Twin-twin transfusion syndrome: the 'Select' procedure

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

Approximately 20% of all twin pregnancies are monochorionic. Between 9% and 15% of all monochorionic twin gestations are complicated by severe chronic twin-to-twin transfusion syndrome (TTTS), characterized by a gradual shift of blood volume from the donor twin to the recipient twin through placental vascular connections [1 - 3] . The prognosis of severe, untreated chronic TTTS diagnosed in midtrimester fetuses is extremely poor, with mortality rates exceeding 70% [4] . Since publication of the results of the Eurofoetus trial in 2004, laser photocoagulation of the intertwin anastomoses has become accepted as the optimal first-line therapy for severe TTTS diagnosed before 26 weeks of gestation. While laser treatment of vascular communications was initially limited to selected fetal treatment centers, its increasingly widespread use has resulted in the exposure of more pathologists, even in less specialized institutions, to laser-treated placentas. Furthermore, the surge in laser coagulation has revived the general medical, scientific, and public interest in the placental and choriovascular findings in monochorionic twin placentas. The pathologist's understanding of the pathophysiology of TTTS and of TTTS-associated placental pathology, including the findings related to laser ablation of the anastomoses, can be of great benefit to the involved obstetric/neonatal/surgical team and, ultimately, to the patients. In this review, we summarize the current knowledge of the placental contributions to TTTS and other complications of monochorionic twinning and describe the strengths and limitations of placental examination in these settings. It is our expectation that overviews such as this may serve as a template to generate consensus guidelines for standardized and evidence-based pathologic evaluation of monochorionic twin placentas.

Placentation in Multiple Births

Outcomes of multifetal pregnancy in prenatal life are markedly affected by chorionicity. Several disease processes are found in monochorionic (MC) twins that do not occur in dichorionic (DC) twins. Improvements in prenatal outcomes will depend on reliable first trimester diagnosis of chorionicity, allowing early monitoring for complications of MC placentation. Particular structures and functions of MC twin placentas affect outcomes and can be targeted for specific treatments, especially in twin-twin transfusion. The causes of severe DC twin fetal growth discordance are clarified. In post-natal life, zygosity is a determining effect in genetic predisposition to many chronic diseases, including neoplasia. Few MC twins know that they are monozygotic (MZ). Few twin researchers realize that MZ twins may be genetically discordant. Abandonment of the word “identical” for MZ twins would assist in clarifying these issues of zygosity, concordance and discordance.

Maternal complications of fetoscopic laser photocoagulation (FLP) for treatment of twin-twin transfusion syndrome (TTTS)

AIMS

Fetoscopic laser photocoagulation (FLP) has become standard therapy for severe twin-twin transfusion syndrome. Data on adverse maternal events are rare. We performed a literature review to obtain data on maternal complications of FLP.

METHODS

Extensive literature review, searching MEDLINE and other databases from 1990 to 2009, using MESH-terms and further keywords. Data extraction was performed using the following criteria: (i) maternal complications reported as primary or secondary outcome parameters; (ii) any comment on adverse maternal events.

RESULTS

Of 321 publications found 40 were included, comprising 1785 patients. The overall rate of adverse maternal events was 5.4%. In studies with systematic assessment (n=3, 379 patients) the complication rate was significantly higher (17.4% vs. 2.2%, P<0.0001). Adverse events were classified and the rate was 1.0% (1.8% vs. 0.8%, P=0.12) for severe complications; 2.9% (11.9% vs. 0.5%, P<0.0001) for intermediate/minor adverse events; and 1.5% (3.7% vs. 0.9%, P<0.0001) for complications with undetermined relevance.

CONCLUSIONS

High-quality data on maternal complications of FLP are rare. With systematic assessment, the rate of adverse events is significantly higher. Underreporting has to be assumed. Further studies are required to confirm these data.

A prospective study of albuminuria and cognitive function in older adults: the Rancho Bernardo study

Chronic kidney disease is a risk factor for cognitive impairment. Albuminuria is an early manifestation of chronic kidney disease and a marker of endothelial dysfunction and vascular risk. Results of prior studies of albuminuria and cognitive function are contradictory. The authors studied 1,345 community-dwelling women and men in southern California (mean age, 75 years) at a 1992-1996 research clinic visit, when urine albumin/creatinine ratio (ACR) was measured in spot morning urine and cognitive function was evaluated by using the Mini-Mental State Examination Trail-Making Test B, and category fluency test. An ACR of > or =30 mg/g was found in 17% of women and 15% of men in 1992-1996. Analysis of covariance was used to compare cognitive function score by categorical ACR. Between 1999 and 2002, 759 participants returned for repeat cognitive function testing. For men, but not women, baseline albuminuria, but not estimated glomerular filtration rate, was associated with reduced cognitive function at follow-up on all tests (P's < 0.05). An ACR of > or =30 mg/g was associated with greater annual decline in Mini-Mental State Examination and category fluency scores. Albuminuria may be an easily measured marker predicting future cognitive function decline. Results imply a common underlying mechanism affecting the renal and cerebral microvasculature.

Antenatal detection of arteriovenous anastomoses in monochorionic twin pregnancy

OBJECTIVES

To revalidate the detection technique for arteriovenous anastomoses in an unselected group of monochorionic twins, and to make recommendations about its applicability for more widespread use.

METHODS

Women with monochorionic diamniotic (MCDA) twins were recruited and underwent placental mapping by color Doppler ultrasound. Images of placental maps showing the location and type of anastomoses were saved as digital video clips. After delivery, dye injection study of all the placentas was performed to delineate the site and type of anastomoses. A digital photograph of each injection study was taken and saved. The antenatal ultrasound images and postnatal dye injection studies were compared.

RESULTS

18 sets MCDA twins were evaluated. In 3 cases there was evidence of twin-to-twin transfusion syndrome. Dye injection of 18 placentas revealed 21 arterio-arterial anastomoses (AAA), 21 arteriovenous anastomoses (AVA) and 4 veno-venous anastomoses (VVA). Of these, 10 (48%) AAAs and 5 (24%) AVAs were detected antenatally by color Doppler. In all cases, where an AVA was detected, the placenta was located anteriorly.

CONCLUSION

Antenatal detection of AVA was feasible when the placenta was located anteriorly, but proved difficult in posteriorly situated placentas.

Miniature bending manipulator for fetoscopic intrauterine laser therapy to treat twin-to-twin transfusion syndrome

BACKGROUND

Recent typical therapy for twin-to-twin transfusion syndrome (TTTS) is selective laser photocoagulation of anastomotic communicating vessels on the placenta using the fetoscopic approach. The difficulty of a conventional laser device approach for this procedure depends significantly on the placental location, so a new robotized device is required to bend the direction of laser irradiation flexibly within the narrow uterus.

METHODS

The authors designed a miniature bending mechanism impelled by a wire-guided linkage driving method that provides a stable procedure for bending laser irradiation from -90 degrees to 90 degrees . Using this bending mechanism, the authors developed a bending manipulator with a diameter of 3.5 mm and a hollow central channel with a diameter of 0.8 mm for passing a glass fiber for neodymium:yttrium-aluminum-garnet (Nd:YAG) laser photocoagulation. The bending mechanism is motorized by an electrical actuator and controlled by a grip-type interface with a small joystick. The robotized tip's part and the actuator's part are easily separable for cleaning and sterilization.

RESULTS

In performance evaluations of the manipulator, the bending characteristics with a glass fiber were examined. The bending range was -52.6 degrees to 80 degrees, with a very small hysteresis error, and the bending repeatability error was 0.5 degrees +/- 0.2 degrees, which corresponds with the high accuracy of 0.2 +/- 0.1-mm positioning error at the glass fiber's tip. In the evaluation of Nd:YAG laser photocoagulation, the study confirmed that the manipulator performed effective laser photocoagulation of the placental phantom surface (underwater chicken liver). The large bending range, reaching 80 degrees, enabled a flexible approach from various directions with a high irradiation efficiency of no less than 96.6%.

CONCLUSIONS

The authors' original miniature bending manipulator can change the laser irradiating direction with highly repeatable positioning accuracy for speedy, safe, and effective vessel occlusion in clinical practice.

Maternal morbidity after maternal-fetal surgery

OBJECTIVE

There is a paucity of published data on the maternal risks of fetal surgical interventions. We analyzed maternal morbidity and mortality that were associated with different types of fetal intervention (open hysterotomy, various endoscopic procedures and percutaneous techniques) to quantify this risk.

STUDY DESIGN

We performed a retrospective evaluation of a continuous series of 187 cases that had been performed between July 1989 and May 2003 at the Fetal Treatment Center, a highly specialized interdisciplinary center for fetal surgery at the University of California, San Francisco. The primary outcome was the frequency of maternal morbidity for open, endoscopic, and percutaneous procedures to access the fetus.

RESULTS

There were 187 pregnant women with confirmed major fetal malformations who were candidates for intrauterine fetal intervention. Maternal-fetal surgery was performed in 87 cases by open hysterotomy, in 69 cases by endoscopic procedures, and in 31 cases by percutaneous techniques. There were no maternal deaths, but significant short-term morbidity was observed. There were no significant differences in the incidence of premature rupture of membranes, pulmonary edema, placental abruption, postoperative vaginal bleeding, preterm delivery, or interval from maternal-fetal surgery to delivery between endoscopic procedures and open surgery. Complications were significantly less in the percutaneous ultrasound-guided procedures. Endoscopic procedures, even with a laparotomy, showed statistically significantly less morbidity compared with the open hysterotomy group regarding cesarean delivery as delivery mode (94.8% vs 58.8%; P < .001), requirement for intensive care unit stay (1.4% vs 26.4%; P < .001), length of hospital stay (7.9 vs 11.9 days; P = .001), and requirement for blood transfusions (2.9% vs 12.6%; P = .022). Chorion-amnion membrane separation (64.7% vs 20.3%; P < .001) was seen more often in the endoscopy group.

CONCLUSION

Short-term morbidities include increased rates of cesarean birth, treatment in intensive care, prolonged hospitalization, and blood transfusion, all of which were more common with hysterotomy compared with other techniques. Maternal-fetal surgery can be performed without maternal death. Results from this study provide helpful data for counseling prospective patients.

Invasive Antenatal Interventions in Complicated Multiple Pregnancies

Multiple pregnancies still pose challenging problems for modern medicine. Complications in monochorionic multiple pregnancies have sparked a revival of fetoscopy as a means surgery on the placenta and umbilical cord. As such, fetoscopic laser coagulation is currently the best first-line treatment for severe twin-to-twin transfusion syndrome. Also, fetoscopic or ultrasound-guided cord coagulation seems to be an effective technique for selective feticide in monochorionic twins, albeit with still considerably higher fetal loss rates compared with selective feticide by potassium chloride injection in dichorionic twins.

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.

Fetal therapy

The advances in fetal therapy including endoscopic approaches and the advent of safer anesthetic techniques has led to the intrauterine management of potentially lethal diseases or diseases associated with high morbidity. This review will elicit certain newer techniques for fetal therapy including their application and complications.

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.

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.

Fetal and neonatal outcomes in twin oligohydramnios-polyhydramnios sequence including cerebral palsy

OBJECTIVE

The purpose of this study was to review consecutive pregnancies complicated by twin oligohydramnios-polyhydramnios sequence (TOPS) and to clarify the probable factors influencing the perinatal outcomes.

METHODS

Twenty-five pregnancies with a diagnosis of TOPS were treated with and without amniocentesis. A poor perinatal outcome was defined when either perinatal mortality or cerebral palsy was observed.

RESULTS

The mean gestational age at the time of diagnosis and of delivery was 27.8 (range 21-34) and 30.7 (range 23-35) weeks, respectively. Tocolytic therapy and therapeutic amniocentesis were done in 16 (64%) and 13 (52%) cases. Hydrops fetalis was present in 10 cases. The survival rate was 72%, and cerebral palsy was diagnosed in 8 of 36 infants (22%). The poor prognostic factors were gestational age at delivery (<30 weeks) and presence of symptomatic preterm labor and hydrops fetalis. Therapeutic amniocentesis did not influence the perinatal outcome.

CONCLUSIONS

In this observational study, the long-term as well as the short-term perinatal outcome of pregnancy with TOPS seems to be poor. In addition, therapeutic amniocentesis in TOPS does not appear to affect fetal and neonatal outcomes.

Evaluation of practice effects in language and spatial processing test performance

Recent research demonstrates that practice effects are attenuated through the administration of alternate-form memory tests. However, little is known about the degree of practice that can be expected when alternate forms of nonmemory tests are administered repeatedly. Two groups of healthy older adults were assigned to either a same- or alternate-forms condition. Participants completing the same forms of a confrontation naming task improved significantly over 4 testing sessions. On verbal fluency, participant performance significantly improved when completing only alternate forms. No significant practice effects were observed on tests of spatial processing. Practice effects caused by item-specific practice may be reduced via alternate test forms. However, similar reductions will be less apparent when practice effects are the result of test-specific practice.

Longitudinal analysis of the effects of the aging process on neuropsychological test performance in the healthy young-old and oldest-old

A sample of 33 young-old (ages 65 to 74) and 20 oldest-old (ages 84 to 93) healthy elderly without dementia were assessed with neuropsychological tests annually over a 4-year period to examine longitudinal changes in cognitive functioning. Significant age-group differences existed at baseline in participants' performances on tests of immediate memory and visuospatial skills. There were no age-group differences in the rate of change over the 4-year interval on any neuropsychological tests. Within each age-group, the amount of change over time was minimal for most tests though some practice effects were apparent, and on some tests mild decline was observed. Results suggest that healthy old adults, including the oldest-old, do not experience measurable declines in cognitive functioning over a 4-year period.

Doppler sonographic demonstration of arterio-venous anastomosis in monochorionic twin gestation

Arterio-venous connections, which are known to occur in monochorionic twin placentae and are a mechanism for the development of twin-to-twin transfusion syndrome, can be demonstrated in utero by means of targeted sonography with the use of spectral and color flow Doppler techniques.