Mamas on Bedrest: When Twins Share Too Much-TTTSJanuary 18th, 2012
About a week ago one of my mamas on bed rest called to give me an update on her condition. She’s carrying twins and after several weeks of grizzly hyperemsis gravidarum, things have finally settled down-or so she thought. Now at 25 weeks, she is having a Level II Ultrasound to evaluate whether or not her twins have Twin To Twin Transfusion Syndrome or TTTS.
What is Twin to Twin Transfusion Syndrome (TTTS)?
TTTS is a very specific condition that occurs in twins under very specific conditions. According to the Texas Children’s Hospital,
In two-thirds of identical twins, each twin has its own amniotic sac but shares a common placenta. This type of monozygotic (identical) twinning is called monochorionic, diamniotic since there is an inner layer surrounding the amniotic sac of each twin, but there is only one common outer layer (chorion) surrounding both of the sacs.
TTTS occurs in monochorionic, diamniotic twins. In almost all of these pregnancies, the single placenta contains blood vessel connections between the twins. For reasons that are not clear, in 15 percent to 20 percent of monochorionic, diamniotic twins, the blood flow through these blood vessel connections becomes unbalanced, resulting in a condition known as twin-twin transfusion syndrome (TTTS).
In TTTS, the smaller twin (often called the donor twin) does not get enough blood while the larger twin (often called the recipient twin) becomes overloaded with too much blood. In an attempt to reduce its blood volume, the recipient twin will increase the urine it makes. This will eventually result in the twin having a very large bladder on ultrasound, as well as too much amniotic fluid around this twin. At the same time, the donor twin will produce less than the usual amount of urine. The amniotic fluid around the donor twin will become very low or absent.
In some severe cases of TTTS, Twin Reversed Arterial Perfusion (TRAP) sequence occurs. TRAP sequence or acardiac twinning is a very rare problem, occurring in approximately 1% of twins sharing one placenta. One twin is usually structurally completely normal. The other is an abnormal mass of tissue, consisting usually of legs and a lower body, but no upper body, head or heart. Because of the absent heart, the term “acardiac twin” is used to describe this mass. The normal fetus is referred to as the “pump twin” because its heart is used to pump blood to the abnormal mass. The “acardiac twin” has no chance of survival.
When I realized what my mama would be facing, I had to share it here. While the vast majority of twin pregnancies proceed with few complications, i.e. each twin has its own placenta and sac, its a staunch reminder that multiple pregnancies carry their own inherent risks. While Mother Nature in her marvelous wisdom allows for these wondrous births, sometimes things don’t proceed as planned.
Diagnosis and Evaluation of TTTS
So how would a mama know if her babies were having TTTS? Many times mama has no idea at all. Then when she has an ultrasound, the imbalance in amniotic sacs is noted, there is growth retardation in one baby or develpmental abnormalities in one twin. On occasion, mama may notice that she is increasing in girth quickly. This often happens when the “recipient” twin in TTTS is putting out too much urine in an attempt to normalize its fluid volume, so mama’s belly is getting larger more quickly. The Diagnosis of TTTS is made via ultrasound and the severity is determined by the timing in the pregnancy (the earlier it is detected, the more severe it tends to be), the development of the fetuses and the status of the amniotic sacs and placentas. To better determine the severity of TTTS in the twins, doctors at the UCSF Fetal Treatment Center also evaluate the babies hearts via echocardiogram, their kidneys, bladders and arterial blood flow via the umbilical cords.
Treatments for TTTS
Amnioreduction. Amnioreduction is a minimally invasive treatment in which some of the excess amniotic fluid produced by the recipient twin is removed via amniocentesis. While this was at one time the standard treatment for TTTS, it has been replaced by laser treatments that have superior results and birth outcomes for both twins. It is still effective in some lower risk, very specific cases.
In some cases, the imbalance in amniotic fluid levels is balanced by making a small hole in the membrane separating the two fetuses, called a septosomy. With a septosomy, excess fluid from the recipient twin can flow back into the sac of the donor twin who has low amniotic fluid levels. Complications include all the complications associated with amniocentesis (infection, preterm labor and/or premature rupture of membranes), widening or complete rupture of the septosomy in which case both twins would share one sac, subsequent tangling of the fetal umbilical cords, fetal death (s).
Laser Ablation of Placental Blood Vessels
In more advanced stages of TTTS, laser ablation of the blood vessels on the placenta found to communicate between the twins are closed using laser light energy. If done at the appropriate time and on the appropriate blood vessels, Laser ablation can be a curative procedure. According to the Texas Children’s Hospital,
Laser ablation has been shown to result in the survival of at least one twin in 70 percent to 80 percent of cases and both twins in one-third of cases.Should one fetus die after the procedure, the likelihood that the surviving fetus will develop complications is reduced from 35 percent to approximately 7 percent, because the babies are no longer sharing blood vessels between them. In one-third of cases, neither twin will survive.
Selective Cord Coagulation. Unfortunately, some parents are faced with the heartbreaking decision of whether or not to end the life of one twin to save the life of the other. This decision often has to be made in cases where laser ablation is not an option and/or the survival of one twin is questionable at best. By stopping the flow in the cord of the dying twin, the other twin can is protected from any adverse events as a result of the iminent demise of its twin and be given the best chance of survival. Survival of the one remaining fetus can be expected in 85 percent of cases.
This procedure is usually reserved for TRAP sequence. In this procedure, a specialized needle is passed into the amniotic fluid and then into the body of the acardiac fetus. A special current is then applied to the needle to burn the area around the major blood vessel in the abnormal fetus. This will stop the blood flow and allow the pump twin (normal twin) to no longer have to send blood to the acardiac twin. Complications of infection, premature contractions and premature rupture of the membranes can occur as in any needle procedure. In one series, the risk for premature rupture of the membranes was 8 percent. In this same series, the chance for a successful live birth for the pump twin was 90 percent.
Truly this is overwhelming information and parents faced with TTTS face some unheard of decisions. However, in today’s technological world, there are more treatment options and more opportunities for successful live births. Hopefully, this brief and very simplistic overview of TTTS will help some parents cope with a very difficult situation and make very difficult choices.
Do you have experience with TTTS? Please share your experience with our Mamas on Bedrest in the comments section below or by sending an e-mail to [email protected].
Note: A huge thanks to Ms. Jenya Cassidy for sharing her story about TTTS. Jenya shared an invaluable resource, Dr. Julian De Lia. Dr. De Lia is pioneer in laser surgery treatment for TTTS and has also done extensive research into the nutritional needs of women with high risk pregnancy. Here is his contact information:
TWIN-TO-TWIN TRANSFUSION SYNDROME
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MILWAUKEE, WI 53210-1688