving them. Encourage the parents to try to surround themselves with people who bring comfort and peace.
Have them separate from those who add stress, who are not willing to try to understand, and who cause emotional pain. Those that truly love the parents and are close with them will always be there for them no matter what. We always remind them that God is with them. They are never alone.
