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Objective To assess the clinical effectiveness of endoscopic laser coagulation of placental vessels in the
Design Prospective study.
Setting Three referral centres for the management of twin-to-twin transfusion syndrome.
Population One hundred and thirty-two pregnancies complicated by severe twin-to-twin transfusion syndrome, reflected by polyhydramnios and enlarged bladder of one twin and oligoanhydramnios and collapsed bladder of the other twin, presenting before 28 weeks of gestation.
Methods Prospective collection of data on pre-procedure assessment, the procedure and the follow up were collected prospectively. Laser coagulation of placental vessels crossing the intertwine membrane on the chorionic surface under sono-endoscopic guidance, followed by amniodrainage.
Main outcome measures Maternal and pregnancy complications, perinatal death and morbidity were assessed over the last five years with follow up of survivors.
Results Endoscopic laser was carried out at a median gestation of 21 weeks. The total number of surviving infants was 144 (55%) and there was at least one survivor in 97 cases (73%). At a minimum age of one year neurological handicap was suspected in six survivors (4.2%).
Conclusions The results of this multicentre study are similar to those in our original report on the first 45 cases. In comparison with serial amniodrainage, the survival rate may be similar, but the handicap rate in survivors appears much lower. This study stresses the need for a prospective study comparing treatment of severe transfusion syndrome threse two techniques.
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Sono-endoscopic laser coagulation was carried out in 132 pregnancies complicated by severe twin-to-twin transfusion syndrome with severe polyhydramnios during the second trimester of pregnancy, between 1992 and 1996. The women were managed in one of three centres by members of the original team who developed this technique11. The subsequent obstetric care was undertaken in the referring hospital.
In all cases, ultrasound examination demonstrated the characteristic features of twin-to-twin transfusion syndrome: same sex fetuses, single placental mass, thin intertwin membrane, polyhydramnios surrounding the recipient fetus whose bladder was enlarged, oligoanhydramnios around the smaller donor fetus whose bladder was collapsed.
The women were counselled with regard to the reported outcome in terms of number of survivors and risk of handicap associated with three available options of management: 10% and 30%, respectively, for expectant management4,6, 30% to 80% and 30%, respectively, for amniodrainage4,6,12–15 and 55% and 5% respectively for endoscopic surgery11. Termination of pregnancy was also presented as a possible option before 22 weeks of gestation although never requested as a first therapeutic option. Informed consent was obtained before the procedure. The study was approved by the respective local Ethics Committees. The results of the first 45 patients have already been reported11.
Laser coagulation of the communicating placental vessels
Detailed ultrasound examination was first performed to localise the placenta, the inter-twin amniotic membrane, the placental insertion of the umbilical cords and to ascertain any fetal anomalies. Umbilical artery Doppler was carried out to determine the presence or absence of end-diastolic flow. The appropriate site of entry on the maternal abdomen was chosen to avoid injury to the placenta or the fetuses and to allow access through the recipient sac to the inter-twin membrane, ideally perpendicular to the long axis of the donor fetus (Fig. 1).
Tocolytic therapy (indomethacin or diclofenac per rectum or salbutamol intravenously) and antibiotics (a third generation cephalosporin intravenously) were given for prophylaxis. Local anaesthetic (1 % lignocaine) was injected into the maternal abdomen down to the myometrium. Under continuous ultrasound visualisation, a rigid 2mm diameter 0° paediatric cystoscope (Olympus, Hamburg, Germany or Storz, Tuttlingen, Germany) housed in a 9.8 Charriere cannula was introduced transabdominally into the amniotic cavity of the recipient twin. A 400 pm diameter Nd:YAG laser fibre (Dornier, Munich, Germany) was then passed down the side-arm of the cannula to 1 cm beyond the tip of the fetoscope. A combination of ultrasonographic and direct vision was used to examine systematically the chorionic plate along the whole length of the inter-twin membrane to identify the crossing vessels, which were coagulated using an output of 30 to 50 watts for one to three seconds from a distance of about 1 cm16. Subsequently, amniotic fluid was drained through the endoscope cannula over a period of 10 to 15 minutes to obtain a subjective normalisation of the amniotic fluid volume on ultrasonographic examination. The women remained in hospital for 6 to 48 hours for observation.
Demographic characteristics, ultrasound findings and details on the endoscopic surgery or any further procedures were kept on a computerised database. Data on maternal and neonatal outcomes were obtained from the referring physicians and paediatricians involved in the follow up of the infants. Pregnancy outcome was examined in relation to the gestational age at presentation, previous amniodrainages, placental position, inter twin difference in size, presence or absence of fetal hydrops, umbilical artery Doppler study results, operative difficulties or complications and post-operative interventions. Analysis of variance, χ2 and Student's test were carried out to determine the significance of differences between groups.
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This multicentre study confirms the feasibility of an endoscopic technique for the coagulation of anastomotic placental vessels and interruption of the twin-to-twin transfusion syndrome. Irrespective of the vascular nature of the anastomoses or their depth within the placenta, their afferent and efferent branches are superficial and can be seen on the chorionic surface of the placenta7,17. Although the intertwin membrane does not necessarily overlie these common cotyledons, the systematic coagulation of all crossing vessels should inevitably include the branches of these anastomoses. A preliminary report I suggested that this treatment may be associated with a higher survival rate and a lower perinatal morbidity compared with treatment based on serial drainage of amniotic fluid4,6,8,13–15.
With endoscopic surgery, survival both with time and in different centres remains stable at 55% for fetuses and more than 70% for pregnancies with at least one survivor. In contrast, with the alternative method of treatment, serial amniodrainage, there are marked differences in reported results from different series. As reported by Saunders et al.4, in a series before 199 1 the survival was 30% to 40%, whereas in the last six years, using apparently the same technique the survival improved up to 83%6. Thus, three centres in five different papers6,12–15 have reported that in a total of 53 pregnancies treated with serial amniodrainage and in 14 managed with watchful waiting, the fetal survival rates were 76% and 36%, respectively, suggesting that the condition was milder than in previous studies. Also of importance, the largest series included six dichorionic pregnancies12,15. The most recent publication on serial amniodrainage reported the treatment of 26 pregnancies and the survival rate was 57%8.
An important issue in the management of severe twin-to-twin transfusion syndrome is the rate of severe handicap in survivors. With endoscopic laser the rate of neurological handicap is < 5% which is much lower than in pregnancies treated with serial amniodrainage. Thus, Pinette et al.6 reported cerebral palsy in 36% of their survivors, Bajoria et al.7 noted the presence of porencephalic cyst in 29% and cardiac dysfunction in another 29% of their 14 survivors and Trespidi et al.8 reported severe handicap in 15% of their survivors. The main underlying mechanism of perinatal handicap in twin-to-twin transfusion syndrome is thought to be an acute haemodynamic imbalance between the twins, following a hypotensive period or fetal demise, leading to an acute and significant transfer of blood from the normotensive to the hypotensive or dead fetus. This continues until the transfusing twin's mean arterial pressure equals the transfused twin's systemic filling pressure. In two series including a total of 32 monochorionic diamniotic pregnancies with death of one fetus, 17 (53%) of the surviving co-twin were handicaped.18,19.
Attempts to model the inter-twin circulation in order to define high and low risk vascular patterns7,20 remain without clinical relevance because there is no clear relation between placental histological findings and morbidity in the survivors. Bejar et al.21 reported necrosis of the cerebral white matter in surviving twins from monochorionic diamniotic pregnancies. This occurred in six of seven cases with combined venovenous (VV), arterioarterial (AA) and arteriovenous (AV) anastomoses, in three of nine with combined AV and AA, in two of eight with AA, one of twelve with AV, and none with single venovenous anastomoses. In addition, no clear in vivo vascular mapping of the placenta has yet been demonstrated to be feasible. Our attempt to coagulate all vessels crossing the inter-twin membranes is therefore the only treatment that can potentially prevent the severe haemodynamic imbalance when both twins are alive or in cases of single fetal demise.
The survival rate in the three centres involved in this study is similar to both our first report and the results of De Lia et al.22 who use a more invasive technique for introduction of the endoscope (general anaesthesia, laparotomy and hysterotomy), but a selective coagulation of suspected anastomoses. In contrast to our technique of systematic coagulation of all vessels crossing the inter-twin membrane, De Lia23 used a larger endoscope to get a more panoramic view of the placental surface and confined coagulation only to the anastomotic vessels in the vascular equator of the placenta. There are three main causes of fetal death associated with endoscopic surgery. First, miscarriage with varying contributions from the polyhydramnios of the disease and the procedure itself. Secondly, intrauterine death, most commonly of the donor fetus. The severely growth restricted donor fetus, with features of primary placental insufficiency and hypoxia, is often subjected to the additional trauma of acute obliteration of part of its placenta as a result of coagulation of all vessels crossing the inter-twin membrane. The third cause of death, often presenting as intrauterine death of both twins, may reflect failure of endoscopic surgery to obliterate all anastomotic vessels. Since there are many anastomoses and VA anastomoses between the twins, incomplete coagulation of all vessels could hasten the demise of the fetuses by worsening the inter-twin shunting of blood.
In this study we have been able to demonstrate the development of hydrops and anaemia following endoscopic surgery and death of one fetus. Since in such cases the surviving fetus was treated by intrauterine blood transfusions, it is possible that in pregnancies complicated by death of one fetus soon after the procedure, the use of cordocentesis in the survivor with the option of blood transfusion could reduce the cases where both fetuses die.
In our series 9% had prior amniodrainages. Since this group did not have a significantly worse outcome, it could be argued that the primary method of treating severe twin-to-twin transfusion syndrome is amniodrainage and only when this fails should endoscopic surgery be considered. However, the condition of both twins is likely to worsen in the meantime. This might be reflected by the tendency towards a higher incidence of previous amniodrainage in the group of recipient twins dying in utero. This would support the hypothesis that an earlier surgical approach could have prevented the recipient's demise.
In this series there was one maternal death. Although this death was unrelated to the procedure, it highlights the fact that twin-to-twin transfusion presenting with acute polyhydramnios during the second trimester of pregnancy is a severe pregnancy complication with potential risks for the mother. The only procedure-related serious complication was intra-abdominal bleeding from the uterine puncture site that required blood transfusion. In this case amniotic membrane separation made it impossible to carry out amniodrainage as usual. Presumably, the presence of severe polyhydramnios and high intrauterine pressure prevented the closure of the puncture orifice which usually occurs by a localized contraction at the site of entry of the trocar. Another potential complication that was not observed in this series is pelvic haematoma from puncture of the lateral uterine wall vessels. Although in 43% of our cases an extensive anterior placenta necessitated a very lateral entry of the fetoscope, the uterine vessels were easily visualised by colour Doppler and were therefore avoided. Consequently, in such cases of anterior placentas we did not find it necessary, as De Lia et al.22 and Deprest et al.24 to perform laparotomy and insert the fetoscope through the fundus or the posterior wall of the uterus. The position of the placenta did not appear to be a major contributor to the success or failure of the procedure.
The results presented have been stable over the last five years and the fetal survival rate compares favourably with the results presented in the most optimistic series using serial amniodrainage. Importantly, the rate of handicap among survivors appears to be much lower with endoscopic surgery. Nevertheless, the only accepted way of comparing endoscopic treatment with serial amniodrainage is a randomised study. On the basis of our results and an average of those of the recent series on serial amniodrainage6–8,12–15, a randomized controlled trial to demonstrate significant difference in survival between the two methods (Power go%), it would require a minimum of 162 women. Such a number of participants would also allow to detect a difference of 25% in the rate of handicap among survivors.
We wish to thank Mr G. Barki and Storz Endoscope for their technical support in developing the instruments necessary to the procedure.