Patient-specific placental vessel segmentation with limited data.

A major obstacle in applying machine learning for medical fields is the disparity between the data distribution of the training images and the data encountered in clinics. This phenomenon can be explained by inconsistent acquisition techniques and large variations across the patient spectrum. The result is poor translation of the trained models to the clinic, which limits their implementation in medical practice. Patient-specific trained networks could provide a potential solution. Although patient-specific approaches are usually infeasible because of the expenses associated with on-the-fly labeling, the use of generative adversarial networks enables this approach. This study proposes a patient-specific approach based on generative adversarial networks. In the presented training pipeline, the user trains a patient-specific segmentation network with extremely limited data which is supplemented with artificial samples generated by generative adversarial models. This approach is demonstrated in endoscopic video data captured during fetoscopic laser coagulation, a procedure used for treating twin-to-twin transfusion syndrome by ablating the placental blood vessels. Compared to a standard deep learning segmentation approach, the pipeline was able to achieve an intersection over union score of 0.60 using only 20 annotated images compared to 100 images using a standard approach. Furthermore, training with 20 annotated images without the use of the pipeline achieves an intersection over union score of 0.30, which, therefore, corresponds to a 100% increase in performance when incorporating the pipeline. A pipeline using GANs was used to generate artificial data which supplements the real data, this allows patient-specific training of a segmentation network. We show that artificial images generated using GANs significantly improve performance in vessel segmentation and that training patient-specific models can be a viable solution to bring automated vessel segmentation to the clinic.

Autonomous Magnetic Navigation in Endoscopic Image Mosaics.

Endoscopes navigate within the human body to observe anatomical structures with minimal invasiveness. A major shortcoming of their use is their narrow field-of-view during navigation in large, hollow anatomical regions. Mosaics of endoscopic images can provide surgeons with a map of the tool's environment. This would facilitate procedures, improve their efficiency, and potentially generate better patient outcomes. The emergence of magnetically steered endoscopes opens the way to safer procedures and creates an opportunity to provide robotic assistance both in the generation of the mosaic map and in navigation within this map. This paper proposes methods to autonomously navigate magnetic endoscopes to 1) generate endoscopic image mosaics and 2) use these mosaics as user interfaces to navigate throughout the explored area. These are the first strategies, which allow autonomous magnetic navigation in large, hollow organs during minimally invasive surgeries. The feasibility of these methods is demonstrated experimentally both in vitro and ex vivo in the context of the treatment of twin-to-twin transfusion syndrome. This minimally invasive procedure is performed in utero and necessitates coagulating shared vessels of twin fetuses on the placenta. A mosaic of the vasculature in combination with autonomous navigation has the potential to significantly facilitate this challenging surgery.

Fetoscopic laser coagulation for twin-to-twin transfusion syndrome: a comparison of flexible 1.0/1.2 mm fetoscopes with curved sheaths of 2.7/3.3 mm2 vs. 2 mm fetoscopic lens technique with sheaths of 6.6/11.3 mm2.

OBJECTIVES: Fetoscopic laser coagulation of placental anastomoses is usually performed for a treatment of twin-to-twin transfusion syndrome (TTTS). A common complication of fetoscopic laser coagulation for TTTS is preterm preliminary rupture of fetal membranes (PPROM) aggravating the neonatal outcome significantly. However, use of an flexible 1 mm fetoscope with an curved sheath could reduce iatrogenic damage of the amniotic membrane and improve neonatal outcomes after laser treatment. The aim of this study was to compare neonatal outcomes using this flexible fetoscope with curved sheath vs. use of a standard lens technique. METHODS: Outcomes were retrospective analyzed after use of a standard lens fetoscope of 2 mm (sheath 6.63 mm2 or 11.27 mm2 for anterior placenta) and a flexible fetoscope of 1 mm or 1.2 mm (sheath 2.65 mm2 or 3.34 mm2) in two German centers of fetal surgery, performed during 2006-2019. RESULTS: Neonatal outcome of 247 TTTS patients were analyzed including the rates of double and single fetal survival. The survival of at least one fetus was 97.2 % in the group with the ultrathin technique (n=154) compared to 88.3 % (n=93) in the group with the standard lens fetoscope (p=0.008). Survival of both fetuses was not different between groups (81.0 vs. 75.3 %). The procedure to delivery interval was significantly increased using the ultrathin fetoscope (89.1±35.0 d vs. 71.4±35.4 d, p=0.001) resulting in an increased gestational age at delivery by 11 days on average (231.9±28.1 d vs. 221.1±32.7 d, p=0.012). CONCLUSIONS: Fetal survival can be significantly increased following TTTS using flexible fetoscope of 1 mm or 1.2 mm (sheath 2.65 mm2 or 3.34 mm2).

Acute Fetal Metabolomic Changes in Twins Undergoing Fetoscopic Surgery for Twin-Twin Transfusion Syndrome.

Fetuses undergo major surgical stress as well as fluid shifts secondary to both twin-twin transfusion (TTTS) as well as the fetoscopic surgery for treatment of TTTS. While the pathophysiology of TTTS is understood, the acute metabolic changes that fetuses experience from fetoscopic surgery are not. We sought to evaluate the changes in recipient metabolomic profile secondary to TTTS surgery. Amniotic fluid was collected at the beginning and end of four TTTS surgical cases performed from 12/2022-2/2023. Samples were immediately processed and evaluated via NMR-based Metabolomics Facility protocol. In univariate analysis, 12 metabolites (glucose, lactate, and 10 key amino acids) showed statistically significant changes between the beginning and end of the surgery. Among these, 11 metabolites decreased at the end, while only lactate increased. Supervised oPLS-DA modeling revealed pyruvate and lactate as the two metabolites most impact on the variance between cases, and that 40% of metabolomic changes could be attributed directly to the timing that the sample was taken (i.e., if pre- or postoperatively). These results indicate significant metabolic changes in the recipient twin during fetoscopic surgery for TTTS. These findings of decreased glucose, increased lactate, and decreased amnio acids would indicate increased catabolism during surgery. This study raises questions regarding optimal maternal and fetal nutrition during surgery and if nutritional status could be optimized to further improve twin survival during fetoscopic surgery.

Perinatal outcomes following fetoscopic laser surgery for early twin-to-twin transfusion syndrome: Systematic review and meta-analysis.

INTRODUCTION: Our objective was to investigate outcomes in twin-to-twin transfusion syndrome (TTTS) treated with fetoscopic laser surgery (FLS) at <18 weeks vs ≥18 weeks, and to conduct subgroup analysis of TTTS with FLS at <16 weeks vs 16-18 weeks. MATERIAL AND METHODS: PubMed, Scopus and Web of Science were searched systematically from inception until May 2023. Primary outcome was survival, and secondary outcomes included preterm premature rupture of membranes (PPROM), preterm birth and gestational age (GA) at delivery. RESULTS: Nine studies encompassing 1691 TTTS pregnancies were included. TTTS stage III was significantly more common in TTTS pregnancies treated with FLS at <18 weeks (odds ratio [OR] 2.84, 95% confidence interval [CI] 1.24-6.54), and procedure duration was shorter at <18 weeks (MD -5.27 minutes, 95% CI -9.19 to -1.34). GA at delivery was significantly earlier in TTTS pregnancies treated with FLS at <18 weeks (MD -3.12 weeks, 95% CI -6.11 to -0.13). There were no significant differences in outcomes, including PPROM, PPROM at <7 days post-FLS, preterm birth at <28 and <32 weeks, delivery at <7 days post-FLS, and survival outcomes, including fetal demise, live birth and neonatal survival. Similarly, TTTS stage III was more common in TTTS with FLS at <16 weeks than at 16-18 weeks (OR 2.95, 95% CI 1.62-5.35), with no significant differences in the aforementioned outcomes. CONCLUSIONS: In early TTTS treated with FLS, outcomes were comparable between those treated at <18 weeks compared with ≥18 weeks except for GA at delivery, which was 3 weeks earlier. In the subset treated at <16 weeks vs 16-18 weeks, the procedure was feasible without an increased risk of very early preterm birth or perinatal mortality.

Neonatal hemodynamics of recipient twins after fetoscopic selective laser coagulation for twin-to-twin transfusion syndrome: An unicist classification.

To characterize the neonatal hemodynamic profiles in recipients born after twin-to-twin transfusion syndrome (TTTS) treated with fetoscopic selective laser coagulation (FSLC). Retrospective analysis during the first month of life of recipient twins. Of the 480 newborns born during an 11-year period, 138 recipient twins with prenatal FSLC were classified into four groups: no hemodynamic impairment (NoHI, n = 102, 74%), isolated high blood pressure (HighBP, n = 18, 13%), right ventricular outflow tract obstruction (RVOTO, n = 10, 7%), and cardiac failure (CF, n = 8, 6%). The time (median (IQR)) between FSLC and birth was significantly shorter in the HighBP (36 days (23-54)) and CF (44 days (18-54)) groups than in the RVOTO (91 days (68-112)) and NoHi (82 days (62-104)) groups (p < 0.001).     Conclusion: Four distinct and well-characterized groups of recipients were identified based on their hemodynamics. High blood pressure and heart failure occurred in approximately 20% of the infants and were associated with a time between laser coagulation and birth of less than 2 months. What is Known: • Twin-to-twin transfusion syndrome (TTTS) is characterized by a hemodynamic imbalance that leads to high fetal and neonatal mortality if left untreated. One-third of recipient twins born without prenatal fetoscopic laser coagulation (FSLC) develop a life-threatening cardiac failure. What is New: • Four distinct groups of recipient twins with prenatal FSLC have been identified based on their hemodynamics. High blood pressure and cardiac failure occurred in 20% of the infants and were associated with an interval between FSLC and birth of less than 2 months.

A systematic review of early intrauterine intervention at 12 + 0 to 16 + 6 weeks in twin reversed arterial perfusion sequence.

There is some evidence that in twin reversed arterial perfusion sequence, intervention at early gestational age could prevent a spontaneous death of the pump twin, achieving a better global survival. OBJECTIVE: To review the perinatal outcomes of early intervention in pregnancies complicated by twin reversed arterial perfusion (TRAP) sequence. STUDY DESIGN: A comprehensive search from inception to December 2022 was conducted on databases including MEDLINE, EMBASE, Cochrane Library and LILACS. All studies that reported intervention in twin or triplet pregnancy complicated with TRAP sequence at 12 + 0 to 16 + 6 weeks of gestation were eligible. A descriptive and bivariate analysis was performed. RESULTS: Out of the 222 full-text articles, 44 studies reporting 108 cases of early intervention in TRAP sequence were included. A successful procedure was achieved in 105 (95.5 %) interventions: 89 (94.7 %) among twin pregnancies and 16(100 %) among triplet pregnancies. An overall livebirth rate was achieved in 75 patients (70.8 %): intrafetal laser group 55 (73.3 %), radiofrequency 10 (76.9 %) and endoscopic laser 3 (75.0 %). The median gestational age at delivery was 38 + 0 (37 + 4 - 39 + 4) weeks. The median treatment-delivery interval was 23 + 2 (IQR, 21 + 0-25 + 6) weeks. The most frequent adverse outcomes reported were preterm labor in 7 (13.7 %) patients. There were no severe adverse maternal outcomes. CONCLUSION: Early intervention with intrafetal laser and radiofrequency in TRAP sequence achieves a livebirth rate of the pump twin of about 75 %.

Predictors of fetal death, neonatal survival and neurological outcomes in severe twin-twin transfusion syndrome treated by laser ablation of placental vessels.

OBJECTIVES: To identify predictors of outcomes in severe twin oligo-polyhydramnios sequence (TOPS) with or without twin anemia-polycythemia sequence (TAPS) and/or selective fetal growth restriction (SFGR) treated by laser ablation of placental vessels (LAPV). METHODS: Analysis of cases treated from 2011 to 2022. Variables evaluated Prenatal predictors: stages of TOPS, presence of TAPS and/or SFGR; pre-LAPV fetal ultrasound parameters; peri-LAPV variables. Perinatal predictors: GA at birth; birthweight; Apgar scores; transfontanellar ultrasonography (TFUS). OUTCOME VARIABLES: fetal death, neonatal survival, infant's neurodevelopment. Binary logistic regression analyses were performed to detect predictors of outcomes. RESULTS: 265 cases were included. Predictors of post-LAPV donor fetus' death were delta EFW (p:0.045) and absent/reverse end-diastolic flow in the umbilical artery (AREDF-UA) (p < 0.001). The predictor of post-LAPV recipient fetus' death was hydrops (p:0.009). Predictors of neonatal survival were GA at birth and Apgar scores. Predictors of infant's neurodevelopment were TFUS and pre-LAPV middle cerebral artery Doppler (MCAD) for the donor twin; and pre-LAPV ductus venosus' flow and MCAD for the recipient twin. CONCLUSIONS: Prediction of fetal death, neonatal survival and infant's neurodevelopment is possible in cases of TOPS associated or not with SFGR and/or TAPS that were treated by LAPV.

Management of short cervix in twin-to-twin transfusion syndrome: a role for pessary placement following fetoscopic laser surgery?

BACKGROUND: Preterm labor and delivery is a major concern for patients with twin-to-twin transfusion syndrome undergoing fetoscopic laser surgery. A preoperative short cervix is a risk factor for preterm labor. Pessary placement is a short-acting intervention that may be useful to reduce this adverse event. OBJECTIVE: This study aimed to investigate the relationship between pessary placement and preterm delivery in monochorionic twin pregnancies with twin-to-twin transfusion syndrome and a short cervix before fetoscopic laser surgery. STUDY DESIGN: This was a retrospective study in 2 centers, including all pregnancies affected by twin-to-twin transfusion syndrome that underwent fetoscopic laser surgery with the Solomon technique between 2013 and 2022 (center A) and 2014 and 2022 (center B) with a preoperative cervical length below 25 mm. This study explored the correlation between cervical length and fetoscopic laser surgery-to-delivery interval following active or expectant management and compared perinatal outcomes between patients managed expectantly and patients managed with pessary placement, using multivariate analysis to control for potential confounders. Patients with a cervical length below 5 mm were not included in the comparative analysis. RESULTS: Of 685 patients, 134 met the inclusion criteria. Moreover, 21 patients were treated with a cervical cerclage and excluded from the analysis, leaving 113 patients for the final analysis. There was a significant negative correlation between cervical length at fetoscopic laser surgery and the risk of early delivery (adjusted odds ratio, 0.66; 95% confidence interval, 0.49-0.81; P<.001). The use of a pessary correlated with fewer patients delivering before 28 weeks of gestation (adjusted odds ratio, 0.28; 95% confidence interval, 0.09-0.75), fewer double neonatal demise (adjusted odds ratio, 0.2; 95% confidence interval, 0.05-0.75). Posthoc subgroup analysis suggested that these improvements were essentially noticeable for cervical lengths between 5 and 18 mm, where pessary placement was associated with an increased fetoscopic laser surgery-to-delivery interval (+24 days; 95% confidence interval, 0.86-42; P=.042) and later gestational age at delivery (+3.3 weeks; 95% confidence interval, 0.86-42; P=.035). CONCLUSION: Patients with a moderately shortened cervix, between 5 and 18 mm, may benefit from pessary placement after fetoscopic surgery for twin-to-twin transfusion syndrome, resulting in a reduction of adverse neonatal outcomes, double neonatal demise, and severe preterm delivery.

Consensus protocol for management of early and late twin-twin transfusion syndrome: Delphi study.

OBJECTIVE: Fetoscopic laser photocoagulation (FLP) is a well-established treatment for twin-twin transfusion syndrome (TTTS) between 16 and 26 weeks' gestation. High-quality evidence and guidelines regarding the optimal clinical management of very early (prior to 16 weeks), early (between 16 and 18 weeks) and late (after 26 weeks) TTTS are lacking. The aim of this study was to construct a structured expert-based clinical consensus for the management of early and late TTTS. METHODS: A Delphi procedure was conducted among an international panel of experts. Participants were chosen based on their clinical expertise, affiliation and relevant publications. A four-round Delphi survey was conducted using an online platform and responses were collected anonymously. In the first round, a core group of experts was asked to answer open-ended questions regarding the indications, timing and modes of treatment for early and late TTTS. In the second and third rounds, participants were asked to grade each statement on a Likert scale (1, completely disagree; 5, completely agree) and to add any suggestions or modifications. At the end of each round, the median score for each statement was calculated. Statements with a median grade of 5 without suggestions for change were accepted as the consensus. Statements with a median grade of 3 or less were excluded from the Delphi process. Statements with a median grade of 4 were modified according to suggestions and reconsidered in the next round. In the last round, participants were asked to agree or disagree with the statements, and those with more than 70% agreement without suggestions for change were considered the consensus. RESULTS: A total of 122 experts met the inclusion criteria and were invited to participate, of whom 53 (43.4%) agreed to take part in the study. Of those, 75.5% completed all four rounds. A consensus on the optimal management of early and late TTTS was obtained. FLP can be offered as early as 15 weeks' gestation for selected cases, and can be considered up to 28 weeks. Between 16 and 18 weeks, management should be tailored according to Doppler findings. CONCLUSIONS: A consensus-based treatment protocol for early and late TTTS was agreed upon by a panel of experts. This protocol should be modified at the discretion of the operator, according to their experience and the specific demands of each case. This should advance the quality of future studies, guide clinical practice and improve patient care. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

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.

Prenatal Risk Factors and Outcomes of Pseudoamniotic Band Sequence following Fetoscopic Laser Surgery: Systematic Review, and Meta-Analysis.

BACKGROUND: Pseudoamniotic band sequence (PABS) is a rare iatrogenic consequence of invasive fetal interventions, most commonly fetoscopic laser surgery (FLS) in monochorionic multiple pregnancies complicated by twin-to-twin transfusion syndrome (TTTS). OBJECTIVES: The aim of this study was to investigate prenatal risk factors and perinatal outcomes for pregnancies involving PABS after FLS for TTTS and compare outcomes between those undergoing fetoscopic band release versus not. METHOD: We conducted a systematic search of PubMed, Scopus, and Web of Science on studies reporting PABS following FLS for TTTS. A meta-analysis of pooled proportions was conducted. RESULTS: There were 16 studies covering 47 pregnancies complicated by PABS following FLS, mostly case series and case reports. The incidence of PABS was 2%, with the recipient twin affected in 94% of the cases. Pregnancies complicated by PABS were associated with inter-twin septostomy in 32% and chorioamniotic separation (CAS) in 90%. The mean gestational age (GA) at FLS and delivery were 17.7 and 30.9 weeks, respectively. Preterm premature rupture of membranes (PPROM) happened in 62% of pregnancies. The risk of preterm birth (PTB) <34 weeks, <32 weeks, and <28 weeks were 94%, 67%, and 31%, respectively. There were 41% fetal demises and 64% live births among the affected fetuses. Results of fetoscopic band release versus not were comparable, including GA at delivery, PPROM, and PTB at 32 weeks. It was noted that the likelihood of PTB by 28 weeks (67% vs. 23%) and fetal death (50% vs. 39%) were higher in the band release group. It was similar between groups in terms of postnatal amputation. CONCLUSIONS: PABS causes amputations or fetal death in more than one-third of cases. Pregnancies with an inter-twin septostomy, CAS, advanced TTTS staging, and early GA are more likely to experience PABS. In addition, more than a third of FLS-treated TTTS resulted in PTB and PPROM. PABS cases with prenatal band release showed higher rates of PTB and fetal death, but the data were from small, heterogeneous studies.

Hepatic arterial buffer response: activation in donor fetuses and the effect of laser ablation of intertwin anastomosis.

OBJECTIVES: Hepatic arterial buffer response (HABR) is an important defence mechanism for maintaining liver blood flow. It is suspected that HABR is active in monochorionic diamniotic twins (MCDA) with twin-to-twin transfusion syndrome (TTTS) where donor compensates a setting of volume depletion and the recipient an overload. The present study investigates whether in TTTS, HABR is active in donor and/or recipient individually and try to determine if the activation of HABR is a direct response to TTTS. METHODS: Hepatic artery (HA) peak systolic velocity (PSV) was measured in normal MCDA fetuses and TTTS. Correlation with relevant fetal Dopplers and characteristics were determined. Z-scores for HA-PSV (HAV-Z) were calculated and its association with TTTS in donors and recipients were determined as well as changes in HAV-Z after laser treatment. RESULTS: In this study 118 MCDA were included, 61.9 % normal and 38.1 % TTTS. Of the TTTS 22 required laser treatment. A total of 382 scans were performed in normal group and 155 in TTTS. Our data demonstrates that in donors HAV-Z was 2.4 Z-scores higher compared to normal fetuses (ß=2.429 95 % CI 1.887, 2.971; p<0.001) and after laser treatment HAV-Z reduced (ß=-1.829 95 % CI -2.593, -1.064; p<0.001). There was no significant difference between recipients and normal (ß=-0.092 95 % CI -0.633, 0.449; p=0.738). CONCLUSIONS: HABR is active in TTTS, promoting an increased hepatic blood flow in donors. The activation is direct response to TTTS as shown by the reduction in HAV-Z after laser. This finding provides important insights into the pathophysiology of TTTS.

Laser fetoscopy ablation for twin-twin transfusion syndrome may reduce the risk of ROP.

PURPOSE: Twin-twin transfusion syndrome (TTTS) is a condition wherein monochorionic twins share a common placenta with placental anastomoses between the two foetal circulations. Most infants who survive TTTS are born prematurely. This study aimed to determine whether fetoscopic laser ablation (FLA) can reduce the risk of retinopathy of prematurity (ROP) and whether TTTS was a risk factor for ROP. METHODS: This single-centre, retrospective, comparative study included 32 monochorionic twins with TTTS matched for gestational age, birthweight and sex to premature twins and singletons without TTTS (n = 68; twins, n = 34; and singletons, n = 34) born between 2003 and 2022. A single ophthalmologist recorded the fundus findings. FLA was performed using Solomon's technique to separate the vascular systems of the twins with TTTS. RESULTS: The gestational age and weight of premature infants with TTTS treated with FLA were significantly higher than those of untreated infants (p = 0.001 and p = 0.001, respectively); however, the hyaline membrane grade was lower (p = 0.004). A significant increase in weight (g/day) (p = 0.002) and lesser avascular area in the peripheral temporal retina (p = 0.045) was observed at postnatal week 4. The risk of ROP in the FLA group was 2.6 times (13.3% vs. 35.3%) lower than that in the non-FLA group; however, this difference was not significant. The incidence of any stage of ROP (25% vs. 18%) and treatment for ROP type 1 (6.25% vs. 5.9%) did not differ significantly between monochorionic twins with TTTS and premature infants without TTTS. CONCLUSION: The gestational age of premature infants with TTTS treated with FLA was higher than that of untreated infants. Moreover, a reduction in complications of prematurity was also observed. Laser fetoscopy in twin-twin transfusion syndrome may reduce the risk of ROP, but the difference was not statistically significant in this small study.

Maternal hemodynamic evaluation in monochorionic twin pregnancy complicated by twin-to-twin transfusion syndrome treated with fetoscopic laser surgery.

BACKGROUND: Maternal cardiovascular adaptations are amplified in twin pregnancies to support the metabolic request of the feto-placental unit. Few studies have evaluated the maternal hemodynamics changes after routine use of laser surgery in the treatment of twin-twin transfusion syndrome. OBJECTIVE: The aim of our study was to evaluate hemodynamic changes in monochorionic twin pregnancies complicated by twin-twin transfusion syndrome before and after treatment with fetoscopic laser surgery. STUDY DESIGN: A prospective observational study from 2020 to 2022, included monochorionic twin pregnancies complicated with twin-twin transfusion syndrome undergoing laser surgery between 16 and 26 weeks of gestation. To assess placental function and perfusion, uterine artery pulsatility index, hemoglobin, hematocrit, and soluble fms-like tyrosine kinase-1/placental growth factor ratio sampling prelaser and 24 hours postlaser were measured. Echocardiography by a single cardiologist evaluated maternal hemodynamics at presurgery, 24 hours, and 1 week postlaser. Those data were crosswise compared with cardiovascular indices of uncomplicated monochorionic pregnancies recruited at the same gestational age using nonparametric tests. Moreover, we fitted random-intercept linear regression models to investigate maternal hemodynamic changes according to the amount of amniotic fluid drained during laser surgery. RESULTS: Forty-two twin-twin transfusion syndrome pregnancies with a median gestational age of 19.1 (17.4-20.9) weeks and 15 uncomplicated monochorionic pregnancies at the same gestational age were enrolled. Overall survival rate after laser was 72% with delivery at a median gestational age of 31.5 (27-34) weeks. Significant changes in blood chemistry and placental function were observed in the twin-twin transfusion syndrome group, along with alterations in arterial pressure, heart rate, cardiac output, and ventricular strain, eventually aligning with the uncomplicated group's values by 1 week postlaser. The amount of amniodrainage, with a 1000 ml cut-off, did not significantly impact hemodynamic parameters. Lastly, we detected a percentage of laser surgery complications in agreement with international literature and we did not record any maternal procedure-related problems. CONCLUSION: Our analysis highlighted that maternal cardiovascular status in monochorionic twin pregnancy complicated by twin-twin transfusion syndrome was more dynamic and; 1 week after fetoscopic laser ablation of placental anastomosis completed by amniodrainage, maternal hemodynamic parameters restored to values similar to uncomplicated monochorionic twin pregnancies.

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.

Monochorionic Twins: TTTS, TAPS, and Selective Fetal Growth Restriction.

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 monochorionic twins leads to unique complications, including twin-to-twin transfusion syndrome, the twin anemia-polycythemia sequence, and selective fetal growth restriction. Not only does the understanding of the monochorionic placenta lead to an understanding of the pathophysiology of the complications of monochorionic twins, but it also has led to the development of highly effective directed fetal therapy via fetoscopic laser coagulation used in twin-to-twin transfusion syndrome.

Feasibility of continuous intra-uterine pressure measurements during amnioreduction in twin-to-twin transfusion syndrome therapy.

INTRODUCTION: This work explores the feasibility of simultaneous and continuous intra-abdominal, intra-uterine, and arterial blood pressure measurements to examine the hemodynamic perturbation expected during therapeutic amnioreduction and to better understand the protective role of the placenta during that treatment. METHODS: Patients with twin-to-twin transfusion syndrome were treated with fetoscopic laser ablation followed by amnioreduction. Intra-abdominal, intra-uterine, and mean arterial pressures were simultaneously recorded during amnioreduction performed in steps of 200 mL. Placental thickness and uterine dimensions were measured before and after amnioreduction by ultrasonography. RESULTS: Useful pressure recordings were obtained between volume reduction steps and short hands-off periods in four studies. Median amnioreduction volume was 1400 mL corresponding to a median uterine volume reduction of 1121 mL. Mean intra-uterine pressure significantly fell from 24.8 to 13.6 mmHg (p = 0.011) and intra-abdominal pressure significantly decreased from 13.4 to 9.2 mmHg after amnioreduction (p = 0.015). Uterine pressure recordings revealed transient contractions (A, in mmHg) following individual amnioreduction steps, which increased with fractional amnioreduction (F, no dimension) (A = 17.23*F + 11.81; r = 0.50, p = 0.001). DISCUSSION: Simultaneous and continuous measurement of intra-abdominal, intra-uterine, and arterial blood pressures during amnioreduction is feasible. The dynamics reveal transient uterine contractions reaching levels comparable to those seen during childbirth which seem to oppose impending maternal hypovolemia by placental steal at the expense of temporarily reducing placental perfusion pressure and underline the importance of uterine and placental interaction.