Residual Anastomoses After Fetoscopic Laser Surgery in Twin-to-Twin Transfusion Syndrome: Frequency, Associated Risks and Outcome

Placental architectural characteristics following laser ablation within monochorionic twins complicated by twin-twin transfusion syndrome: A systematic review and meta-analysis of outcomes

INTRODUCTION

Twin-twin transfusion syndrome (TTTS) complicates approximately 10%-15% of all monochorionic twin pregnancies. The aim of this review was to evaluate the placental architectural characteristics within TTTS twins following laser and elucidate their impact on fetal outcomes and operative success.

MATERIAL AND METHODS

Five databases were searched from inception to August 2023. Studies detailing post-delivery placental analysis within TTTS twins post-laser were included. Studies were categorized into two main groups: (1) residual anastomoses following laser and (2) abnormal cord insertion: either velamentous and/or marginal or proximate. The primary outcome was to determine the proportion of TTTS placentas with residual anastomoses and abnormal cord insertions post-laser. Secondary outcomes included assessing residual anastomoses on post-laser fetal outcomes and assessing the relationship between abnormal cord insertion and TTTS development. Study bias was critiqued using the Joanna Briggs Institute checklists and Cochrane risk of bias tool. Random-effects meta-analysis was used, and results were reported as pooled proportions or odds ratio (OR) with 95% confidence interval (CI). PROSPERO registration: CRD42023476875.

RESULTS

Twenty-six studies, comprising 4013 monochorionic twins, were included for analysis. The proportion of TTTS placentas with residual anastomoses following laser was 24% (95% CI, 0.12-0.41), with a mean and standard deviation of 4.03 ± 2.95 anastomoses per placenta. Post-laser residual anastomoses were significantly associated with intrauterine fetal death (OR, 2.38 [95% CI, 1.33-4.26]), neonatal death (OR, 3.37 [95% CI, 1.65-6.88]), recurrent TTTS (OR, 24.33 [95% CI, 6.64-89.12]), and twin anemia polycythemia sequence (OR, 13.54 [95% CI, 6.36-28.85]). Combined abnormal cord (velamentous and marginal), velamentous cord, and marginal cord insertions within one or both twins following laser were reported at rates of 49% (95% CI, 0.39-0.59), 27% (95% CI, 0.18-0.38), and 28% (95% CI, 0.21-0.36), respectively. Combined, velamentous and marginal cord insertions were not significantly associated with TTTS twins requiring laser (p = 0.72, p = 0.38, and p = 0.71, respectively) versus non-TTTS monochorionic twins.

CONCLUSIONS

To the best of our knowledge, this is the first review to conjointly explore outcomes of residual anastomoses and abnormal cord insertions within TTTS twins following laser. A large prospective study is necessitated to assess the relationship between abnormal cord insertion and residual anastomoses development post-laser.

Learning-based keypoint registration for fetoscopic mosaicking

PURPOSE

In twin-to-twin transfusion syndrome (TTTS), abnormal vascular anastomoses in the monochorionic placenta can produce uneven blood flow between the two fetuses. In the current practice, TTTS is treated surgically by closing abnormal anastomoses using laser ablation. This surgery is minimally invasive and relies on fetoscopy. Limited field of view makes anastomosis identification a challenging task for the surgeon.

METHODS

To tackle this challenge, we propose a learning-based framework for in vivo fetoscopy frame registration for field-of-view expansion. The novelties of this framework rely on a learning-based keypoint proposal network and an encoding strategy to filter (i) irrelevant keypoints based on fetoscopic semantic image segmentation and (ii) inconsistent homographies.

RESULTS

We validate our framework on a dataset of six intraoperative sequences from six TTTS surgeries from six different women against the most recent state-of-the-art algorithm, which relies on the segmentation of placenta vessels.

CONCLUSION

The proposed framework achieves higher performance compared to the state of the art, paving the way for robust mosaicking to provide surgeons with context awareness during TTTS surgery.

Placental vessel segmentation and registration in fetoscopy: Literature review and MICCAI FetReg2021 challenge findings

Fetoscopy laser photocoagulation is a widely adopted procedure for treating Twin-to-Twin Transfusion Syndrome (TTTS). The procedure involves photocoagulation pathological anastomoses to restore a physiological blood exchange among twins. The procedure is particularly challenging, from the surgeon's side, due to the limited field of view, poor manoeuvrability of the fetoscope, poor visibility due to amniotic fluid turbidity, and variability in illumination. These challenges may lead to increased surgery time and incomplete ablation of pathological anastomoses, resulting in persistent TTTS. Computer-assisted intervention (CAI) can provide TTTS surgeons with decision support and context awareness by identifying key structures in the scene and expanding the fetoscopic field of view through video mosaicking. Research in this domain has been hampered by the lack of high-quality data to design, develop and test CAI algorithms. Through the Fetoscopic Placental Vessel Segmentation and Registration (FetReg2021) challenge, which was organized as part of the MICCAI2021 Endoscopic Vision (EndoVis) challenge, we released the first large-scale multi-center TTTS dataset for the development of generalized and robust semantic segmentation and video mosaicking algorithms with a focus on creating drift-free mosaics from long duration fetoscopy videos. For this challenge, we released a dataset of 2060 images, pixel-annotated for vessels, tool, fetus and background classes, from 18 in-vivo TTTS fetoscopy procedures and 18 short video clips of an average length of 411 frames for developing placental scene segmentation and frame registration for mosaicking techniques. Seven teams participated in this challenge and their model performance was assessed on an unseen test dataset of 658 pixel-annotated images from 6 fetoscopic procedures and 6 short clips. For the segmentation task, overall baseline performed was the top performing (aggregated mIoU of 0.6763) and was the best on the vessel class (mIoU of 0.5817) while team RREB was the best on the tool (mIoU of 0.6335) and fetus (mIoU of 0.5178) classes. For the registration task, overall the baseline performed better than team SANO with an overall mean 5-frame SSIM of 0.9348. Qualitatively, it was observed that team SANO performed better in planar scenarios, while baseline was better in non-planner scenarios. The detailed analysis showed that no single team outperformed on all 6 test fetoscopic videos. The challenge provided an opportunity to create generalized solutions for fetoscopic scene understanding and mosaicking. In this paper, we present the findings of the FetReg2021 challenge, alongside reporting a detailed literature review for CAI in TTTS fetoscopy. Through this challenge, its analysis and the release of multi-center fetoscopic data, we provide a benchmark for future research in this field.

Twin Anemia-Polycythemia Sequence (TAPS): From Basic Research to Clinical Practice

Twin pregnancy is associated with an increased risk of perinatal and maternal complications, and early establishment of the chorionicity type defines this risk. In monochorionic (MC) pregnancies, the fetuses share the same placental mass and exhibit vascular anastomoses crossing the intertwin membrane, and the combination and pattern of anastomoses determine the primary clinical picture and occurrence of future complications. Twin Anemia-Polycythemia Sequence (TAPS) was first described in 2006 after fetoscopic laser surgery in twin-to-twin transfusion syndrome (TTTS) twins, and in 2007, the first spontaneous cases were reported, recognizing TAPS as an individualized vascular identity in fetofetal transfusion syndromes. There are two types of TAPS: spontaneous (3-5%) and iatrogenic or postlaser (2-16%). TAPS consists of small diameter arteriovenous anastomoses (<1 mm) and low-rate, small-caliber AA anastomoses in the absence of amniotic fluid discordances. There are certain antenatal and postnatal diagnostic criteria, which have progressively evolved over time. New, additional secondary markers have been proposed, and their reliability is being studied. The best screening protocol for TAPS in MC twins is still a matter of debate. This review provides a survey of the relevant literature on the epidemiology, vascular pathophysiology, underlying hemodynamic factors that regulate mismatched vascular connections, and diagnostic criteria of this condition. The aim is to increase awareness and knowledge about this recently identified and frequently unrecognized and misdiagnosed pathology.

Robust fetoscopic mosaicking from deep learned flow fields

PURPOSE

Fetoscopic laser photocoagulation is a minimally invasive procedure to treat twin-to-twin transfusion syndrome during pregnancy by stopping irregular blood flow in the placenta. Building an image mosaic of the placenta and its network of vessels could assist surgeons to navigate in the challenging fetoscopic environment during the procedure.

METHODOLOGY

We propose a fetoscopic mosaicking approach by combining deep learning-based optical flow with robust estimation for filtering inconsistent motions that occurs due to floating particles and specularities. While the current state of the art for fetoscopic mosaicking relies on clearly visible vessels for registration, our approach overcomes this limitation by considering the motion of all consistent pixels within consecutive frames. We also overcome the challenges in applying off-the-shelf optical flow to fetoscopic mosaicking through the use of robust estimation and local refinement.

RESULTS

We compare our proposed method against the state-of-the-art vessel-based and optical flow-based image registration methods, and robust estimation alternatives. We also compare our proposed pipeline using different optical flow and robust estimation alternatives.

CONCLUSIONS

Through analysis of our results, we show that our method outperforms both the vessel-based state of the art and LK, noticeably when vessels are either poorly visible or too thin to be reliably identified. Our approach is thus able to build consistent placental vessel mosaics in challenging cases where currently available alternatives fail.

Selective vs complete fetoscopic coagulation of vascular equator: a matched comparative study

BACKGROUND

Complete coagulation of the vascular equator (as in the Solomon technique) has been suggested to reduce postoperative complications such as twin anemia polycythemia syndrome and the recurrence of twin-twin transfusion syndrome following fetoscopic laser coagulation of chorionic vessels for twin-twin transfusion syndrome.

OBJECTIVE

We aimed to evaluate the benefit of this technique on perinatal outcomes compared with selective ablation of anastomoses.

STUDY DESIGN

We conducted a monocentric retrospective study comparing selective laser coagulation of anastomoses to the Solomon technique from January 2006 to August 2020. To adjust for potential confounders, the cases operated by selective surgery were matched to the cases operated with the Solomon technique according to the gestational age at laser therapy, placental localization, and Quintero stage using propensity score matching.

RESULTS

With a total of 994 cases, 399 matched pairs were included in the analysis. Compared with selective ablation, the Solomon technique was associated with significantly improved survival: the overall twin survival at delivery and discharge was 72% vs 79% (P=.003) and 69% vs 75% (P=.006), respectively; the double twin survival rate at discharge was 55% vs 65% (P=.02), respectively, and the rate of intrauterine death dropped from 18% to 12% (P=.003), respectively. The Solomon technique significantly reduced the rate of twin anemia polycythemia syndrome (10% vs 4%; P=.02), leading to fewer secondary rescue procedures (13% vs 7.3%; P=.01). However, the Solomon technique was associated with an increased risk of preterm rupture of membranes, especially at early gestational ages (3.8% vs 11%; P<.001 for preterm rupture of membranes <24 weeks). Among the survivors at delivery, both the groups had similar gestational ages at birth. Both neonatal mortality and severe neurologic morbidity were similar in both the groups. However, an increased risk of bronchopulmonary dysplasia was found in the Solomon group (4.5% vs 12%; P<.001).

CONCLUSION

Although the risk of preterm premature rupture of membranes has increased, the introduction of the Solomon technique has significantly improved perinatal outcomes in pregnancies affected with twin-twin transfusion syndrome.

Twin-to-twin transfusion syndrome: Controversies in the diagnosis and management

In twin-to-twin transfusion syndrome (TTTS) communicating placental vessels on the chorionic plate between the donor and recipient twins are responsible for the chronic imbalance of blood flow. Evidence demonstrates that fetoscopic laser ablation is superior to serial amnioreductions in terms of survival and neurological outcome for stages II-IV TTTS. However, the optimal management of stage I TTTS remains poorly understood. It is well established that all chorionic plate anastomoses should be closed by laser ablation. Compared to the selective laser method, the Solomon technique yields a significant reduction of recurrent TTTS and post-laser twin anemia polycythemia sequence (TAPS). Over the past 25 years, survival rates after fetoscopic laser surgery have significantly increased. High volume centers report up to 70% double survival and at least one survivor in >90% cases. In this review, we discuss the controversies in the diagnosis and management of TTTS, especially, the optimal management in stage I cases, very early or late diagnosis, and the optimal laser technique. Furthermore, we will discuss a stage-related outcome after laser surgery and examine whether it is necessary at all to distinguish between stages I and II. Finally, the optimal timing as well as mode of delivery after TTTS laser treatment will be discussed.

Risk Profiling of the Solomon Technique versus Selective Technique of Fetoscopic Laser Surgery for Twin-Twin Transfusion Syndrome

We evaluated the outcomes and adverse events after fetoscopic laser surgery (FLS) for twin-twin transfusion syndrome (TTTS) using the Solomon technique in comparison to the selective technique. A retrospective analysis of a single-center consecutive cohort of FLS-treated TTTS using the selective (January 2010 to July 2014) and Solomon (August 2014 to December 2017) techniques was performed. Among 395 cases, 227 underwent selective coagulation and 168 underwent the Solomon technique. The incidence rates of recurrent TTTS (Solomon vs. selective: 0% vs. .9%, p = .510) and twin anemia-polycythemia sequence (.6% vs. .4%, p = .670) were very low in both groups. The incidence rates of placental abruption (Solomon vs. selective: 10.7% vs. 3.5%, p = .007) and preterm premature rupture of the membranes (pPROM) with subsequent delivery before 32 weeks (20.2% vs. 7.1%, p < .001) were higher in the Solomon group. The median birth recipient weight was significantly smaller in the Solomon group (1790 g vs. 1933 g, p = .049). The rate of survival of at least one twin was significantly higher in the Solomon group (98.2% vs. 93.8%, p = .046). The Solomon technique and total laser energy were significant risk factors for pPROM (odds ratio: 2.64, 1.07, 95% CI [1.32, 5.28], [1.01, 1.13], p = .006, p = .014, respectively). These findings suggest that the Solomon technique led to superior survival outcomes but increased risks of placental abruption, pPROM and fetal growth impairment. Total laser energy was associated with the occurrence of pPROM. Close attention to adverse events is required for perinatal management after FLS to treat TTTS using the Solomon technique.

Placental Anatomy and Function in Twin Gestations

With an increasing incidence of twin gestations, understanding the inherent risks associated with these pregnancies is essential in modern obstetrics. The unique differences in placentation in twins contribute to the increased risks. Monochorionic twins are susceptible to complications because of their unique placental architecture, including twin-to-twin transfusion syndrome, the twin anemia-polycythemia sequence, selective intrauterine growth restriction, and the twin reversed arterial perfusion sequence. Knowing the clinical correlations of placental anatomy in these gestations helps perinatal pathologists perform a more informed placental evaluation, allowing for better care for the mother and her children.

Complex Method of CT and Morphological Examination of Placental Angioarchitechtonics

We propose an original method of complex assessment of the placental angioarchitechtonics based on computed tomography (CT) and morphological examination. A prerequisite condition of successful examination and assessment of the placental angioarchitechtonics is the pre-preparative stage including clearing of the placental and umbilical cord vessels from blood clots by placement of placenta into 10% hypertonic NaCl solution and then on a hygroscopic substrate. The major stage of this method is injection of contrast staining mixtures into the umbilical vessels followed by CT. The concentration of radiocontrast agent in water solution of gouache should be 70% for arteries and 15% for veins. The volumes of mixtures for contrast staining should be calculated according to the weight of the placenta. The contrast staining mixture was first injected into the catheterized unpaired umbilical vein, and then into both umbilical arteries. Each injection of the contrast staining mixture was visually inspected; then branching of the stained vessel was photographed and scanned by CT. The CT scans were used to construct 3D models of placental vessels and spectral color maps, which made it possible to examine the peculiarities of placental angioarchitechtonics, to identify and evaluate anastomoses of placental vessels, and to establish the type of these anastomoses.

US Evaluation of Twin Pregnancies: Importance of Chorionicity and Amnionicity

The twin birth rate is increasing in the United States. Twin pregnancies can be dichorionic or monochorionic (MC). MC twins account for 20% of twin pregnancies but 30% of all-cause pregnancy-related complications. This article describes the imaging findings that establish chorionicity and amnionicity. Ideally, these are established in the first trimester when accuracy is high, but they can also be determined later in pregnancy. Complications unique to MC twin pregnancy include twin-twin transfusion syndrome, twin anemia polycythemia sequence, twin reversed arterial perfusion sequence, and selective fetal growth restriction. The US features, staging systems, and management of these complications are reviewed, and the consequences of MC twin demise are illustrated. Ongoing surveillance for these conditions starts at 16 weeks gestation. Monoamniotic (MA) twins are a small subset of MC twins. In addition to all of the MC complications, specific MA complications include cord entanglement and conjoined twinning. Radiologists must be able to determine chorionicity and amnionicity and should be aware of potential complications so that patients may be referred to appropriate regional specialized centers. A proposed algorithm for referral to specialized fetal treatment centers is outlined. Online supplemental material is available for this article. ^©RSNA, 2019.

Middle Cerebral Artery Doppler Velocimetry for the Diagnosis of Twin Anemia Polycythemia Sequence: A Systematic Review

Twin anemia polycythemia sequence (TAPS) is a rare complication of monochorionic diamniotic (MCDA) twins. Middle cerebral artery peak systolic velocity (MCA-PSV) measurements are used to screen for TAPS while fetal or neonatal hemoglobin levels are required for definitive diagnosis. We sought to perform a systematic review of the efficacy of MCA-PSV in diagnosing TAPS. Search criteria were developed using relevant terms to query the Pubmed, Embase, and SCOPUS electronic databases. Publications reporting diagnostic characteristics of MCA-PSV measurements (i.e., sensitivity, specificity or receiver operator curves) were included. Each article was assessed for bias using the Quality Assessment of Diagnostic Accuracy Studies II (QUADAS II) tool. Results were assessed for uniformity to determine whether meta-analysis was feasible. Data were presented in tabular form. Among publications, five met the inclusion criteria. QUADAS II analysis revealed that four of the publications were highly likely to have bias in multiple areas. Meta-analysis was precluded by non-uniformity between definitions of TAPS by MCA-PSV and neonatal or fetal hemoglobin levels. High-quality prospective studies with consistent definitions and ultrasound surveillance protocols are still required to determine the efficacy of MCA-PSV in diagnosing TAPS. Other ultrasound findings (e.g., placenta echogenicity discordance) may augment Doppler studies.

FetNet: a recurrent convolutional network for occlusion identification in fetoscopic videos

PURPOSE

Fetoscopic laser photocoagulation is a minimally invasive surgery for the treatment of twin-to-twin transfusion syndrome (TTTS). By using a lens/fibre-optic scope, inserted into the amniotic cavity, the abnormal placental vascular anastomoses are identified and ablated to regulate blood flow to both fetuses. Limited field-of-view, occlusions due to fetus presence and low visibility make it difficult to identify all vascular anastomoses. Automatic computer-assisted techniques may provide better understanding of the anatomical structure during surgery for risk-free laser photocoagulation and may facilitate in improving mosaics from fetoscopic videos.

METHODS

We propose FetNet, a combined convolutional neural network (CNN) and long short-term memory (LSTM) recurrent neural network architecture for the spatio-temporal identification of fetoscopic events. We adapt an existing CNN architecture for spatial feature extraction and integrated it with the LSTM network for end-to-end spatio-temporal inference. We introduce differential learning rates during the model training to effectively utilising the pre-trained CNN weights. This may support computer-assisted interventions (CAI) during fetoscopic laser photocoagulation.

RESULTS

We perform quantitative evaluation of our method using 7 in vivo fetoscopic videos captured from different human TTTS cases. The total duration of these videos was 5551 s (138,780 frames). To test the robustness of the proposed approach, we perform 7-fold cross-validation where each video is treated as a hold-out or test set and training is performed using the remaining videos.

CONCLUSION

FetNet achieved superior performance compared to the existing CNN-based methods and provided improved inference because of the spatio-temporal information modelling. Online testing of FetNet, using a Tesla V100-DGXS-32GB GPU, achieved a frame rate of 114 fps. These results show that our method could potentially provide a real-time solution for CAI and automating occlusion and photocoagulation identification during fetoscopic procedures.

Photoacoustic imaging of the human placental vasculature

Minimally invasive fetal interventions require accurate imaging from inside the uterine cavity. Twin-to-twin transfusion syndrome (TTTS), a condition considered in this study, occurs from abnormal vascular anastomoses in the placenta that allow blood to flow unevenly between the fetuses. Currently, TTTS is treated fetoscopically by identifying the anastomosing vessels, and then performing laser photocoagulation. However, white light fetoscopy provides limited visibility of placental vasculature, which can lead to missed anastomoses or incomplete photocoagulation. Photoacoustic (PA) imaging is an alternative imaging method that provides contrast for hemoglobin, and in this study, two PA systems were used to visualize chorionic (fetal) superficial and subsurface vasculature in human placentas. The first system comprised an optical parametric oscillator for PA excitation and a 2D Fabry-Pérot cavity ultrasound sensor; the second, light emitting diode arrays and a 1D clinical linear-array ultrasound imaging probe. Volumetric photoacoustic images were acquired from ex vivo normal term and TTTS-treated placentas. It was shown that superficial and subsurface branching blood vessels could be visualized to depths of approximately 7 mm, and that ablated tissue yielded negative image contrast. This study demonstrated the strong potential of PA imaging to guide minimally invasive fetal therapies.

Twin-twin transfusion syndrome in the era of fetoscopic laser surgery: antenatal management, neonatal outcome and beyond

Introduction: Twin-twin transfusion syndrome (TTTS) is a devastating complication of monochorionic twin pregnancy and remains a major challenge for worldwide fetal medicine specialists. In TTTS, intertwin transfusion through vascular anastomoses in the shared placenta leads to severe hemodynamic imbalance. This review summarizes the current knowledge of TTTS.Areas covered: The most recent insights concerning the management of TTTS, as well as fetal and neonatal complications are described. Relevant articles were selected based on a Pubmed search using the keywords below. Understanding of the underlying pathophysiology has improved greatly as a result of placental injection studies. Advancements in antenatal management have led to increased perinatal survival and a decreased incidence of neonatal complications, including brain injury and neurodevelopmental impairment.Expert opinion: Further opportunities for improvement comprise technological innovations in laser procedures and the prevention of preterm rupture of membranes with subsequent prematurity. A noninvasive treatment such as high-intensity focused ultrasound (HIFU) seems to hold promise for the future treatment of TTTS. Fetal MRI studies are important to improve our understanding of fetal brain injury and should relate their findings to long-term neurodevelopment. International collaboration and centralization of care are of paramount importance to ensure the best care for our patients.

Complex multigestational anomalies

The increase in multiple gestation pregnancies has resulted in significant health care implications for both mother and child. Our ability to diagnose and intervene on an at-risk multi-gestation pregnancy has dramatically improved. It is important for the pediatric surgeon to be equipped with a basic fund of knowledge concerning these pregnancies. An understanding of amnionicity and chorionicity will equip the practitioner with the ability to identify which pregnancies are at risk for specific complications. This article highlights multi-gestation pregnancies that are monochorionic (single shared placenta) and can be complicated by twin-twin transfusion syndrome (TTTS), twin reversed arterial perfusion (TRAP) sequence, twin anemia polycythemia sequence (TAPS), or selective fetal intrauterine growth restriction (sIUGR). The risk of fetal demise is significant in these pregnancies. Understanding recommended surveillance and warning signs can alert surgeons to developing complications. Specialized fetal care centers possess the ability to intervene on these pregnancies in utero.

Influence of maternal obesity and metabolic and vascular mediators in twin-twin transfusion syndrome

Obesity is a risk factor for complications in singleton and twin pregnancies; however, there are limited data regarding maternal body mass index (BMI) in the setting of twin-twin transfusion syndrome (TTTS). We hypothesized that increased BMI in TTTS is associated with adverse perinatal outcomes and vascular pathology. A retrospective study of twin reversed arterial perfusion (n = 4), selective intrauterine growth restriction (n = 10) and TTTS (n = 33) was conducted. Treatment included fetoscopic laser photocoagulation (FLP) (n = 35) or Solomon technique (n = 12). Ex vivo placental intravascular injections, immunohistochemistry, and perinatal outcomes were compared by maternal BMI. In pregnancy complicated by TTTS, 16/33 women were obese (BMI > 30 kg/m²) and 11/33 were overweight (BMI 25-29.9 kg/m²). Women who were overweight or obese had an increased rate of premature rupture of membranes (PPROM), cesarean delivery, and/or concomitant co-morbidities when compared to the normal weight group. Duration of neonatal intensive care unit (NICU) admission was longer in neonates of overweight/obese women versus normal weight. Placental examination of FLP sites in the obese group showed larger infarcts, increased adipose triglyceride lipase, and a proangiogenic phenotype. Increased BMI is common in our TTTS cohort and it is associated with higher rate of co-morbidity, PPROM, prolonged NICU stay, and an imbalance of placental metabolic and vascular mediators.

Modified fetoscopic laser surgery in twin-to-twin transfusion syndrome with proximate cord insertions: a report of two cases and literature review

Proximate cord insertions (PxCIs) are a variant of umbilical cord insertions (CIs) that can be identified in monochorionic (MC) twins, making fetoscopic laser photocoagulation for twin-to-twin transfusion syndrome (TTTS) technically challenging. The existing literature is controversial for successful fetoscopic laser photocoagulation in TTTS cases with PxCIs. We presented two cases with TTTS complicated by PxCIs that underwent a successful laser ablation using our proposed technique.

Update on twin-to-twin transfusion syndrome

Twin-to-twin transfusion syndrome (TTTS) is a serious complication that affects 10-15% of monochorionic multiple pregnancies. Communicating placental vessels on the chorionic plate between the donor and recipient twin are responsible for the imbalance of blood flow. There is evidence for the superiority of fetoscopic laser ablation over serial amnioreductions regarding survival and neurological outcome for stages II-IV TTTS. However, the optimal management of stage I is still debated. The "Solomon" technique showed a significant reduction in recurrent TTTS and post laser twin anemia-polycythemia sequence (TAPS) in comparison to the selective laser method without improvement in perinatal mortality or neonatal morbidity. Survival rates after fetoscopic laser surgery have significantly increased over the last 25 years. High volume centers report up to 70% double survival and at least one survivor in >90%. Long-term neurodevelopmental impairment occurs in about 10% of children after laser surgery. In this review we discuss the optimal management, innovations in laser technique, long-term neurodevelopmental outcome, and future aspects of TTTS treatment.

Retrieval and registration of long-range overlapping frames for scalable mosaicking of in vivo fetoscopy

Purpose

The standard clinical treatment of Twin-to-Twin transfusion syndrome consists in the photo-coagulation of undesired anastomoses located on the placenta which are responsible to a blood transfer between the two twins. While being the standard of care procedure, fetoscopy suffers from a limited field-of-view of the placenta resulting in missed anastomoses. To facilitate the task of the clinician, building a global map of the placenta providing a larger overview of the vascular network is highly desired.

Methods

To overcome the challenging visual conditions inherent to in vivo sequences (low contrast, obstructions or presence of artifacts, among others), we propose the following contributions: (1) robust pairwise registration is achieved by aligning the orientation of the image gradients, and (2) difficulties regarding long-range consistency (e.g. due to the presence of outliers) is tackled via a bag-of-word strategy, which identifies overlapping frames of the sequence to be registered regardless of their respective location in time.

Results

In addition to visual difficulties, in vivo sequences are characterised by the intrinsic absence of gold standard. We present mosaics motivating qualitatively our methodological choices and demonstrating their promising aspect. We also demonstrate semi-quantitatively, via visual inspection of registration results, the efficacy of our registration approach in comparison with two standard baselines.

Conclusion

This paper proposes the first approach for the construction of mosaics of placenta in in vivo fetoscopy sequences. Robustness to visual challenges during registration and long-range temporal consistency are proposed, offering first positive results on in vivo data for which standard mosaicking techniques are not applicable.

Electronic supplementary material

The online version of this article (10.1007/s11548-018-1728-4) contains supplementary material, which is available to authorized users.

Solomon Technique Versus Selective Coagulation for Twin-Twin Transfusion Syndrome

Monochorionic twin pregnancies can be complicated by twin-to-twin transfusion syndrome (TTTS). The best treatment option for TTTS is fetoscopic laser coagulation of the vascular anastomoses between donor and recipient. After laser therapy, up to 33% residual anastomoses were seen. These residual anastomoses can cause twin anemia polycythemia sequence (TAPS) and recurrent TTTS. In order to reduce the number of residual anastomoses and their complications, a new technique, the Solomon technique, where the whole vascular equator will be coagulated, was introduced. The Solomon technique showed a reduction of recurrent TTS compared to the selective technique. The incidence of recurrent TTTS after the Solomon technique ranged from 0% to 3.9% compared to 5.3-8.5% after the selective technique. The incidence of TAPS after the Solomon technique ranged from 0% to 2.9% compared to 4.2-15.6% after the selective technique. The Solomon technique may improve dual survival rates ranging from 64% to 85% compared to 46-76% for the selective technique. There was no difference reported in procedure-related complications such as intrauterine infection and preterm premature rupture of membranes. The Solomon technique significantly reduced the incidence of TAPS and recurrent TTTS and may improve survival and neonatal outcome, without identifiable adverse outcome or complications; therefore, the Solomon technique is recommended for the treatment of TTTS.

Hematological disorders at birth in complicated monochorionic twins

INTRODUCTION

Monochorionic twins are at risk of severe complications including twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS) and acute peripartum TTTS. The pathophysiology is based on inter-twin blood transfusion through placental vascular anastomoses. Areas covered: This review focuses on the incidence, management and outcome of neonatal hematological complications at birth in TTTS, TAPS and acute peripartum TTTS. Expert commentary: Hematological disorders are often present at birth in monochorionic twins and include acute or chronic anemia, polycythemia and thrombocytopenia. Routine measurement of complete blood counts in all complicated monochorionic twins is strongly recommended. Increased awareness on these disorders and correct diagnostic tests will lead to prompt and adequate management at birth.

Laser Treatment of Twin–to–Twin Transfusion Syndrome

Objective: Laser ablation of all placental vascular anastomoses is the optimal treatment for twin–twin transfusion syndrome (TTTS). However, two important controversies are apparent in the literature: (a) a gap between concept and performance, and (b) controversy regarding whether all the anastomoses can be identified endoscopically and whether blind lasering of healthy placenta is justified. The purpose of this article is: (a) to address the potential source of the gap between concept and performance by analyzing the fundamental steps needed to successfully accomplish the surgery, and (b) to discuss the resulting competency benchmarks reported with the different surgical techniques. Materials and Methods: Laser surgery for TTTS can be broken down into two fundamental steps: (1) endoscopic identification of the placental vascular anastomoses, (2) laser ablation of the anastomoses. The two steps are not synonymous: (a) regarding the endoscopic identification of the anastomoses, the non-selective technique is based upon lasering all vessels crossing the dividing membrane, whether anastomotic or not. The selective technique identifies and lasers only placental vascular anastomoses. The Solomon technique is based on the theory that not all anastomoses are endoscopically visible and thus involves lasering healthy areas of the placenta between lasered anastomoses, (b) regarding the actual laser ablation of the anastomoses, successful completion of the surgery (i.e., lasering all the anastomoses) can be measured by the rate of persistent or reverse TTTS (PRTTTS) and how often a selective technique can be achieved. Articles representing the different techniques are discussed. Results: The non-selective technique is associated with the lowest double survival rate (35%), compared with 60–75% of the Solomon or the Quintero selective techniques. The Solomon technique is associated with a 20% rate of residual patent placental vascular anastomoses, compared to 3.5–5% for the selective technique (p < .05). Both the Solomon and the selective technique are associated with a 1% risk of PRTTTS. Adequate placental assessment is highest with the selective technique (99%) compared with the Solomon (80%) or the ‘standard’ (60%) techniques (p < .05). A surgical performance index is proposed. Conclusion: The Quintero selective technique was associated with the highest rate of successful ablation and lowest rate of PRTTTS. The Solomon technique represents a historical backward movement in the identification of placental vascular anastomoses and is associated with higher rate of residual patent vascular communications. The reported outcomes of the Quintero selective technique do not lend support to the existence of invisible anastomoses or justify lasering healthy placental tissue.

Neurodevelopmental outcome at 2 years in twin-twin transfusion syndrome survivors randomized for the Solomon trial

BACKGROUND

The preferred treatment for twin-twin transfusion syndrome is fetoscopic laser coagulation of inter-twin vascular anastomoses on the monochorionic placenta. Severe postoperative complications can occur when inter-twin vascular anastomoses remain patent including twin-anemia polycythemia sequence or recurrent twin-twin transfusion syndrome. To minimize the occurrence of residual anastomoses, a modified laser surgery technique, the Solomon technique, was developed in which the entire vascular equator is coagulated. In the Solomon randomized controlled trial (NTR1245), the Solomon technique was associated with a significant reduction in twin-anemia polycythemia sequence and recurrence of twin-twin transfusion syndrome when compared with the standard laser surgery technique. Although a significant improvement in perinatal outcome was shown after the Solomon technique, the clinical importance should also be ascertained with long-term follow-up evaluation of the surviving children.

OBJECTIVE

The purpose of this study was to compare the long-term neurodevelopmental outcome in surviving children with twin-twin transfusion syndrome who were included in the Solomon randomized trial and treated with either the Solomon technique or standard laser surgery technique.

STUDY DESIGN

Routine standardized follow-up evaluation in survivors, at least 2 years after the estimated date of delivery, was performed at 2 of the 5 centers that participated in the Solomon trial: Buzzi Hospital Milan (Italy) and Leiden University Medical Center (The Netherlands). The primary outcome of this follow-up study was survival without long-term neurodevelopmental impairment at age 2 years. Neurodevelopmental impairment was defined as cerebral palsy, cognitive and/or motor development score of <85, bilateral blindness, or deafness. Cognitive and motor development was evaluated with the use of Bayley-III. All analyses per fetus, neonate, or child were conducted with the generalized estimated equation module to account for the effect that observations between co-twins are not independent.

RESULTS

The primary outcome (survival without neurodevelopmental impairment) was detected in 95 of 141 cases (67%) in the Solomon group and in 99 of 146 cases (68%) in the standard group (P = .92). Neurodevelopmental impairment in long-term survivors who were included for follow-up evaluation was detected in 12 of 107 cases (11%) in the Solomon and in 10 of 109 cases (9%) in the standard group (P = .61). Neurodevelopmental impairment was due to cerebral palsy in 1 case (1%; spastic unilateral) in the Solomon group and in 2 cases (2%; spastic unilateral and spastic bilateral) in the standard group (P = .58). Cognitive development <85 cases was detected in 2 of 105 children (2%) in the Solomon group and in 6 of 106 children (6%) in the standard group (P = .23). Motor development <85 occurred in 8 of 103 children (8%) in the Solomon group and 3 of 104 children (3%) in the standard group (P = .23).

CONCLUSION

We found no difference in survival without neurodevelopmental impairment between the Solomon and standard laser techniques. In view of the reduction of short-term complications and the absence of increased adverse long-term effects, these data support the use of the Solomon technique in the treatment of twin-twin transfusion syndrome.

The North American Fetal Therapy Network Consensus Statement: Management of Complicated Monochorionic Gestations

The North American Fetal Therapy Network is a consortium of 30 medical institutions in the United States and Canada with established expertise in fetal therapy and other forms of multidisciplinary care for complex fetal disorders. This publication is the third in a series of articles written by NAFTNet about monochorionic pregnancies. In this article, we provide the general obstetric practitioner with information regarding management options available for complications of monochorionic gestations. This information may be useful for a better understanding of the pathophysiology of the various conditions, for better patient counseling, for timely referral to a regional treatment center, and for ongoing comanagement after treatment.

The North American Fetal Therapy Network consensus statement: prenatal surveillance of uncomplicated monochorionic gestations

Because they share a common placenta, monochorionic gestations are subject to unique pregnancy complications that can threaten the life and health of both fetuses and therefore impose a disproportionate disease burden on overall perinatal morbidity and mortality. Early detection of these unique disease processes may allow for prompt referral to a regional treatment center, comprehensive counseling, and better patient outcomes. The North American Fetal Therapy Network is a consortium of 30 medical institutions in the United States and Canada with established expertise in fetal surgery and other forms of multidisciplinary care for complex fetal disorders. The goal of this publication is to briefly describe complications of monochorionic gestations and to provide multidisciplinary, evidence-based, and consensus-driven recommendations for surveillance of uncomplicated monochorionic gestations.

Iatrogenic perforation of intertwin membrane after laser surgery for twin-to-twin transfusion syndrome

OBJECTIVE

To evaluate management and outcome of iatrogenic monoamniotic twins (iMAT) compared with twins with intact intertwin dividing membranes after laser surgery for twin-to-twin transfusion syndrome (TTTS).

METHODS

This was a retrospective analysis of twins with and without iatrogenic rupture of the intertwin membranes that had been treated for TTTS with laser surgery at our center between 2004 and 2012. Primary outcomes were perinatal survival and severe neonatal morbidity. Secondary outcomes were mode of delivery, gestational age at birth and cord entanglement.

RESULTS

In total, 338 pregnancies were included. In 67/338 (20%) pregnancies, iMAT was suspected antenatally. In 47 of these 67 (70%), a preterm Cesarean section was performed for monoamnionicity. Perinatal survival was 108/134 (81%) vs 396/542 (73%) in twins with intact intertwin membranes (P = 0.13). Mean gestational age at birth in iMAT was 31 completed weeks, compared to 33 weeks in twins with intact membranes (P < 0.01). At birth, cord entanglement was present in 8/67 (12%) iMAT pregnancies. Severe neonatal morbidity was assessed in 106/110 (96%) in iMAT cases and 392/416 (94%) in controls. The incidence of severe neonatal morbidity was 28/106 (26%) in iMAT vs 72/392 (18%) in controls (P = 0.25). Severe cerebral injury was significantly increased in the iMAT group as compared with controls, at 16/106 (15%) vs 18/392 (5%) (P < 0.01).

CONCLUSIONS

Iatrogenic rupture of intertwin membranes was suspected in 20% of pregnancies treated with laser therapy for TTTS and was associated with a lower gestational age at birth and increased neonatal morbidity.

Predictive value of cardiovascular parameters in twin-to-twin transfusion syndrome

OBJECTIVE

To evaluate the prognostic value of the Children's Hospital Of Philadelphia (CHOP) cardiovascular score and the modified myocardial performance index (MPI), in determining the risk of recipient fetal loss in twin-to-twin transfusion syndrome (TTTS).

METHODS

This cohort study was based on data collected prospectively from 105 pregnancies complicated by TTTS (Quintero stages I-IV) and treated with laser photocoagulation between May 2008 and February 2013. Fetuses underwent detailed anatomical and Doppler ultrasonography with cardiac assessment as part of routine care. CHOP score and right MPI were calculated and cut-offs selected using receiver-operating characteristics curve analysis. These were compared according to loss of recipient fetus, using univariate and multivariate logistic regression. The correlation between CHOP score, MPI and Quintero stage was determined and we investigated differences in MPI before and after laser coagulation in a cohort of 90 recipient fetuses.

RESULTS

Rates of recipient fetal loss were significantly higher when the CHOP score was ≥ 3 (39.5% vs 12.9%, P = 0.002) and when MPI z-score was > 1.645 (34.5% vs 10.6%, P = 0.004). After adjustment for Quintero stage, the risk of recipient fetal loss remained significantly higher when the CHOP score was ≥ 3 (odds ratio, 3.09; 95% CI, 1.035-9.21). There was a positive correlation between CHOP score, MPI and Quintero stage. MPI was significantly lower after compared with before laser coagulation.

CONCLUSION

CHOP score and MPI are predictors of recipient fetal loss in TTTS and may be used to supplement Quintero's classification.

Residual anastomoses in twin-twin transfusion syndrome after laser: the Solomon randomized trial

OBJECTIVE

Residual anastomoses after fetoscopic laser surgery for twin-to-twin transfusion syndrome (TTTS) may lead to severe postoperative complications, including recurrent TTTS and twin anemia-polycythemia sequence (TAPS). A novel technique (Solomon technique) using laser coagulation of the entire vascular equator was recently investigated in a randomized controlled trial (Solomon trial) and compared with the Standard selective laser technique. The aim of this secondary analysis was to evaluate the occurrence and characteristics of residual anastomoses in placentas included in the Solomon trial.

STUDY DESIGN

International multicenter randomized controlled trial in TTTS, randomized 1:1 ratio to either the Solomon laser technique or Standard laser technique. At time of laser, surgeons recorded whether they considered the procedure to be complete. Placental dye injection was performed after birth in the participating centers to evaluate the presence of residual anastomoses.

RESULTS

A total of 151 placentas were included in the study. The percentage of placentas with residual anastomoses in the Solomon group and Standard group was 19% (14/74) and 34% (26/77), respectively (P = .04). The percentage of placentas with residual anastomoses in the subgroup of cases where the procedure was recorded as complete was 8/65 (12%) and 22/69 (32%) in the Solomon group and Standard group, respectively (P < .01).

CONCLUSION

The Solomon laser technique reduces the risk of residual anastomoses. However, careful follow-up remains essential also after the Solomon technique, as complete dichorionization is not always achieved.

Fetoscopic laser coagulation of the vascular equator versus selective coagulation for twin-to-twin transfusion syndrome: an open-label randomised controlled trial

BACKGROUND

Monochorionic twin pregnancies complicated by twin-to-twin transfusion syndrome are typically treated with fetoscopic laser coagulation. Postoperative complications can occur due to residual vascular anastomoses on the placenta. We aimed to assess the efficacy and safety of a novel surgery technique that uses laser coagulation of the entire vascular equator (Solomon technique).

METHODS

We undertook an open-label, international, multicentre, randomised controlled trial at five European tertiary referral centres. Women with twin-to-twin transfusion syndrome were randomly assigned by online randomisation (1:1) with permuted blocks to the Solomon technique or standard laser coagulation. The primary outcome was a composite of incidence of twin anaemia polycythaemia sequence, recurrence of twin-to-twin transfusion syndrome, perinatal mortality, or severe neonatal morbidity. Analyses were by intention to treat, with results expressed as odds ratios (ORs) and 95% CIs. This trial is registered with the Dutch Trial Registry, number NTR1245.

FINDINGS

Between March 11, 2008, and July 12, 2012, 274 women were randomly assigned to either the Solomon group (n=139) or the standard treatment group (n=135). The primary outcome occurred in 94 (34%) of 274 fetuses in the Solomon group versus 133 (49%) of 270 in the standard treatment group (OR 0·54; 95% CI 0·35-0·82). The Solomon technique was associated with a reduction in twin anaemia polycythaemia sequence (3% vs 16% for the standard treatment; OR 0·16, 95% CI 0·05-0·49) and recurrence of twin-to-twin transfusion syndrome (1% vs 7%; 0·21, 0·04-0·98). Perinatal mortality and severe neonatal morbidity did not differ significantly between the two groups. Outside of the common and well-known complications of twin-to-twin transfusion syndrome and its treatment, no serious adverse events occurred.

INTERPRETATION

Fetoscopic laser coagulation of the entire vascular equator reduces postoperative fetal morbidity in severe twin-to-twin transfusion syndrome. We recommend that fetoscopic surgeons consider adopting this strategy for treatment of women with twin-to-twin transfusion syndrome.

FUNDING

Netherlands Organization for the Health Research and Development (ZonMw 92003545).

Outcome after fetoscopic selective laser ablation of placental anastomoses vs equatorial laser dichorionization for the treatment of twin-to-twin transfusion syndrome

OBJECTIVE

The objective of the study was to compare the outcome in women with twin-twin transfusion syndrome (TTTS) who were managed by selective laser ablation of placental anastomoses (S-LASER) vs equatorial dichorionization of the anastomoses and chorionic plate (ED-LASER).

STUDY DESIGN

We conducted an analysis of 2 consecutive cohorts with TTTS treated with S-LASER and ED-LASER. Preoperative, procedural, delivery, and outcome details were compared between treatment groups.

RESULTS

A total of 147 twin pregnancies had laser (S-LASER, n = 71; ED-LASER, n = 76). Obstetric history, Quintero stage, placental location, individual arterial and venous Doppler parameters, and gestational age at laser and delivery did not differ. Use of lens fetoscope (96.1% vs 50.7%), coagulated anastomosis count (11 vs 15, P < .001), complete equatorial plate visualization (77.5% vs 92.1%, P = .019), and amniotic fluid transparency (80.3% vs 94.7%, P = .011) was greater during ED-LASER. Procedure-related complications, gestational age at delivery, and perinatal details were comparable between groups. ED-LASER was associated with significantly lower recurrence of TTTS (3.9% vs 8.5%), twin anemia polycythemia sequence (2.6% vs 4.2%), and amniotic fluid abnormalities (0% vs 5.6%, P < .05 for all comparisons). Logistic regression identified complete visualization of the equator as the primary determinant for successful TTTS treatment and coagulation of the chorionic plate as an independent cofactor. Double survival at age 6 months was significantly higher after ED-LASER (68.4% vs 50.7%, P < .05), attributable to a lower postlaser and neonatal mortality rates.

CONCLUSION

In patients with TTTS, photocoagulation of causative anastomoses and the chorionic plate along the vascular equator decreases recurrence without increasing adverse outcome and improves survival compared with the selective technique.

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.

Twin-twin transfusion syndrome

OBJECTIVE

We sought to review the natural history, pathophysiology, diagnosis, and treatment options for twin-twin transfusion syndrome (TTTS).

METHODS

A systematic review was performed using MEDLINE database, PubMed, EMBASE, and Cochrane Library. The search was restricted to English-language articles published from 1966 through July 2012. Priority was given to articles reporting original research, in particular randomized controlled trials, although review articles and commentaries also were consulted. Abstracts of research presented at symposia and scientific conferences were not considered adequate for inclusion in this document. Evidence reports and guidelines published by organizations or institutions such as the National Institutes of Health, Agency for Health Research and Quality, American College of Obstetricians and Gynecologists, and Society for Maternal-Fetal Medicine were also reviewed, and additional studies were located by reviewing bibliographies of identified articles. Consistent with US Preventive Task Force guidelines, references were evaluated for quality based on the highest level of evidence, and recommendations were graded accordingly.

RESULTS AND RECOMMENDATIONS

TTTS is a serious condition that can complicate 8-10% of twin pregnancies with monochorionic diamniotic (MCDA) placentation. The diagnosis of TTTS requires 2 criteria: (1) the presence of a MCDA pregnancy; and (2) the presence of oligohydramnios (defined as a maximal vertical pocket of <2 cm) in one sac, and of polyhydramnios (a maximal vertical pocket of >8 cm) in the other sac. The Quintero staging system appears to be a useful tool for describing the severity of TTTS in a standardized fashion. Serial sonographic evaluation should be considered for all twins with MCDA placentation, usually beginning at around 16 weeks and continuing about every 2 weeks until delivery. Screening for congenital heart disease is warranted in all monochorionic twins, in particular those complicated by TTTS. Extensive counseling should be provided to patients with pregnancies complicated by TTTS including natural history of the disease, as well as management options and their risks and benefits. The natural history of stage I TTTS is that more than three-fourths of cases remain stable or regress without invasive intervention, with perinatal survival of about 86%. Therefore, many patients with stage I TTTS may often be managed expectantly. The natural history of advanced (eg, stage ≥III) TTTS is bleak, with a reported perinatal loss rate of 70-100%, particularly when it presents <26 weeks. Fetoscopic laser photocoagulation of placental anastomoses is considered by most experts to be the best available approach for stages II, III, and IV TTTS in continuing pregnancies at <26 weeks, but the metaanalysis data show no significant survival benefit, and the long-term neurologic outcomes in the Eurofetus trial were not different than in nonlaser-treated controls. Even laser-treated TTTS is associated with a perinatal mortality rate of 30-50%, and a 5-20% chance of long-term neurologic handicap. Steroids for fetal maturation should be considered at 24 0/7 to 33 6/7 weeks, particularly in pregnancies complicated by stage ≥III TTTS, and those undergoing invasive interventions.

Twin-twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) is a serious condition that affects 10% to 15% of twin pregnancies with monochorionic diamniotic placentation. The pathophysiology of TTTS is not completely understood; however, the presence of unbalanced placental vascular communications within a shared circulation has been implicated in its development. The presentation of TTTS is highly variable, and it does not always progress in a predictable manner. Monochorionic twin gestations should, therefore, be monitored for signs of TTTS with serial sonograms starting in the second trimester. Early TTTS can be managed conservatively. However, without intervention, early-onset advanced TTTS is associated with a high perinatal loss rate and risk of severe neurologic impairment among survivors. Limited studies suggest that fetoscopic laser photocoagulation is the best available treatment for advanced TTTS diagnosed in the second trimester. Even with laser therapy, there remains a significant risk of twin demise and neurologic handicap in survivors.

Accurate and simple evaluation of vascular anastomoses in monochorionic placenta using colored dye

The presence of placental vascular anastomoses is a conditio sine qua non for the development of twin-to-twin transfusion syndrome (TTTS) and twin anemia polycythemia sequence (TAPS)(1,2). Injection studies of twin placentas have shown that such anastomoses are almost invariably present in monochorionic twins and extremely rare in dichorionic twins(1). Three types of anastomoses have been documented: from artery to artery, from vein to vein and from artery to vein. Arterio-venous (AV) anastomoses are unidirectional and are referred to as "deep" anastomoses since they proceed through a shared placental cotyledon, whereas arterio-arterial (AA) and veno-venous (VV) anastomoses are bi-directional and are referred to as "superficial" since they lie on the chorionic plate. Both TTTS and TAPS are caused by net imbalance of blood flow between the twins due to AV anastomoses. Blood from one twin (the donor) is pumped through an artery into the shared placental cotyledon and then drained through a vein into the circulation of the other twin (the recipient). Unless blood is pumped back from the recipient to the donor through oppositely directed deep AV anastomoses or through superficial anastomoses, an imbalance of blood volumes occurs, gradually leading to the development of TTTS or TAPS. The presence of an AA anastomosis has been shown to protect against the development of TTTS and TAPS by compensating for the circulatory imbalance caused by the uni-directional AV anastomoses(1,2). Injection of monochorionic placentas soon after birth is a useful mean to understand the etiology of various (hematological) complications in monochorionic twins and is a required test to reach the diagnosis of TAPS(2). In addition, injection of TTTS placentas treated with fetoscopic laser surgery allows identification of possible residual anastomoses(3-5). This additional information is of paramount importance for all perinatologists involved in the management and care of monochorionic twins with TTTS or TAPS. Several placental injection techniques are currently being used. We provide a simple protocol to accurately evaluate the presence of (residual) vascular anastomoses using colored dye injection.

Laser therapy for twin-to-twin transfusion syndrome (TTTS)

Monochorionic twins are subjected to specific complications which originate in either imbalance or abnormality of the single placenta serving two twins including twin-to-twin transfusion syndrome. The diagnosis is well established in overt clinical forms with the association of polyuric polyhydramnios and oliguric oligohydramnios. The best treatment of cases presenting before 26 weeks of gestion is fetoscopic laser ablation of the intertwin anastomoses on the chorionic plate. Although subjected to subtle variations, the core technique follows robust guidelines which could help understanding and acquiring the required skills and experience to perform this procedure. However appropriate and tailored hands-on training and appropriate perinatal set-up are critical not only for surgical management but also for the follow-up and management of related complications.

Use of the Learning Curve-Cumulative Summation test for quantitative and individualized assessment of competency of a surgical procedure in obstetrics and gynecology: fetoscopic laser ablation as a model

OBJECTIVE

We sought to determine the learning curve (LC) for fetoscopic laser photocoagulation (FLP) as a model for the evaluation of training in surgical procedures.

STUDY DESIGN

A retrospective review of consecutive case series of FLP from 2 centers with 3 operators (operator I [O-I], observer trained; operator II [O-II], hands-on trained; and operator III [O-III], clinical fellow) was performed and the LC-cumulative summation (CUSUM) test was plotted.

RESULTS

The acceptable and unacceptable success rates for at least 1 fetus survival after FLP were set at 82% and 70%, respectively, from a systematic review. A total of 171 consecutive cases were performed by the 3 operators (O-I, 91; O-II, 49; and O-III, 31). From LC-CUSUM test O-I needed 60 procedures, O-II needed 20 procedures, and O-III needed 20 procedures to reach an acceptable performance rate for at least 1 survivor.

CONCLUSION

The LC-CUSUM test can be used to accurately assess the LC in a surgical procedure in obstetrics and gynecology. Hands-on trained operators exhibit a shorter LC.

Specific complications of monochorionic twin pregnancies: twin-twin transfusion syndrome and twin reversed arterial perfusion sequence

Monochorionic twins are subjected to specific complications which originate in either imbalance or abnormality of the single placenta serving two twins. This unequal placental sharing can cause complications including twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS), selective intrauterine growth restriction or twin reversed arterial perfusion sequence (TRAP). Monochorionicity also makes the management of these specific complications as well as that of a severe malformation in one twin hazardous since the spontaneous death of one twin exposes the co-twin to a risk of exsanguination into the dead twin and its placenta. The latter is responsible for the death of the co-twin in up to 20% of the cases and in ischemic sequelae in about the same proportions in the survivors. Although the symptoms of all these complications are very different, the keystone of their management comes down to either surgical destruction of the inter-twin anastomoses on the chorionic plate when aiming at dual survival or selective and permanent occlusion of the cord of a severely affected twin aiming at protecting the normal co-twin. This can be best achieved by fetoscopic selective laser coagulation and bipolar forceps cord coagulation respectively.

Hematological characteristics in neonates with twin anemia-polycythemia sequence (TAPS)

OBJECTIVE

To evaluate the neonatal hematological features of monochorionic twins with twin anemia-polycythemia sequence (TAPS) and to determine the additional diagnostic value of reticulocyte count measurement.

METHODS

A cohort of consecutive monochorionic twins with TAPS (n = 19) was included in the study and each twin pair was compared with two monochorionic twin pairs (n = 38) unaffected by TAPS or twin-twin transfusion syndrome (TTTS), matched for gestational age at birth. We measured full blood counts on day 1 and determined the incidence of anemia, polycythemia, reticulocytosis and thrombocytopenia.

RESULTS

Median inter-twin hemoglobin (Hb) difference in monochorionic twins with and without TAPS was 13.7 g/dL and 2.4 g/dL, respectively (p < 0.01). Median inter-twin reticulocyte count ratio in twins with and without TAPS was 3.1 and 1.0, respectively (p < 0.01). Thrombocytopenia (platelet count < 150 x 10(9)/L) occurred more often in the TAPS group than in the control group, 45% (17/38) versus 11% (11/38), respectively (p < 0.01). In the TAPS group, mean platelet count was significantly lower in recipients than in donors, 133 x 10(9)/L versus 218 x 10(9)/L, respectively (p < 0.01).

CONCLUSIONS

TAPS twins have a large inter-twin Hb difference in combination with a large inter-twin reticulocyte count ratio. Recipients are more often thrombocytopenic than donors, probably due to polycythemia.

Residual vascular communications in twin-twin transfusion syndrome treated with sequential laser surgery: frequency and clinical implications

OBJECTIVES

The goal of fetoscopic laser surgery for twin-twin transfusion syndrome (TTTS) is to ablate all placental vascular communications, thereby separating the fetal circulatory systems. We sought to ascertain the frequency and clinical implications of residual vascular communications (RVC) post preferential sequential selective laser photocoagulation of communicating vessels (SQLPCV).

STUDY DESIGN

TTTS placentas treated via preferential SQLPCV were examined. Patency of vascular communications was assessed via water and/or milk injections. Cases with intrauterine fetal demise or placental disruption were excluded. Outcomes with and without RVC were compared.

RESULTS

One hundred seventy-four TTTS patients were treated during the study period. Dual survival at birth was 76% (133/174). Of the 133 dual survivors, 105 (79%) submitted an intact placenta. Five of these 105 placentas had RVC (4.8%). Comparison of RVC versus non-RVC cases revealed the following: gestational age at delivery 28.7(6.5) vs. 33.4(3.3) weeks (p=0.178); recipient birth weight 1287(1061) vs. 1973(610) grams (p=0.020); donor birth weight 1429(1369) vs. 1653(715) grams (p=0.518); donor central/eccentric placental cord insertion 80% vs. 17% (p=0.006). One case required a second laser surgery to complete the laser ablation; this placenta did not have RVC after delivery. Otherwise there were no cases of persistent TTTS. One of the 5 RVC cases (20%) exhibited neonatal findings consistent with twin anemia-polycythemia sequence (TAPS), while none of the non-RVC cases had TAPS (p=0.005).

CONCLUSIONS

The rate of RVC was less than 5% among gestations with dual survivors post preferential SQLPCV treatment for TTTS.

Appraisal of the selectivity index in a cohort of patients treated with laser surgery for twin-twin transfusion syndrome

OBJECTIVE

The selectivity index (SI) has been proposed as a measure of technical success in laser surgery for twin-twin transfusion syndrome. Surgeries with an index >-0.25 have been considered highly selective. The purpose of this study was to evaluate the applicability of this index in our patient population.

STUDY DESIGN

The SI was assessed in 314 consecutive laser surgeries and correlated with perinatal survival.

RESULTS

A total of 310 patients (98.7%) underwent a completely selective procedure. The SI was 0.8 in the selective laser photocoagulation of communicating vessels group vs 0.3 in the nonselective laser photocoagulation of communicating vessels group (P = .001). In the selective group perinatal survival of at least 1 twin (92.6% vs 50%) and survival of the donor (75.4% vs 0%) was significantly better (P = .05).

CONCLUSION

The SI as originally proposed is misleading and of limited use as it does not differentiate selective from nonselective procedures. We propose instead using a ratio of selective/nonselective procedures, and selectively coagulated/total number of coagulated vessels to appraise center-specific and patient-specific surgical performance of laser surgery for twin-twin transfusion syndrome.