Last Updated：17 2月. 2014
The basis for twin–twin transfusion syndrome (TTTS) may be the existence of intertwin placental vascular communications. The establishment of unbalanced blood flow from the donor twin to the recipient twin through the communicating vessels can result in profound hemodynamic disturbances in each twin. This syndrome is diagnosed by a marked difference in the volume of amniotic fluid between the twins. Especially for cases in which TTTS occurs prior to 26 weeks’ gestation, it is considered that leaving the situation untreated would result in a death rate of 90% or higher. Recently Fetoscopic Laser Photocoagulation of the placenta anastomotic vessels (hereinafter, referred to as laser surgery) has been successfully used to treat a number of infants. Laser surgery involves inserting an endoscope (fetoscope) into the mother’s uterus, and implementing coagulation therapy on the placenta anastomotic vessels between the twin fetuses using laser beams. [Please see the TTTS page]
At the same time, monochorionic twin fetuses (Selective intrauterine growth restriction: IUGR) with concomitant developmental disorders are present similarly to TTTS, but are believed to be caused by an imbalance in blood flow via anastomic vessels and, additionally, an imbalance in the area of the placenta occupied by each twin. In Japan, a survey of prognoses for cases of Selective IUGR shows that in approximately 90% of cases without abnormalities in umbilical artery blood flow, both twins survived without subsequent complications, whereas this was true in only 35% of cases with abnormal umbilical artery blood flow. In addition, only 4% of cases with normal umbilical artery blood flow showed poor prognosis (death or subsequent complications) for both twins, while 40% of cases showing an abnormal blood flow came to adverse outcome. Furthermore, cases of severe Selective IUGR, which demonstrated abnormal umbilical artery blood flow in combination with severe oligoamnios, resulted in the death of 90% or more of the smaller fetuses, and 55% of the larger fetuses. Additionally, the small proportion of smaller fetuses that survived had neurological complications. This indicates that cases with abnormalities in umbilical artery blood flow and severe oligoamnios have poor prognosis and require particular care. For cases of monochorionic twins in which one twin has died within the uterus, the blood of the surviving fetus is transferred at high speed via the anastomotic vessels into the dead fetus, which can lead to the onset of severe anemia and a state of shock. This phenomenon is dangerous as it can result in the death of the remaining fetus, or in subsequent complications.
As cases of severe Selective IUGR experience the aforementioned negative process, it is considered important to establish a treatment method. The effectiveness and safety of laser surgery with regard to severe Selective IUGR is anticipated to be similar to those for TTTS, but there is no verification data for this as of yet. Since laser surgery can shut off the blood supply between the fetuses in cases of Selective IUGR, however, it is expected not only to prevent the death of the fetus in utero, but also to facilitate the extension of pregnancy and the development of the fetus, allowing smooth progress after birth. Additionally, even if one fetus dies, it is anticipated that death and/or neurological damage can be prevented, since the procedure prevents a change in blood flow in the living fetus.
This clinical trial focuses on women who are severe Selective IUGR cases at between 20 and 25 weeks’ gestation, and involves the implementation of laser surgery with the purpose of improving the prognosis for the fetuses, as well as taking the safety of the procedure into consideration. Participating patients are required to remain in hospital for a minimum of two weeks after receiving the treatment. The trial began in January 2012 and expects to recruit 10 participants. The laser surgery is based on the laser surgical procedure currently used on TTTS patients. The surgery involves identifying the anastomotic vessels on the surface of the placenta using a fetoscope, and coagulating anastomotic vessels. If necessary, artificial amniotic fluid is introduced to the uterus in order to establish a field of vision. Once the coagulation of all anastomotic vessels has been completed, and confirmation has been given that there are no remaining anastomotic vessels, the procedure is complete. Finally, the patient is administered drugs to control uterine contractions, in order to prevent premature delivery.