| Twin-to-twin transfusion syndrome | |
|---|---|
| Classification and external resources | |
A pair of newborn twins affected by TTTS. Both the recipient (left) and donor (right) survived. |
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| ICD-10 | O43.0, P02.3, P50.3 |
| ICD-9 | 762.3 , 772.0 |
| DiseasesDB | 32064 |
| eMedicine | med/3410 |
| MeSH | D005330 |
Twin-to-twin transfusion syndrome (TTTS, also known as Feto-Fetal Transfusion Syndrome (FFTS) and Twin Oligohydramnios-Polyhydramnios Sequence (TOPS)) is a complication of disproportionate blood supply, resulting in high morbidity and mortality. It can affect monochorionic multiples, that is multiple pregnancies where two or more fetuses share a chorion and hence a single placenta. Severe TTTS has a 60–100% mortality rate.[1]
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TTTS occurs in approximately 5.5–17.5% of all monochorionic pregnancies.[2] Based on 2003 CDC data, the theoretical incidence of TTTS would be 1.38 to 1.86 cases in every 1,000 live births or an estimated near 7,500 cases each year in the United States. One Australian study, however, noted an occurrence of only 1 in 4,170 pregnancies or 1 in 58 twin gestations. This distinction could be party explained by the "hidden mortality" associated with MC multifetal pregnancies--instances lost due to premature rupture of membrane (PROM) or intrauterine fetal demise before a thorough diagnosis of TTTS can be made.[3]
As a result of sharing a single placenta, the blood supplies of monochorionic twin fetuses can become connected, so that they share blood circulation: although each fetus uses its own portion of the placenta, the connecting blood vessels within the placenta allow blood to pass from one twin to the other. Depending on the number, type and direction of the interconnecting blood vessels (anastomoses), blood can be transferred disproportionately from one twin (the "donor") to the other (the "recipient"). The transfusion causes the donor twin to have decreased blood volume, retarding the donor's development and growth, and also decreased urinary output, leading to a lower than normal level of amniotic fluid (becoming oligohydramnios). The blood volume of the recipient twin is increased, which can strain the fetus's heart and eventually lead to heart failure, and also higher than normal urinary output, which can lead to excess amniotic fluid (becoming polyhydramnios).
In early pregnancy (before 26 weeks), TTTS can cause both fetuses to die, or lead to severe disabilities. If TTTS develops after 26 weeks, the babies can usually be delivered alive and have a greater chance of survival without disability.
Other than requiring a monochorionic-diamniotic twin (or higher multiple) pregnancy, the causes of TTTS are not known. It is not known to be hereditary or genetic.
Some doctors recommend complete bed-rest for the mother coupled with massive intakes of protein (generally in the form of "protein shakes" such as Boost or Ensure) as a therapy to try to counteract the syndrome. Theories for why this would be effective vary, but some doctors claim to have seen it help. There are, however, no formal clinical trials indicating that the bed rest / high-protein diet is effective.
Research into TTTS is ongoing and best medical practices change quickly with respect to this condition. For the most up-to-date information, consult with a maternal-fetal medicine specialist.
There are a number of different therapies used to treat TTTS, with varying rates of success. The oldest, most traditional treatment is through serial amniocentesis, which involves periodically draining amniotic fluid from around the recipient twin in an effort to reduce the pressure of the amniotic fluid. Because serial amniocentesis increases the risk of premature delivery, it has limited success when performed early in pregnancy, especially before fetal viability. TTTS can also be treated by surgery during pregnancy, using fetoscopy, pioneered by Kypros Nicolaides, to find the interconnecting blood vessels, and a laser beam to coagulate the blood in these vessels, blocking them. This is called fetoscopic laser ablation, and is only performed in a few hospitals worldwide. Outcomes vary widely from case to case, but as of this writing statistics of fetoscopic laser ablation indicate a 90% chance that at least one twin will survive and 70% for both.[4]
Treatments practiced worldwide currently include the following.[2] They can be placed in three different categories: Non-treatment, treatment through adjustment of amniotic fluid, and treatment through adjustment of blood supply:
Non-Treatment
Expectant Management
This is equivalent of zero intervention. It has been associated with almost 100% mortality rate of one or all fetuses. Exceptions to this include patients that are still in Stage 1 TTTS and are past 22 weeks gestation.
Treatment through adjustment of amniotic fluid
Serial Amniocentesis
This procedure involves removal of amniotic fluid periodically throughout the pregnancy under the assumption that the extra fluid in the recipient twin can cause preterm labor, perinatal mortality, or tissue damage. In the case that the fluid does not reaccumulate, the reduction of amniotic fluid stabilizes the pregnancy. Otherwise the treatment is repeated as necessary. There is no standard procedure for how much fluid is removed each time. There is a danger that if too much fluid is removed, the recipient twin could die. This procedure is associated with a 66% survival rate of at least one fetus, with a 15% chance of cerebral palsy and average delivery occurring at 29 weeks gestation.
Septostomy, or Iatrogenic Disruption of the Dividing Membrane
This procedure involves the tearing of the dividing membrane between fetuses such that the amniotic fluid of both twins mixes under the assumption that pressure is different in either amniotic sac and that its equilibration will ameliorate progression of the disease. It has not been proven that pressures are different in either amniotic sac. Use of this procedure can preclude use of other procedures as well as make difficult the monitoring of disease progression. In addition, tearing the dividing membrane has contributed to cord entanglement and demise of fetuses through physical complications.
Treatment through adjustment of blood supply
Laser Therapy
This procedure involves endoscopic surgery using laser to interrupt the vessels that allow exchange of blood between fetuses under the assumption that the unequal sharing of blood through these vascular communications leads to unequal levels of amniotic fluid. Each fetus remains connected to its primary source of blood and nutrition, the placenta, through the umbilical cord. This procedure is conducted once, with the exception of all vessels not having been found. The use of endoscopic instruments allows for short recovery time. This procedure has been associated with 85% survival rate of at least one fetus, with a 5% risk of cerebral palsy and average delivery occurring at 33–39 weeks' gestation.
Umbilical Cord Occlusion
This procedure involves the ligation or otherwise occlusion of the umbilical cord to interrupt the exchange of blood between the fetuses. The procedure is typically offered in cases where one of the fetuses is presumed moribund and endangering the life or health of the other twin through resultant hypotension. Use of this treatment has decreased as TTTS is identified and treated in earlier stages and with better outcomes. When used, it is associated with an 85% survival rate of the remaining fetus(es) with 5% risk of cerebral palsy and a 33–39 weeks of gestation at delivery.
TTTS was first described by a German obstetrician, Friedrich Schatz, in 1875. Once defined by neonatal parameters—differences in birth weight and cord hemoglobin at the time of delivery—TTTS is now defined differently. Today, it is known that discordant fetal weights will most likely be a late manifestation, and fetal hemoglobin through cordocentesis is often equivalent in the twin pair even in severe TTTS.[3]
A painting known as the De Wikkellkinderen (The Swaddled Children), from 1617, is thought to represent a depiction of TTTS.[5] The drawing shows twins that appear to be identical, but one is pale (possibly anemic), while the other is red (possibly polycythemic). Analysis of the family histories of the owners of the painting suggests that the twins did not survive to adulthood, although whether that is due to TTTS is uncertain.
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