Endoscopic laser coagulation in the management of severe twin-to-twin transfusion syndrome

An Experience of Laser Surgery for Feto-Fetal Transfusion Syndrome Complicated with Unexpected Feto-Fetal Hemorrhage in a Case of Monochorionic Triamniotic Triplets

Feto-fetal transfusion syndrome (FFTS) in monochorionic triplets is a rare clinical entity which may share the principal adverse perinatal outcomes of twin-twin transfusion syndrome. Recently, favorable prognoses regarding morbidity and mortality in twins after selective laser photocoagulation of placental communicating vessels (SLPCV) have been described. But descriptions of this procedure in monochorionic triplet cases are limited. This is the case report of an experience of SLPCV applied to monochorionic triamniotic triplets with FFTS. Triplet A had polyhydramnios, while absent end-diastolic flow in the umbilical artery of triplet B, the triplet with anhydramnios, was persistent. Triplet C looked normal, vertical amniotic pocket and Doppler studies yielding normal results. At the beginning of the SLPCV procedure, feto-fetal hemorrhage, subsequent to the fetal death of the donor triplet, occurred. Both surviving cofetuses showed persistent bradycardia; and 1 fetus died while the other recovered from the fetal bradycardia. All vascular anastomoses between the 3 triplets could be identified and obliterated, requiring two trocars. Our fetoscopic observation revealed feto-fetal hemorrhage after demise of monochorionic triplet, which led to injury of other fetuses due to hypovolemia in an instant. In conclusion, SLPCV might be a valid option for FFTS in triplet cases, while further experience is required in order to evaluate the risks and benefits of this procedure in triplet cases.

Combined sonographic and endoscopic umbilical cord occlusion in twin and triplet gestations

OBJECTIVE

To review our experience with a minimally invasive technique for umbilical cord occlusion as a method of selective feticide in monochorionic sets.

STUDY DESIGN

Umbilical cord occlusion was completed using 3 mm bipolar cautery under ultrasound guidance (3D/4D, n = 6; 2D, n = 6) with pre and post ligation endoscopic evaluation.

RESULTS

12 cases of monochorionic sets where selective feticide was performed were identified during the period 2000 to present. There were four triplet and eight twin gestations in the study cohort. Median interval from intervention to delivery was 16 weeks (range, 5-19). All co-twins survived the procedure and 15 of 16 were delivered after 33 weeks.

CONCLUSIONS

Umbilical cord occlusion in monochorionic sets can be accomplished in a minimally invasive manner with combined endoscopic and ultrasound guidance in both twin and triplet pregnancies.

Intrauterine hemodynamic change in TTTS: the alterations in the inferior vena cava waveform in the donor fetus

BACKGROUND

Significant hemodynamic changes are commonly observed in both fetuses in twin-twin transfusion syndrome.

METHODS AND RESULTS

We describe two donor fetus cases in twin-twin transfusion syndrome associated with abnormal waveform patterns in the inferior vena cava after therapeutic amnioreduction. Subsequent echocardiographic examinations demonstrated progressive deterioration of the cardiac function in the recipient fetuses.

CONCLUSIONS

We suggest that alterations in the inferior vena cava waveform in the donor fetuses may contribute to the accurate prediction of deterioration in fetal circulation after amnioreduction.

Twin-to-twin transfusion: update on management options and outcomes

PURPOSE OF REVIEW

The diagnosis and treatment of twin-to-twin transfusion syndrome has progressed to a staging system to allow directed therapy with the addition of laser to traditional serial amnioreduction. The management options and outcomes are reviewed here.

RECENT FINDINGS

In three observational and one randomized controlled trial, laser photocoagulation of chorionic plate vessels at the intertwin membrane improved perinatal survival of at least one fetus and reduced neurological morbidity. Cerebral palsy continues to be a major contributor to adverse outcome with rates of around 20% for survivors.

SUMMARY

Treatment strategies for this condition have remained controversial, but two main approaches have been commonly used. Serial, aggressive amnioreduction and fetoscopic laser photocoagulation of the chorionic plate vascular anastomoses at the intertwin membrane. Using the former technique, survival rates of between 18 and 83% have been described. However, 5-58% neurological morbidity has been demonstrated in the surviving infants treated by serial amnioreduction alone. Laser photocoagulation has been advocated in a few specialist centres. Such treatment has been associated with survival rates of between 55 and 69% and potentially reduced neurological morbidity of between 5 and 11% in surviving infants.

[Neurological outcome of children from twin pregnancies]

The neurological outcome is an important issue regarding twin pregnancies. In fact, twin pregnancy is clearly associated with an important neurological morbidity, roughly 4 times higher than singleton pregnancy. It is possible to distinguish some high-risk situations, making it possible to calculate more accurately the individual risk. The different aetiologies are analysed: hypotrophy, prematurity, malformations, prenatal occurrence of anoxic and ischemic lesions, and particularly the link with monochorionicity. The neurological outcome is mainly depending on hypotrophy and prematurity. However, the rate of long-term neurological complications is not different between twins and singletons after adjustment for term and birth weight. An increased risk of malformation is associated with twin pregnancies, essentially a high rate of abnormal neural tube closing (RR=2). Monochorionic pregnancies have a specific morbidity, not related to these aetiologies, with characteristic anoxic and ischemic lesions. Cerebral palsy is observed in 10-20% of the monochorionic pregnancies, vs 3.7% of the bichorionic ones. These complications are linked to the constant vascular anastomoses, between the circulations of the two monochorionic twins. When the twin-to-twin transfusion syndrome is severe, a poor neurological outcome is observed in 4 to 18% of the surviving children. However, this rate depends on studies, treatments, and methods of neurological evaluation. The laser destruction of anastomoses could decrease this morbidity. The stillbirth rate, either associated or not with twin to twin transfusion syndrome, is increased by monochorionicity. The death of one of the twins is associated with a 20% higher risk of neurological sequelae for the surviving co-twin.

Paradoxic activation of the renin-angiotensin system in twin-twin transfusion syndrome: an explanation for cardiovascular disturbances in the recipient

Despite advances in treatment, twin-to-twin transfusion syndrome (TTTS) still carries a high risk for perinatal mortality and morbidity. Simple blood transfer from the donor to the recipient twin cannot explain all of the features of this disease, in particular the recipient's hypertensive cardiomyopathy. We report a case in which TTTS resulted in preterm delivery with early neonatal death of both twins, allowing assessment of the renin angiotensin system (RAS) status of each fetus, both by cord blood renin and aldosterone assay and by renal immunohistochemistry. The donor had severe oliguria/oligohydramnios, whereas the recipient, in addition to severe polyuria/polyhydramnios, had cardiomyopathy, atrioventricular regurgitation, and ascites. Although immunohistochemistry demonstrated that renal secretion of renin was up-regulated in the donor and down-regulated in the recipient, cord blood levels of renin and aldosterone were similar, with high renin levels in both twins. This observation supports the hypothesis that despite renal RAS down-regulation, the recipient is exposed to RAS effectors elaborated in the donor and transferred via placental shunts. This may contribute to cardiomyopathy and hypertension in the recipient, which cannot be accounted for by hypervolemia alone. We thus hypothesized that in TTTS, the recipient's hypertensive cardiomyopathy could be due to a mechanism similar to the classical model of hypertension referred to as "2 kidneys-1 clip." Thus the hypovolemic donor twin, comparable to the clipped kidney, produces vasoactive hormones that compromise the recipient, comparable to the normal kidney, causing hypertension and cardiomyopathy.

Twin-twin transfusion syndrome: where do we go from here?

Management of Twin-Twin Transfusion Syndrome (TTTS) is one of the most challenging clinical problems concerning multiple gestations. The pathophysiology of TTTS and Quintero staging system are described. The importance of fetal echocardiograms in assessing prognosis and response to therapy is highlighted. Treatment modalities, particularly amnioreduction, microseptostomy, and fetoscopic laser photocoagulation, are discussed. Questions still remain as to how various treatment options affect short- and long-term cardiac and neurodevelopmental outcomes and which patients will benefit most from selective laser photocoagulation therapy.

Management of Multiple Pregnancy

Over the past 20 years, the number and rate of multiple births have dramatically increased in the United States. The rise in multiple births is mainly attributable to the increased use of ovulation-inducing drugs and the newly developed assisted reproductive technologies such as in vitro fertilization. Multifetal gestation is associated with an increased risk of perinatal morbidity and mortality. Multiple births account for an increasing percentage of low-birth-weight infants, preterm births, and infant mortality. In this article, the unique complications of multiple gestation and their management are reviewed. Also, selective termination and multifetal reduction in multiple gestation are discussed.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to describe the effects of the rising rate of multiple pregnancies on perinatal morbidity and mortality, to recall the complications of diagnosing and treating abnormalities of multiple pregnancies, to list the multiple severe complications associated with multiple gestations, and to describe the difficulty in managing these complications.

Management of Multiple Pregnancy: Prenatal Care???Part I

Over the past 20 years, the number and rate of multiple births have dramatically increased in the United States. The rise in multiple births is mainly attributable to the increased use of ovulation-inducing drugs and the newly developed assisted reproductive technologies such as in vitro fertilization. Multifetal gestation is associated with an increased risk of perinatal morbidity and mortality. Multiple births account for an increasing percentage of low-birth-weight infants, preterm births, and infant mortality. In this section, we address the management of the multifetal pregnancy, focusing on the maternal physiology, the diagnosis, the pregnancy outcomes, and the antenatal management of multiple gestation.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to describe the effects of the rising rate of multiple pregnancies on perinatal morbidity and mortality, to recall the complications of diagnosing and treating abnormalities of multiple pregnancies, and to list the many changes that occur in both the mother and the fetuses in multiple pregnancies.

What--and why--the pediatric surgeon should know about twin-to-twin transfusion syndrome

Abstract Endoscopic laser ablation of placental vessels is the most commonly performed fetal operation today. Herein, we review the pathophysiology of twin-to-twin transfusion syndrome and the challenges of its treatment. Pediatric surgeons, with their knowledge of fetal and congenital pathology, and their technical expertise with minimally invasive surgery, can be of great benefit to the patient and the medical team.

A histological study of fetoscopic membrane defects to document membrane healing

OBJECTIVE

To evaluate the rate of spontaneous healing in human fetal membranes after fetoscopy.

STUDY DESIGN

Membranes from patients that had undergone fetoscopic interventions and delivered in one of the two treatment centers were included in the study. The membranes were examined macroscopically for any remaining defects and if present, the size of the defect in chorion and amnion was measured. Subsequently, the defect was excised and stained with HE for histological evaluation. Additional immunohistochemical staining was performed with Ki-67, cytokeratin and vimentin. The proliferation index (percentage of proliferating cells) was calculated in amnion and chorion.

RESULTS

Nineteen membrane defects were included in the study. The median time interval between invasive procedures and delivery was 60 days (range 3-112). All fetoscopic defects (n=19) could be identified in the gestational sac and in none spontaneous closure had occurred. Proliferation indices as measured by inmunohistochemistry were very low (median 2.8%, range 0-7%) in the chorion and 0% in the amnion.

CONCLUSION

No evidence of spontaneous membrane healing was found after fetoscopic procedures, suggesting that the membrane defect normally persists until delivery. Absence of amniotic fluid leakage after invasive procedures may be based on mechanisms other than histologic membrane repair.

Contemporary Treatments for Twin–Twin Transfusion Syndrome

OBJECTIVE

To undertake a systematic review to determine the effects of fetal therapy interventions compared with amniodrainage for twin-twin transfusion syndrome on perinatal survival and outcome.

METHODS

Searching MEDLINE (1966-2004), EMBASE (1988-2004), a hand search of specialist journals, and the Cochrane library (2004:2) identified relevant articles. Studies were selected if the effects of fetal therapeutic interventions for twin-twin transfusion syndrome (laser photocoagulation, serial amnioreduction, septostomy, and selective feticide) on perinatal survival, complications, and morbidity were compared. Study selection, quality assessment, and data abstraction were performed independently and in duplicate.

RESULTS

Only 3 controlled observational studies (comparing treatment in 306 twins) and 1 randomized controlled trial (of 142 twins) were identified. Laser photocoagulation significantly improved perinatal survival of at least 1 fetus and reduced neurologic morbidity compared with serial amnioreduction. No such differences were observed in the comparison of serial amnioreduction with septostomy.

CONCLUSION

In a systematic review of observational and randomized controlled studies, laser photocoagulation of chorionic plate vessels at the intertwin membrane seems to be more effective than serial amnioreduction in the treatment of twin-twin transfusion syndrome with less associated perinatal morbidity and mortality. However, septostomy and selective feticide have not been robustly evaluated.

Biochemical composition of amniotic fluid in pregnancies complicated with twin-twin transfusion syndrome

OBJECTIVE

To compare the electrolyte composition of pregnancies complicated with twin-twin transfusion syndrome (TTTS) with that of physiologic pregnancies.

MATERIALS AND METHODS

Amniotic fluid samples from 16 pregnancies were studied. Specimens were obtained from recipient sacs in 10 pregnancies undergoing fetoscopy for severe midtrimester TTTS. Additionally, 6 amniotic fluid samples were obtained transcervically from legal second-trimester pregnancy terminations. The concentrations of sodium, potassium, chloride, bicarbonate, calcium, glucose, osmolality, pH, total protein content and albumin were determined in each sample.

RESULTS

The mean gestational age at sampling was 20.2 weeks (range 17.2-27.1) in the TTTS group and 18.4 (range 16.0-22.0) in the control group (p = NS). We found significant lower levels of albumin (0.22 +/- 0.04 vs. 0.39 +/- 0.11, p = 0.01) and total protein (0.19 +/- 0.08 vs. 0.51 +/- 0.17, p < 0.001) and higher levels of bicarbonate (16.90 +/- 1.45 vs. 14.50 +/- 2.17, p = 0.02) in amniotic fluid samples taken from recipient sacs of TTTS pregnancies.

CONCLUSION

Amniotic fluid from the receptor in severe midtrimester TTTS differs significantly from control amniotic fluid samples in bicarbonate concentration, total protein content and albumin concentration. These findings may help to understand the pathophysiology of TTTS and to optimise therapeutic modalities.

Persistent elevation of cell-free fetal DNA levels in maternal plasma after selective laser coagulation of chorionic plate anastomoses in severe midgestational twin-twin transfusion syndrome

OBJECTIVE

This study was undertaken to determine whether laser thermocoagulation for twin-twin transfusion syndrome (TTTS) causes increased cell-free fetal DNA levels in maternal plasma, potentially as a result of placental injury.

STUDY DESIGN

We enrolled 34 patients with twin pregnancies complicated by severe TTTS who underwent fetoscopic selective laser ablation of placental vascular anastomoses. Blood samples were drawn before and sequentially after the procedure. Fetal DNA in maternal plasma was quantified by polymerase chain reaction amplification of a Y-chromosome sequence.

RESULTS

Compared with baseline, median elevations of fetal DNA levels were 0.8% at 30 minutes ( P = .32), 15.8% at 60 minutes ( P = .1), 179.5% at 24 hours ( P = .003), and 172.9% at 48 hours ( P = .003). Factors associated with increased fetal DNA levels at 24 hours after procedure included longer operation time, higher number of vessels ablated, and subsequent in utero fetal death ( P = .01, .04, and .04, respectively).

CONCLUSIONS

Persistent elevation of fetal DNA levels in maternal plasma after laser ablation suggests that circulating fetal DNA could derive from placental injury. Plasma fetal DNA analysis may be an additional prognostic marker for fetal outcome after laser therapy.

The long term neurologic outcome of children from pregnancies complicated by twin-to-twin transfusion syndrome

OBJECTIVE

To assess long term outcomes of children from pregnancies complicated by twin-to-twin transfusion syndrome.

DESIGN

Comparison of children from pregnancies with twin-to-twin transfusion syndrome in Western Australia with a contemporaneous regional comparison cohort of preterm and term infants studied using an identical assessment procedure.

POPULATION AND SETTING

All infants aged > or =18 months were identified from a geographically based longitudinal cohort of monochorionic twin pregnancies with an antenatal diagnosis of twin-to-twin transfusion syndrome conducted prospectively since 1992.

METHODS

Children were evaluated using age-specific developmental and behavioural assessments. Cerebral palsy was diagnosed clinically and ascertainment confirmed through the Western Australian Cerebral Palsy Register.

MAIN OUTCOME MEASURES

Intellectual disability, cerebral palsy, behavioural and cognitive function.

RESULTS

Fifty-two children were identified as eligible for study and assessments were performed on 49 (94%). Three surviving children had a diagnosis of cerebral palsy (5.8%). The mean IQ score was 8 points lower in twin-to-twin transfusion syndrome children compared with the comparison cohort although this was mainly due to a decrement of 13 points in those born before 33 weeks of gestation. There was no difference between the donor and the recipient twin in terms of IQ scores (median difference -3, 95% CI -9 to 6). There was no relationship of IQ score to the worst stage of the twin-to-twin transfusion syndrome. Child Behavior Check List and Vineland Adaptive Behavior Scale scores did not differ between twin-to-twin transfusion syndrome children and the comparison group.

CONCLUSIONS

Twin-to-twin transfusion syndrome is associated with a significant reduction in IQ score in very preterm survivors. There seems to be no increase in the prevalence of cerebral palsy. Overall behaviour and adaptive behaviour scale scores are similar to a comparison group.

Characterisation of deep arterio-venous anastomoses within monochorionic placentae by vascular casting

OBJECTIVE

To characterise arterio-venous anastomoses (AVA) in monochorionic (MC) placentae and determine (i) whether shared cotyledons lie beneath the co-termination of an artery from one twin and a vein to the contralateral twin and (ii) whether all AVA can be detected by visual inspection of the chorionic plate.

METHODS

Vascular casts were made of 15 MC placentae. The number of typical AVAs suspected visually before digestion was compared with the number of AVAs identified after acid digestion.

RESULTS

Thirty-three of 67 (49%) suspected typical AVAs were confirmed as typical after casting. There were five false positives and no false negatives. The remainder were classified as atypical AVAs, found in > or =90% of MC placentae. Type I (small vascular connections between two apparently normal cotyledons not seen before casting) and Type II (shared cotyledons arising within larger apparently normal cotyledons) atypical AVAs were found in 53% and 73% of placentae, respectively.

CONCLUSIONS

Only half the shared cotyledons in MC placentae are characterised by co-termination of an artery and vein on the chorionic plate. We report the existence of deep anastomoses beneath the chorionic plate that cannot be visualised by chorionic plate inspection. These findings have implications for laser treatment of twin-twin transfusion syndrome.

Management of fetofetal transfusion syndrome

Feto-fetal transfusion syndrome contributes heavily to high rates of perinatal mortality and morbidity in monochorionic multiple pregnancies. Its prenatal management has been controversial for at least 25 years. We review the recent literature in order to present the basis for a pragmatic reappraisal of the management of this condition. Laser surgery of the chorionic plate inter-twin anastomoses is the best first-line treatment when the syndrome develops before 26 weeks' gestation. Survival (including quality of survival) and gestational age at delivery are improved when compared to serial amnioreduction. Second-line treatment options include repeat-laser, intra-uterine blood transfusion, serial amnioreduction, selective feticide using bipolar cord coagulation or elective delivery, depending upon gestational age and the severity of the disease and its complications. We have found that fetoscopic placental surgery has proven itself over simplicity of amnioreduction. There is no evidence that treatment should be customized according to the stage of the disease at diagnosis. Early recognition of the syndrome through fortnightly serial ultrasound follow-up of all monochorionic pregnancies should ensure timely referral and make up for geographical constraints. Laser surgery should now be available in fetal medicine units that are managing at least 20 cases per year.

Fetofetal transfusion syndrome in triplet pregnancies: outcome after endoscopic laser surgery

OBJECTIVE

The purpose of this study was to determine the outcome of fetofetal transfusion syndrome in triplet pregnancies after treatment with endoscopic laser ablation of communicating placental vessels.

STUDY DESIGN

Cases of severe fetofetal transfusion syndrome that occur in triplet pregnancies and that are treated with endoscopic laser ablation of placental anastomosis were identified from a prospectively collected fetal medicine database. Chorionicity was determined by sonography and classified as dichorionic or monochorionic. Perinatal outcome was obtained in all cases, and long-term follow-up was obtained in all pregnancies that resulted in at least 1 survivor.

RESULTS

During a 6-year period, 10 cases of severe fetofetal transfusion syndrome that were treated with endoscopic laser ablation were identified, of which 7 cases were dichorionic and 3 cases were monochorionic. At least 1 fetus survived in all 7 dichorionic pregnancies and in 2 of the 3 monochorionic pregnancies. In the dichorionic pregnancies, 14 of 21 fetuses (66.7%) survived, but in the monochorionic pregnancies only 2 of 9 fetuses (22.2%) survived.

CONCLUSION

Endoscopic laser ablation is feasible in triplet pregnancies that are complicated by severe fetofetal transfusion syndrome. The treatment appears to be associated with improved perinatal outcome in dichorionic, but not in monochorionic, triplets, probably because of the technical inability in achieving ablation of all the communicating vessels in monochorionic triplets.

Successful patching of iatrogenic rupture of the fetal membranes

Rupture of the fetal membranes is a common, but potentially serious complication of invasive fetal procedures. Quintero described a technique to seal the fetal membrane defect by means of a bloodpatch, usually called 'amniopatch' in this application. The successful use in two consecutive patients with ruptured membranes after a fetoscopic intervention at respectively 17 and 22 weeks' gestational age is described, together with a literature review of published experience.

Ultrasound assessment of venous blood flow before and after laser therapy: approach to understanding the pathophysiology of twin-twin transfusion syndrome

OBJECTIVE

To estimate direction and volume of blood exchange between the donor twin and recipient twin by ultrasound assessment of blood flow in the umbilical vein before and after selective laser photocoagulation of communicating vessels (SLPCV) for twin-twin transfusion syndrome (TTTS).

METHODS

Forty-one TTTS patients underwent Doppler examination of the umbilical vein before and 24 h after SLPCV. The diameter and mean time-averaged velocity of the umbilical vein were estimated. Total umbilical venous flow (TUVF) was calculated as follows: TUVF (mL/min) = mean time-averaged velocity (cm/s) x mean cross-sectional area (cm2) x 60 (s).

RESULTS

TUVF was significantly higher in the recipient (111.2 mL/min) than in the donor twin (44.8 mL/min) before SLPCV (P < 0.0001). However, TUVF was no different between the recipient and the donor twin after SLPCV (93.1 vs. 70.7 mL/min, recipient and donor twin, respectively, P = 0.11). The donor twin's TUVF increased after surgery (P < 0.0001), while the recipient twin's TUVF decreased (P = 0.041). The median postoperative increase in the donor twin's TUVF of 25.9 mL/min had a corresponding decrease of TUVF in the recipient twin of 18.1 mL/min (P = 0.27).

CONCLUSIONS

Our data suggest that untreated TTTS is characterized by excessive umbilical venous blood flow in the recipient twin relative to the donor twin. Laser surgery results in concordant changes in umbilical venous flow in opposite directions between the donor and recipient twins, eliminating the initial imbalance. Our results lend support to the fundamental hypothesis of unbalanced blood flow exchange (net flow from donor to recipient) between monochorionic twins as the cause for TTTS and that laser surgery eliminates the pathophysiological cause.

Endoscopic laser surgery versus serial amnioreduction for severe twin-to-twin transfusion syndrome

BACKGROUND

Monochorionic twin pregnancies complicated by severe twin-to-twin transfusion syndrome at midgestation can be treated by either serial amnioreduction (removal of large volumes of amniotic fluid) or selective fetoscopic laser coagulation of the communicating vessels on the chorionic plate. We conducted a randomized trial to compare the efficacy and safety of these two treatments.

METHODS

Pregnant women with severe twin-to-twin transfusion syndrome before 26 weeks of gestation were randomly assigned to laser therapy or amnioreduction. We assessed perinatal survival of at least one twin (a prespecified primary outcome), survival of at least one twin at six months of age, and survival without neurologic complications at six months of age on the basis of the number of pregnancies or the number of fetuses or infants, as appropriate.

RESULTS

The study was concluded early, after 72 women had been assigned to the laser group and 70 to the amnioreduction group, because a planned interim analysis demonstrated a significant benefit in the laser group. As compared with the amnioreduction group, the laser group had a higher likelihood of the survival of at least one twin to 28 days of age (76 percent vs. 56 percent; relative risk of the death of both fetuses, 0.63; 95 percent confidence interval, 0.25 to 0.93; P=0.009) and 6 months of age (P=0.002). Infants in the laser group also had a lower incidence of cystic periventricular leukomalacia (6 percent vs. 14 percent, P=0.02) and were more likely to be free of neurologic complications at six months of age (52 percent vs. 31 percent, P=0.003).

CONCLUSIONS

Endoscopic laser coagulation of anastomoses is a more effective first-line treatment than serial amnioreduction for severe twin-to-twin transfusion syndrome diagnosed before 26 weeks of gestation.

Management of single fetal demise in a multiple gestation

Intrauterine fetal demise of 1 twin in a multiple gestation is a complex clinical situation. Chorionicity, gestational age at diagnosis, problems specific to the pregnancy, and the emotional needs of the patient can impact management. Strategies to optimize outcomes may include a multidisciplinary team approach and fetal surveillance. The following article reviews (1) adverse fetal and neonatal outcomes associated with intrauterine fetal demise of 1 twin, (2) the potential maternal impact, and (3) the strategies to possibly prevent poor outcomes. It is important to remember that even the most vigilant care may not avoid adverse sequelae in a portion of at-risk pregnancies.

Fetal endoscopic surgery: indications and anaesthetic management

Fetal intervention for certain life-threatening conditions has progressed from being primarily experimental in nature to the standard of care in certain circumstances. While surgical techniques have advanced over the past few years, the anaesthetic goals for these interventions have remained the same; namely, minimizing maternal and fetal risk as well as maximizing the chances of a successful fetal intervention and optimize the conditions necessary to carry the fetus to term gestation. Fetal endoscopic techniques allow access to the fetus without the need for a hysterotomy incision, thus improving the chances of controlled post-operative tocolysis and term gestation after fetal intervention. This procedure, however, is not without associated risks to both fetus and mother. This chapter will address the fetal diseases that may benefit from fetoscopic intervention, the rationale behind why maternal and fetal anaesthesia is required, the various anaesthetics used for these cases and specific considerations of both maternal and fetal physiology that aid in the determination of the best anaesthetic technique for individual cases. Methods of intra-operative fetal monitoring and fetal resuscitation will also be discussed.

Fetal cardiovascular physiology

The cardiovascular system of the fetus is physiologically different than the adult, mature system. Unique characteristics of the myocardium and specific channels of blood flow differentitate the physiology of the fetus from the newborn. Conditions of increased preload and afterload in the fetus, such as sacrococcygeal teratoma and twin-twin transfusion syndrome, result in unique and complex pathophysiological states. Echocardiography has improved our understanding of human fetal cadiovasvular physiology in the normal and diseased states, and has expanded our capability to more effectively treat these disease processes.

Twin-twin transfusion syndrome treated with serial amniocenteses

BACKGROUND

To evaluate the treatment and neonatal outcome in pregnancies complicated by twin-twin transfusion syndrome (TTS).

MATERIAL AND METHODS

Twenty-four women with TTS were identified in the period 1993-99 among 34477 deliveries. We include a retrospective chart review of all twins with TTS.

RESULTS

The overall incidence of TTS was 4.75% of all twin pregnancies. The mean gestational age at the time of diagnosing TTS was 23 weeks (range 17.6-38), and the mean gestational age at delivery was 34.6 weeks (range 23.1-38.3). Therapeutic amniocenteses was performed in 21 women. The total volume drained varied from 0.4 to 32.31 with a mean of 2.3 l. Overall perinatal mortality in TTS was 35.4%, as nine donor twins and eight recipient twins died. The main causes for mortality were intrauterine death and prematurity.

CONCLUSION

Twin-twin transfusion syndrome is a severe complication in monochorionic diamniotic twin pregnancies, with high perinatal mortality and morbidity even though amnioreduction prolonged the pregnancies leading to better neonatal outcome.

Stratégies de diagnostic prénatal et prise en charge des pathologies liées aux grossesses multiples

In the first trimester, ultrasound is crucial to screen for aneuploidies based on nuchal translucency, to diagnose major birth defects, and to establish chorionicity. Indeed prenatal diagnosis strategies as well as obstetrical management options are largely based on placental type. In the second trimester, maternal serum screening is not as effective, and ultrasound screening is more difficult in twins than in singletons. When a severe abnormality in found in one twin, selective termination of pregnancy may be considered. This technique is safe in dichorionic twins, but hazardous in monochorionic pregnancies. Selective termination in dichorionic twins is safer in the first trimester, underscoring the need for early prenatal diagnosis in twins. Monochorionic twin pregnancies carry specific risks, such as the twin-to-twin transfusion syndrome, which can be treated by endoscopic photo-coagulation of intertwin anastomoses in the severe early onset cases, or by amnioreduction in milder cases.

Natural history of twin disruption sequence

Intrauterine death of one fetus in a monochorionic twin pregnancy is associated with high morbidity and mortality in the surviving co-twin. Thromoboplastic material from the dead twin may pass to the circulation of the living twin via placental anastomoses and cause tissue necrosis by direct embolization or by activating intravascular coagulation. Alternatively, acute blood loss into the dying twin through placental anastomoses may result in hypotension and hypoxic-ischemic damage to cerebral and visceral tissue in the surviving twin. The resulting clinical picture is referred to as twin disruption sequence. Affected twins have rarely been followed beyond the neonatal period and the long-term development of such children is unknown. Here, we present a natural history and neurological assessment of 18 patients with twin disruption sequence, whom we have followed over several months to years.

Inducing proliferation of human amnion epithelial and mesenchymal cells for prospective engineering of membrane repair

OBJECTIVE

To prepare a tissue engineering approach to fetal membrane repair after premature rupture of the membranes (PROM) by characterizing the proliferation potential of human amnion epithelial and mesenchymal cells from preterm and term placenta in primary culture.

METHODS

Amnion epithelial and mesenchymal cells from 15 preterm (23-36 week) and 27 term placentas collected at cesarean section were separated enzymatically, characterized immunohistochemically (anti-cytokeratin 18 and anti-E-cadherin, and anti-vimentin, respectively), and their ratio determined. Proliferation on tissue culture polystyrene (TCPS) or collagen in one medium and on TCPS in four different media after 14 days was measured photometrically and compared in preterm vs. term placenta. For statistical analysis the Mann-Whitney test was used.

RESULTS

Preterm and term epithelial:mesenchymal cell ratios were 4.3:1 and 7.8:1. Term epithelial cells proliferated similarly on TCPS or collagen. Mesenchymal cells proliferated only with fetal bovine serum (FBS). Proliferation of term amnion cells in medium containing FBS, epithelial growth factor (EGF), insulin, transferrin and triidothyronine(T3) was significantly increased (p < 0.001) compared with the other three media, and percentage proliferation was slightly higher in preterm cells.

CONCLUSION

Characterization of human amnion epithelial and mesenchymal cells identified the most potent proliferation-inducing medium yet. Studies of the wound-healing potential of these cells are needed, examining their behavior and proliferation on fibrin microbeads and other extracellular matrixes as the next step towards engineering membrane repair in PROM.

Long-term neurodevelopmental outcome in twin-to-twin transfusion syndrome

OBJECTIVE

The purpose of this study was to determine the long-term neurodevelopmental outcome in children after twin-to-twin transfusion syndrome.

STUDY DESIGN

Maternal and neonatal medical records of all twin-to-twin transfusion syndrome patients who were admitted to our center between 1990 and 1998 were reviewed. Neurologic and mental development at school age was assessed during a home visit in all twin-to-twin transfusion syndrome survivors.

RESULTS

A total of 33 pregnancies with twin-to-twin transfusion syndrome were identified. Four couples opted for termination of pregnancy. All other pregnancies were treated conservatively, 18 pregnancies (62%) with serial amnioreductions and 11 pregnancies (38%) without intrauterine interventions. Mean gestational age at delivery was 28.6 weeks (range, 20-37 weeks). The perinatal mortality rate was 50% (29/58 infants). The birth weight of the donor twins was less than the recipient twins (P<.001). Systolic blood pressure at birth was lower in donors than in recipients (P=.023), and donors required inotropic support postnatally more frequently than did recipients (P=.008). The incidence of hypertension at birth was higher in recipients than in donors (P=.038). Abnormal cranial ultrasonographic findings were reported in 41% of the neonates (12/29 neonates). All long-term survivors (n=29 neonates) were assessed during a home visit. Mean gestational age at birth of the surviving twin was 31.6 weeks (range, 25-37 weeks). The mean age at follow-up was 6.2 years (range, 4-11 years). The incidence of cerebral palsy was 21% (6/29 infants). Five of 6 children with cerebral palsy had an abnormal mental development. The incidence of cerebral palsy in the group of survivors who were treated with serial amnioreduction was 26% (5/19 infants). Four children were born after the intrauterine fetal demise of their co-twin, 2 of which had cerebral palsy.

CONCLUSION

The incidence of adverse neurodevelopmental outcome in twin-to-twin transfusion syndrome survivors is high, especially after the intrauterine fetal demise of a co-twin.

Twin-twin transfusion syndrome

The understanding and management of twin-twin transfusion syndrome has evolved significantly over the past few years. Improved and standardized sonographic diagnostic criteria, understanding of the heterogeneic nature of the syndrome, development of an anatomical and reproducible surgical technique for the identification of vascular anastomoses, and technological advances and developments now allow clinicians to view the disease as a more readily understandable and treatable condition. Many tasks remain, including education of peers, better screening and diagnosis, and further development of surgical instruments. Generalization of treatment outcomes should no longer apply given the varied results with disease stage. Confirmation of our tailored approach to management of the disease according to stage should soon be corroborated with an appropriate clinical trial.

The role of Doppler studies in predicting individual intrauterine fetal demise after laser therapy for twin-twin transfusion syndrome

OBJECTIVE

To investigate the role of Doppler studies in predicting individual fetal demise in patients scheduled for selective laser photocoagulation of communicating vessels (SLPCV) for twin-twin transfusion syndrome (TTTS).

METHODS

Doppler studies of the umbilical artery, umbilical vein, ductus venosus, tricuspid valve regurgitation and middle cerebral artery were performed in the donor and recipient twins before and 24 hours after SLPCV. Results were analyzed cross-sectionally and longitudinally. As multiple comparisons were made, an a priori alpha rejection was set at P < 0.001.

RESULTS

One hundred and ten consecutive patients were available for analysis. Overall fetal survival was 68.6% (151/220) with at least one survivor in 88.2% (97/110) of cases. Absent or reversed end-diastolic velocity in the umbilical artery of the donor twin was the only preoperative Doppler result predictive of intrauterine fetal demise (IUFD) (10/15, 66.7%, P < 0.001). Postoperatively, reversed flow during atrial contraction in the ductus venosus of the donor twin showed a trend towards prediction of IUFD of this fetus (4/5, 80%, P = 0.007). No other Doppler studies, including the longitudinal analyses, were predictive of IUFD.

CONCLUSIONS

Our data suggest that preoperative absent or reversed end-diastolic velocity in the umbilical artery may be useful in predicting individual fetal demise of the donor twin in TTTS patients scheduled for SLPCV. This may reflect the role of decreased individual placental mass that may be associated with some donor twins. The inability of other Doppler studies to predict individual IUFD may be explained preoperatively by the effect of the interfetal vascular connections on the individual Doppler signals and postoperatively by the effect of surgery or the timing of the assessment. Our findings may be important in patient counseling, in furthering understanding of the disease, and perhaps in improving surgical technique.

Transient hydrops fetalis of the donor fetus in twin-twin transfusion syndrome after therapeutic amnioreduction

We present a case of twin-twin transfusion syndrome associated with transient hydrops fetalis observed in the donor after therapeutic amnioreduction at 22 weeks of gestation. After the amnioreduction, the bladder of the donor could be visualized and the donor subsequently began to make amniotic fluid, with spontaneous regression of hydrops fetalis. It is suspected that after therapeutic amnioreduction, intrauterine hemodynamic changes occurred and the donor developed transient hydrops fetalis due to volume overload.

Fetal hypertension: an insight into the pathogenesis of the twin-twin transfusion syndrome

OBJECTIVES

To investigate if systemic hypertension occurs in fetuses with twin-to-twin transfusion syndrome (TTTS).

METHODS

We conducted an observational cohort study in a tertiary care centre in 23 pregnant women with TTTS. Polyhydramnios stuck twin sequence occurred at a median gestational age of 22 weeks (range 15-27). Biventricular myocardial hypertrophy was diagnosed in 22/23 recipient fetuses. In cases with atrioventricular valve regurgitation (AVR), it was possible to estimate the fetal systolic systemic blood pressure by ultrasound, on the basis of the simplified Bernouilli equation. The diagnosis of fetal hypertension (FHT) was made when the estimated systolic arterial pressure was equal to or above 1.6-fold the expected value.

RESULTS

In 10 pregnancies (group A), fetal blood pressure could be assessed in recipients with AVR. The maximum velocities ranged from 2.9 to 5 m/s, leading to estimates of systemic fetal arterial pressure from 37 to 104 mmHg, that is, 1.6- to 2.8-fold the expected values. In 13 pregnancies (group B), fetal blood pressure could not be assessed in the absence of AVR. In group A, perinatal death (16/20) and hydrops (7/20) were significantly more frequent than in group B (8/26 and 1/26 respectively).

CONCLUSION

Fetal systemic hypertension may occur in recipient twins and could play a role in the pathophysiology of TTTS.

Complications of monochorionic twins

Sonography has made a dramatic impact on the obstetric management of complicated twin pregnancies. This is based in part on the ability to use prenatal US to diagnose syndromes and complications of MC twinning. All twin pregnancies are at high risk for perinatal morbidity and mortality compared with singleton gestations, but when one of the described complications is recognized, the difficulties in management are compounded dramatically. Despite the relative rarity of some of the entities described, it is vitally important to be familiar with these problems and their sonographic evaluation and diagnosis.

Minimal access fetal surgery

The development of fetal surgery has led to promising therapeutic options for a number of congenital malformations. However, preterm labor (PTL) and premature rupture of membranes continue to be ubiquitous risks for both mother and fetus. To reduce maternal morbidity and the risk of prematurity, minimal access surgical techniques were developed and are increasingly employed. Congenital diaphragmatic hernia (CDH), obstructive uropathy, twin-to-twin transfusion syndrome (TTTS), and sacrococcygeal teratoma have already been successfully treated using minimal access fetal surgical procedures. Other life-threatening diseases as well as severely disabling but not life-threatening conditions are potentially amenable to treatment. The wider application of minimal access fetal surgery depends on a continued improvement in technology and a better understanding of complications associated with fetal intervention.

Stage-based treatment of twin-twin transfusion syndrome

OBJECTIVE

The purpose of this study was to compare the outcomes of patients with twin-twin transfusion syndrome who were treated with either serial amniocentesis or selective laser photocoagulation of communicating vessels according to disease severity (stage).

STUDY DESIGN

Centers that were experienced in the treatment of twin-twin transfusion syndrome were invited to share stage-based perinatal outcome data. All patients met basic standard sonographic criteria for twin-twin transfusion syndrome (polyhydramnios maximum vertical pocket, > or =8 cm; oligohydramnios maximum vertical pocket, < or =2 cm). Gestational age at first treatment was <27 weeks of gestation.

RESULTS

Three centers submitted stage-based data, for a total of 173 patients (serial amniocentesis, 78 patients from all 3 centers) and 95 selective laser photocoagulation of communicating vessels (1 center). The distribution of patients by stage was similar in the two groups. Successful pregnancy outcome (at least 1 surviving infant) was correlated inversely with stage in the serial amniocentesis but not in the selective laser photocoagulation of communicating vessels group and was significantly lower in the serial amniocentesis (66.7%) than in the selective laser photocoagulation of communicating vessels group (83.2%). Neurologic morbidity was related directly to stage in the serial amniocentesis group but not in the selective laser photocoagulation of communicating vessels group and was significantly higher in the serial amniocentesis (24.4%) than in the selective laser photocoagulation of communicating vessels (4.2%) group. Intact neurologic survival (at least 1 surviving infant without neurologic morbidity) was significantly lower in the serial amniocentesis group than in the selective laser photocoagulation of communicating vessel group (51.3% vs 78.9%), particularly in stage III and stage IV (23.5% vs 72.7% in stage IV). Patients who were treated with selective laser photocoagulation of communicating vessels were 2.4 times more likely to have at least one survivor than those treated with serial amniocentesis.

CONCLUSION

Our study suggests a relationship between perinatal morbidity and mortality rates and stage in serial amniocentesis but not in selective laser photocoagulation of communicating vessel-treated twin-twin transfusion syndrome patients. These findings could be used to tailor the treatment of twin-twin transfusion syndrome. A clinical trial to confirm these results is being organized by our research groups.

Monochorionic diamniotic twins: complications and management options

PURPOSE OF REVIEW

Monochorionic compared with dichorionic twins have disproportionately high fetal loss rates, perinatal mortality and morbidity. This is because of the unpredictable vascular anastomoses and the often asymmetrical distribution of the single placenta between both twins.

RECENT FINDINGS

The pathophysiology of twin-to-twin transfusion syndrome is usually explained on an angioarchitectural basis, although certain hemodynamic and hormonal factors also may be involved. The results of the large randomized trials on amnioreduction, fetoscopic laser coagulation and septostomy are still awaited. An update is given on hardware and instruments required for fetoscopic laser. Subsequently, the problem of the monochorionic twin set with severe early discordant growth is addressed. Several etiological mechanisms have been proposed, but little is known of its natural history. Also, umbilical artery Doppler waveforms may not have the same predictive value as in singletons. Prophylactic laser coagulation of the vascular anastomoses to protect against the adverse effects of single intrauterine demise, has so far not been shown to confer any benefit in outcome. Finally, pathophysiology and management of discordant structural and chromosomal anomalies in monochorionic twins are discussed. Laser and monopolar coagulation, which can be introduced through a needle, may be used for selective feticide in early pregnancy or low hemodynamic conditions. Bipolar coagulation seems more effective at later gestational ages and normal hemodynamic conditions.

SUMMARY

Our insight into the complications associated with monochorionic twins has increased in recent years. It is hoped that this will lead to better surveillance and ultimately an improved outcome for these high-risk pregnancies.

Fetal endoscopic surgery: lessons learned and trends reviewed

PURPOSE

Fetal surgery is performed increasingly with minimal access approaches. The authors report their experience with fetal endoscopic procedures (fetendo) with emphasis on changing techniques and outcome trends.

METHODS

All fetal endoscopic cases performed at a single institution from January 1996 to August 2001 were reviewed (n = 66). Cases were examined with respect to year performed, type of operation, operative data, and outcome.

RESULTS

Twin-twin transfusion syndrome (26 cases) and congenital diaphragmatic hernia (35 cases) were the most common diseases treated. From 1996 to 2001, there was a decrease in average operating time (256 to 127 minutes [P =.0006]), number of ports utilized (3.8 to one [P =.00001]), pump volume (28.7 to 2.7 L [P =.00001]), and estimated blood loss (408 to 29 mL [P =.008]). In addition, port size changed from 10 mm to 5 mm. Chorioamniotic separation (31 of 66), premature rupture of membranes (32 of 66), chorioamnionitis (12 of 66), and fetal death (10 of 66) continued to be significant complications.

CONCLUSIONS

Fetal endoscopic surgery over the last 6 years has evolved toward shorter operating time, the use of smaller and fewer ports, decreased pump fluid exchange, and decreased blood loss, with the types of cases centered on twin-twin transfusion syndrome and congenital diaphragmatic hernia.

Understanding twin-twin transfusion syndrome: role of Doppler ultrasound

The high risks of monochorionic (MC) twin gestations are largely related to the vascular anatomy of the shared placentae and the presence of intertwin vascular connections. These anastomoses are implicated in twin-twin transfusion syndrome and co-twin sequelae after intrauterine death of one twin. Twin-twin transfusion syndrome is the most common complication of MC twinning. Obstetrical sonography, with the use of Doppler techniques, can be used to assess these high-risk pregnancies and to interrogate the vascular connections in the shared placentae. The information obtained can improve our understanding of the pathophysiology of syndromes that complicate these pregnancies and may help inform obstetrical management.

Monoamniotic twins: diagnosis and management

Monoamniotic twins, although uncommon, are associated with high antenatal and perinatal morbidity and mortality. The associated complications include cord entanglement, congenital anomalies, twin-twin transfusion syndrome, intrauterine growth retardation and preterm delivery. A thorough literature search using Medline and OVID was performed to look at the current diagnostic criteria for monoamniotic twins and the subsequent management. Specific criteria are employed during ultrasonography for making the diagnosis. Different opinions in the literature exist regarding the proper antepartum monitoring of monoamniotic twins, the optimal timing and the mode of delivery. Generally, it is agreed that there should be regular antepartum fetal heart trace monitoring and serial sonograms with umbilical artery Doppler flow study. Most studies advocate delivery at 32 weeks to reduce the risk of intrauterine deaths related to cord entanglement. Cesarean section is the preferred mode of delivery even though cases of successful vaginal delivery have been reported.

Management of single fetal death in twin-to-twin transfusion syndrome: a role for fetal blood sampling

OBJECTIVE

Intrauterine death of one twin in monochorionic pregnancies is associated with an increased mortality and morbidity of the cotwin. This is likely to occur as a consequence of acute hemodynamic changes due to feto-fetal hemorrhage at the time of death of the cotwin. We assessed the role of fetal blood sampling and intrauterine transfusion to rescue the survivor.

MATERIALS AND METHODS

We managed 12 cases of single intrauterine death at between 17 and 26 weeks' gestation in monochorionic twins complicated by twin-to-twin transfusion syndrome (TTTS). All these cases had been treated either by laser therapy or by serial amniodrainage. When the demise of one twin occurred, ultrasound-guided fetal blood sampling was performed in the surviving twin using a 20-gauge needle within 24 h of death. Intrauterine transfusion was performed at the same time in cases where the survivor was anemic. All survivors were assessed in the neonatal period and at 1 year of age.

RESULTS

Six of the 12 surviving fetuses were found to be anemic and underwent intrauterine transfusion. All fetuses survived the procedure. Four of these fetuses had normal neurological development at 1 year of age. Periventricular leukomalacia developed in one case and the patient underwent termination of pregnancy at 34 weeks. In one case delivery occurred at 34 weeks' gestation and the baby developed periventricular leukomalacia at 1 month of age. In all six non-anemic fetuses pediatric examination was normal at birth and at 1 year of age.

CONCLUSION

Intrauterine death of one monochorionic twin in TTTS puts the survivor at high risk of intrauterine death or of developing ischemic/hypoxic lesions. Our results suggest that fetal blood sampling is a useful diagnostic tool to identify those fetuses that are not anemic and hence unlikely to be at risk of developing a cerebral lesion.

Impact of laser coagulation in severe twin-twin transfusion syndrome on fetal Doppler indices and venous blood flow volume

OBJECTIVE

To evaluate the impact of fetoscopic laser coagulation of placental anastomoses in severe twin-twin transfusion syndrome on fetal Doppler indices and umbilical vein blood flow volume as calculated with Doppler and two-dimensional ultrasound.

METHODS

Thirty-two cases of second-trimester severe twin-twin transfusion undergoing laser therapy were examined with serial ultrasound before and 1, 3 and 5 days after therapy. Pulsatility indices in the umbilical artery and ductus venosus were measured. Blood volume flow at the level of the intra-abdominal umbilical vein was calculated by means of Doppler and two-dimensional ultrasound. The development of hydropic signs in donors was recorded. Perinatal outcome in terms of neonatal survival was recorded for all cases.

RESULTS

In recipients, ductus venosus pulsatility index decreased progressively after therapy and, by day 5, median pulsatility index was significantly lower than that before therapy (0.97 vs. 0.82, P < 0.0001). Umbilical vein blood flow volume in recipient twins showed no significant variations before and after laser. In donors, umbilical artery pulsatility index decreased significantly by the first day following therapy (2.1 vs. 1.6, P < 0.0001). Previously absent or reverse umbilical end-diastolic flow reappeared after therapy in 46% (7/15) of donors. Ductus venosus pulsatility index in donors increased significantly by day 1 after therapy (0.99 vs. 1.35, P < 0.0001) but, over days 3 and 5, it returned towards preoperative values. Umbilical vein flow volume measurements (mL/min/kg) in the donor increased by approximately 50% the day after treatment (151 vs. 232, P < 0.0001) and remained elevated. Umbilical vein flow volume before laser therapy was significantly lower in donors compared to recipients (151 vs. 260, P < 0.0001), but the difference was non-significant after treatment (240 vs. 267). One or more hydropic signs developed in eight (25%) donors during the 5 days' observation after therapy.

CONCLUSIONS

Laser therapy induced important changes in fetal hemodynamic parameters, resulting in a reversion of the disturbances associated with severe twin-twin transfusion syndrome. The recipient twin showed a progressive improvement of previous signs of right cardiac overload. The donor experienced a substantial increase in umbilical vein blood volume flow accompanied by a transitory state of relative right overload, which may explain the development of transient hydropic signs in a proportion of donors.

The twin-twin transfusion syndrome

The aetiology of twin-twin transfusion syndrome (TTTS), which affects 10-15% of monochorionic (MC) twin pregnancies, remains poorly understood. Although all MC twins have placental vascular anastomoses, unbalanced intertwin transfusion has been shown by ex vivo injection and in vivo Doppler studies of chorionic plate vasculature to be mediated by > or =1 arterio-venous anastomoses (AVA) in association with absent bi-directional arterio-arterial anastomoses (AAA). TTTS presents in the mid trimester with the oligo-polyhydramnios sequence, the donor may have a small or non-visible bladder and abnormal umbilical artery Doppler, while the recipient has a large bladder and may develop cardiac hypertrophy, triscupid regurgitation, and eventually hydrops. Recently, discordant renal renin angiotensin expression, endothelin and atrial natriuretic peptide have been implicated in the pathogenesis. Survival has increased from <20% to <60-70% with modern treatments, although survivors remain at increased risk of antenatally acquired cerebral white matter injury, and neurodevelopmental sequelae are documented in c.10% (range 5-23%). The recent introduction of a staging system for TTTS facilitates selection of therapy with less invasive amnioreduction and septostomy preferred for early stage disease, and more aggressive modalities such as laser ablation and cord occlusion with their attendant risk of procedure related fetal loss, reserved for advanced stage disease.

Transient hydropic signs in the donor fetus after fetoscopic laser coagulation in severe twin-twin transfusion syndrome: incidence and clinical relevance

OBJECTIVE

To evaluate the incidence, characteristics, and impact on perinatal outcome of the development of hydropic signs in the donor fetus after laser coagulation for severe twin-twin transfusion syndrome in the second trimester.

METHODS

Forty cases of second-trimester severe twin-twin transfusion underwent fetoscopic laser coagulation of placental anastomoses and were followed up with serial ultrasound up to 14 days after therapy. Ultrasound scans were performed just before, and on days 1, 3, 5 and 14 after therapy, and fetuses were monitored for the presence of hydropic signs (skin edema, pleural effusion, ascites and pericardial effusion). Response to therapy and perinatal outcome in terms of neonatal survival were recorded for all cases.

RESULTS

Four recipients (10%) and three donors (7.5%) died over the first 72 h after therapy. During the study period, two recipients (5.5%) developed frank hydrops fetalis, and eventually died in utero. Ten donors (27.0%) developed one or more hydropic signs. In nine (90%), signs were mild or moderate and transient (mean, 3.2 days), while in one case hydrops worsened and the fetus eventually died. No donors with transient hydrops died in utero, and two died postnatally due to extreme prematurity. Gestational age at procedure and deepest amniotic fluid vertical pocket were similar between hydropic and non-hydropic donors. Discrepancy in estimated fetal weight at procedure was significantly lower in donors developing hydrops (9.6 (SD, 6.4) vs. 17.8 (14.4)%,P = 0.018). In pregnancies with hydropic donors, gestational age at delivery (33.1 (3.4) vs. 29.7 (3.5) weeks,P = 0.015) and birth weight for recipient (2392 (423) vs. 1631 (576) g, P < 0.001) and donor (1908 (774) vs. 1281 (583) g,P = 0.021) were significantly higher. The development of transient hydrops had no influence on neonatal survival at 28 days nor on the rate of clinical resolution of intertwin transfusion.

CONCLUSIONS

Transient hydropic signs may develop in a proportion of donor fetuses after laser coagulation for severe twin-twin transfusion syndrome. This phenomenon is normally not associated with a poor prognosis, and possibly indicates an hemodynamic adaptation response following interruption of the transfusion process.

Prenatal diagnosis for multiple pregnancies

In multiple pregnancies, first trimester ultrasound is crucial to diagnose chorionicity, to detect major structural defects, and to screen for chromosomal abnormalities based on nuchal translucency measurement. The efficacy of nuchal translucency measurement screening in twins might be improved when combined with first trimester maternal serum screening. In twins as in singletons, the risk of fetal loss attendant to chorionic villi sampling and to amniocentesis are similar. When an invasive procedure is indicated in twins, chorionic villi sampling has, over amniocentesis, the advantage of allowing selective termination to be performed in the first trimester, when the procedure related risk of miscarriage is minimal. It has the disadvantage of leading to ambiguous results in up to 2% of cases. While chorionic villi sampling is the choice technique in pregnancies at very high risk, amniocentesis is still indicated in cases at more moderate risk. In monochorionic pregnancies, selective termination can now be performed using a variety of techniques including bipolar or monopolar cord coagulation, and, in acardiac twins, alcohol ablation. However, selective termination remains more hazardous in monochorionic than in dichorionic pregnancies. The outcome of the twin-to-twin transfusion syndrome has been substantially improved by laser photocoagulation of placental shunts and by amniodrainage, but randomized trials are needed to establish the optimal therapeutic strategy, and further pathophysiologic research might result in new treatments.