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.

Use of super resolution reconstruction MRI for surgical planning in Placenta accreta spectrum disorder: Case series.

INTRODUCTION: Comprehensive imaging using ultrasound and MRI of placenta accreta spectrum (PAS) aims to prevent catastrophic haemorrhage and maternal death. Standard MRI of the placenta is limited by between-slice motion which can be mitigated by super-resolution reconstruction (SRR) MRI. We applied SRR in suspected PAS cases to determine its ability to enhance anatomical placental assessment and predict adverse maternal outcome. METHODS: Suspected PAS patients (n = 22) underwent MRI at a gestational age (weeks + days) of (32+3±3+2, range (27+1-38+6)). SRR of the placental-myometrial-bladder interface involving rigid motion correction of acquired MRI slices combined with robust outlier detection to reconstruct an isotropic high-resolution volume, was achieved in twelve. 2D MRI or SRR images alone, and paired data were assessed by four radiologists in three review rounds. All radiologists were blinded to results of the ultrasound, original MR image reports, case outcomes, and PAS diagnosis. A Random Forest Classification model was used to highlight the most predictive pathological MRI markers for major obstetric haemorrhage (MOH), bladder adherence (BA), and placental attachment depth (PAD). RESULTS: At delivery, four patients had placenta praevia with no abnormal attachment, two were clinically diagnosed with PAS, and six had histopathological PAS confirmation. Pathological MRI markers (T2-dark intraplacental bands, and loss of retroplacental T2-hypointense line) predicting MOH were more visible using SRR imaging (accuracy 0.73), in comparison to 2D MRI or paired imaging. Bladder wall interruption, predicting BA, was only easily detected by paired imaging (accuracy 0.72). Better detection of certain pathological markers predicting PAD was found using 2D MRI (placental bulge and myometrial thinning (accuracy 0.81)), and SRR (loss of retroplacental T2-hypointense line (accuracy 0.82)). DISCUSSION: The addition of SRR to 2D MRI potentially improved anatomical assessment of certain pathological MRI markers of abnormal placentation that predict maternal morbidity which may benefit surgical planning.

A systematic review of brachial plexus injuries after caesarean birth: challenging delivery?

BACKGROUND: Caesarean section (CS) is widely perceived as protective against obstetric brachial plexus injury (BPI), but few studies acknowledge the factors associated with such injury. The objectives of this study were therefore to aggregate cases of BPI after CS, and to illuminate risk factors for BPI. METHODS: Pubmed Central, EMBASE and MEDLINE databases were searched using free text: ("brachial plexus injury" or "brachial plexus injuries" or "brachial plexus palsy" or "brachial plexus palsies" or "Erb's palsy" or "Erb's palsies" or "brachial plexus birth injury" or "brachial plexus birth palsy") and ("caesarean" or "cesarean" or "Zavanelli" or "cesarian" or "caesarian" or "shoulder dystocia"). Studies with clinical details of BPI after CS were included. Studies were assessed using the National Institutes for Healthy Study Quality Assessment Tool for Case Series, Cohort and Case-Control Studies. MAIN RESULTS: 39 studies were eligible. 299 infants sustained BPI after CS. 53% of cases with BPI after CS had risk factors for likely challenging handling/manipulation of the fetus prior to delivery, in the presence of considerable maternal or fetal concerns, and/or in the presence of poor access due to obesity or adhesions. CONCLUSIONS: In the presence of factors that would predispose to a challenging delivery, it is difficult to justify that BPI could occur due to in-utero, antepartum events alone. Surgeons should exercise care when operating on women with these risk factors.

The impact of ultrasound-based antenatal screening strategies to detect vasa praevia in the United Kingdom: An exploratory study using decision analytic modelling methods.

The objective of this exploratory modelling study was to estimate the effects of second-trimester, ultrasound-based antenatal detection strategies for vasa praevia (VP) in a hypothetical cohort of pregnant women. For this, a decision-analytic tree model was developed covering four discrete detection pathways/strategies: no screening; screening targeted at women undergoing in-vitro fertilisation (IVF); screening targeted at women with low-lying placentas (LLP); screening targeted at women with velamentous cord insertion (VCI) or a bilobed or succenturiate (BL/S) placenta. Main outcome measures were the number of referrals to transvaginal sonography (TVS), diagnosed and undiagnosed cases of VP, overdetected cases of VCI, and VP-associated perinatal mortality. The greatest number of referrals to TVS occurred in the LLP-based (2,083) and VCI-based screening (1,319) pathways. These two pathways also led to the highest proportions of pregnancies diagnosed with VP (VCI-based screening: 552 [78.9% of all pregnancies]; LLP-based: 371 [53.5%]) and the lowest proportions of VP leading to perinatal death (VCI-based screening: 100 [14.2%]; LLP-based: 196 [28.0%]). In contrast, the IVF-based pathway resulted in 66 TVS referrals, 50 VP diagnoses (7.1% of all VP pregnancies), and 368 (52.6%) VP-associated perinatal deaths which was comparable to the no screening pathway (380 [54.3%]). The VCI-based pathway resulted in the greatest detection of VCI (14,238 [99.1%]), followed by the IVF-based pathway (443 [3.1%]); no VCI detection occurred in the LLP-based or no screening pathways. In conclusion, the model results suggest that a targeted LLP-based approach could detect a substantial proportion of VP cases, while avoiding VCI overdetection and requiring minimal changes to current clinical practice. High-quality data is required to explore the clinical and cost-effectiveness of this and other detection strategies further. This is necessary to provide a robust basis for future discussion about routine screening for VP.

Magnetic resonance imaging in late pregnancy to improve labour and delivery outcomes - a systematic literature review.

BACKGROUND: Magnetic resonance imaging (MRI) provides excellent soft tissue visualisation which may be useful in late pregnancy to predict labour outcome and maternal/neonatal birth trauma. OBJECTIVE: To study if MRI in late pregnancy can predict maternal and neonatal outcomes of labour and birth. METHODS: Systematic review of studies that performed MRI in late pregnancy or immediately postpartum. Studies were included if they imaged maternal pelvic or neonatal structures and assessed birth outcome. Meta-analysis was not performed due to the heterogeneity of studies. RESULTS: Eighteen studies were selected. Twelve studies explored the value of MRI pelvimetry measurement and its utility to predict cephalopelvic disproportion (CPD) and vaginal breech birth. Four explored cervical imaging in predicting time interval to birth. Two imaged women in active labour and assessed mouldability of the fetal skull. No marker of CPD had both high sensitivity and specificity for predicting labour outcome. The fetal pelvic index yielded sensitivities between 59 and 60%, and specificities between 34 to 64%. Similarly, although the sensitivity of the cephalopelvic disproportion index in predicting labour outcome was high (85%), specificity was only 56%. In women with breech presentation, MRI was demonstrated to reduce the rates of emergency caesarean section from 35 to 19%, and allowed better selection of vaginal breech birth. Live birth studies showed that the fetal head undergoes a substantial degree of moulding and deformation during cephalic vaginal birth, which is not considered during pelvimetry. There are conflicting studies on the role of MRI in cervical imaging and predicting time interval to birth. CONCLUSION: MRI is a promising imaging modality to assess aspects of CPD, yet no current marker of CPD accurately predicts labour outcome. With advances in MRI, it is hoped that novel methods can be developed to better identify individuals at risk of obstructed or pathological labour. Its role in exploring fetal head moulding as a marker of CPD should be further explored.

Foetal loss after chorionic villus sampling and amniocentesis in twin pregnancies: A multicentre retrospective cohort study.

OBJECTIVE: We aimed to determine foetal losses for DCDA and MCDA twins following transabdominal CVS or amniocentesis performed <22+0  weeks. METHODS: Retrospective cohort study conducted in the UK and Belgium 01/01/00-01/06/20. Cases with unknown chorionicity, monochorionic complications or complex procedures were excluded. Uncomplicated DCDA and MCDA twins without invasive procedures were identified as controls. We reported foetal losses <24+0  weeks and losses of genetically and structurally normal foetuses. RESULTS: Outcomes were compared for DCDA foetuses; 258 after CVS with 3406 controls, 406 after amniocentesis with 3390 controls plus MCDA foetuses, 98 after CVS with 1124 controls, and 160 after amniocentesis with 1122 controls. There were more losses <24+0  weeks with both procedures in DCDA (CVS RR 5.54 95% CI 3.38-9.08, amniocentesis RR 2.36 95% CI 1.22-4.56) and MCDA twins (CVS RR 5.14 95% CI 2.51-10.54, amniocentesis RR 7.01 95% CI 3.86-12.74). Losses of normal foetuses were comparable to controls (DCDA CVS RR 0.39 95% CI 0.05-2.83, DCDA amniocentesis RR 1.16 95% CI 0.42-3.22, MCDA CVS RR 2.3 95% CI 0.71-7.56, and MCDA amniocentesis RR 1.93 95% CI 0.59-6.38). CONCLUSIONS: This study indicates increased foetal losses for DCDA and MCDA twins following CVS and amniocentesis with uncertain risk to normal foetuses.

A push for evidence: An effective training in operative birth.

Effective training in operative birth should be the only type of operative birth that trains the junior obstetricians who are exposed to it. Although it remains difficult to fully characterise, effective training in operative birth is likely to include (i) realistic, local, integrated simulation training and (ii) hands-on senior support for an extended period of time. To further improve skills training in operative birth, an evaluation of the real-world effectiveness of current training should take place, a core outcome set for clinical trials should be developed, and real-time reporting and tracking of practitioner-specific outcome measures should be implemented.

Ursodeoxycholic acid in intrahepatic cholestasis of pregnancy: a systematic review and individual participant data meta-analysis.

BACKGROUND: Ursodeoxycholic acid is commonly used to treat intrahepatic cholestasis of pregnancy, yet its largest trial detected minimal benefit for a composite outcome (stillbirth, preterm birth, and neonatal unit admission). We aimed to examine whether ursodeoxycholic acid affects specific adverse perinatal outcomes. METHODS: In this systematic review and individual participant data meta-analysis, we searched PubMed, Web of Science, Embase, MEDLINE, CINAHL, Global Health, MIDIRS, and Cochrane without language restrictions for relevant articles published between database inception, and Jan 1, 2020, using search terms referencing intrahepatic cholestasis of pregnancy, ursodeoxycholic acid, and perinatal outcomes. Eligible studies had 30 or more study participants and reported on at least one individual with intrahepatic cholestasis of pregnancy and bile acid concentrations of 40 µmol/L or more. We also included two unpublished cohort studies. Individual participant data were collected from the authors of selected studies. The primary outcome was the prevalence of stillbirth, for which we anticipated there would be insufficient data to achieve statistical power. Therefore, we included a composite of stillbirth and preterm birth as a main secondary outcome. A mixed-effects meta-analysis was done using multi-level modelling and adjusting for bile acid concentration, parity, and multifetal pregnancy. Individual participant data analyses were done for all studies and in different subgroups, which were produced by limiting analyses to randomised controlled trials only, singleton pregnancies only, or two-arm studies only. This study is registered with PROSPERO, CRD42019131495. FINDINGS: The authors of the 85 studies fulfilling our inclusion criteria were contacted. Individual participant data from 6974 women in 34 studies were included in the meta-analysis, of whom 4726 (67·8%) took ursodeoxycholic acid. Stillbirth occurred in 35 (0·7%) of 5097 fetuses among women with intrahepatic cholestasis of pregnancy treated with ursodeoxycholic acid and in 12 (0·6%) of 2038 fetuses among women with intrahepatic cholestasis of pregnancy not treated with ursodeoxycholic acid (adjusted odds ratio [aOR] 1·04, 95% CI 0·35-3·07; p=0·95). Ursodeoxycholic acid treatment also had no effect on the prevalence of stillbirth when considering only randomised controlled trials (aOR 0·29, 95% CI 0·04-2·42; p=0·25). Ursodeoxycholic acid treatment had no effect on the prevalence of the composite outcome in all studies (aOR 1·28, 95% CI 0·86-1·91; p=0·22), but was associated with a reduced composite outcome when considering only randomised controlled trials (0·60, 0·39-0·91; p=0·016). INTERPRETATION: Ursodeoxycholic acid treatment had no significant effect on the prevalence of stillbirth in women with intrahepatic cholestasis of pregnancy, but our analysis was probably limited by the low overall event rate. However, when considering only randomised controlled trials, ursodeoxycholic acid was associated with a reduction in stillbirth in combination with preterm birth, providing evidence for the clinical benefit of antenatal ursodeoxycholic acid treatment. FUNDING: Tommy's, the Wellcome Trust, ICP Support, and the National Institute for Health Research.

Monochorionic twins discordant for trisomy 13: A case report, systematic literature search and synthesis of available evidence.

This article presents the tenth reported case of monochorionic twins discordant for trisomy 13. Discordant aneuploidies in monochorionic twins are rare. Aetiologies include mitotic error in early cell division and "rescue" chromosome loss in an initially trisomic zygote. Clinicians should offer early amniocentesis of both sacs and consider selective termination.

Velamentous cord insertion: results from a rapid review of incidence, risk factors, adverse outcomes and screening.

BACKGROUND: Velamentous cord insertion (VCI) is an umbilical cord attachment to the membranes surrounding the placenta instead of the central mass. VCI is strongly associated with vasa praevia (VP), where umbilical vessels lie in close proximity to the internal cervical os. VP leaves the vessels vulnerable to rupture, which can lead to fatal fetal exsanguination. Screening for VP using second-trimester transabdominal sonography (TAS) to detect VCI has been proposed. We conducted a rapid review investigating the quality, quantity and direction of evidence available on the epidemiology, screening test accuracy and post-screening management pathways for VCI. METHODS: MEDLINE, Embase and the Cochrane Library were searched on 5 July 2016 and again on 11 October 2019, using general search terms for VP and VCI. Only peer-reviewed articles reporting on the epidemiology of VCI, the accuracy of the screening test and/or downstream management pathways for VCI pregnancies were included. Quality and risk of bias of each included study were assessed using pre-specified tools. RESULTS: Forty-one relevant publications were identified; all but one were based on non-UK pregnancy cohorts, and most included relatively few VCI cases. The estimated incidence of VCI was 0.4-11% in singleton pregnancies, with higher incidence in twin pregnancies (1.6-40%). VCI incidence was also increased among pregnancies with one or more other risk factors, including in vitro fertilisation pregnancies or nulliparity. VCI incidence among women without any known risk factors was unclear. VCI was associated with adverse perinatal outcomes, most notably pre-term birth and emergency caesarean section in singleton pregnancies, and perinatal mortality in twins; however, associations varied across studies and the increased risk was typically low or moderate compared with pregnancies without VCI. In studies on limited numbers of cases, screening for VCI using TAS had good overall accuracy, driven by high specificity. No studies on post-screening management of VCI were identified. CONCLUSIONS: Literature on VCI epidemiology and outcomes is limited and low-quality. The accuracy of second-trimester TAS and the benefits and harms of screening cannot be determined without prospective studies in large cohorts. Modelling studies may indicate the feasibility and value of studying the epidemiology of VCI and the potential impact of detecting VCI as part of a population screening programme for VP.

Fetal surgery for open spina bifida.

KEY CONTENT: Spina bifida is a congenital neurological condition with lifelong physical and mental effects.Open fetal repair of the spinal lesion has been shown to improve hindbrain herniation, ventriculoperitoneal shunting, independent mobility and bladder outcomes for the child and, despite an increased risk of prematurity, does not seem to increase the risk of neurodevelopmental impairment.Open fetal surgery is associated with maternal morbidity.Surgery at our institution is offered and performed according to internationally agreed criteria and protocols.Further evidence regarding long-term outcomes, fetoscopic repair and alternative techniques is awaited. LEARNING OBJECTIVES: To understand the clinical effects, potential prevention and prenatal diagnosis of spina bifida.To understand the rationale and evidence supporting the benefits and risks of fetal repair of open spina bifida.To understand the criteria defining those who are likely to benefit from fetal surgery. ETHICAL ISSUES: The concept of the fetus as a patient, and issues surrounding fetal death or the need for resuscitation during fetal surgery.The associated maternal morbidity in a procedure performed solely for the benefit of the fetus/child.The financial implications of new surgical treatments.

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.

Current and future antenatal management of isolated congenital diaphragmatic hernia.

Congenital diaphragmatic hernia is surgically correctable, yet the poor lung development determines mortality and morbidity. In isolated cases the outcome may be predicted prenatally by medical imaging. Cases with a poor prognosis could be treated before birth. However, prenatal modulation of lung development remains experimental. Fetoscopic endoluminal tracheal occlusion triggers lung growth and is currently being evaluated in a global clinical trial. Prenatal transplacental sildenafil administration may in due course be a therapeutic approach, reducing the occurrence of persistent pulmonary hypertension, either alone or in combination with fetal surgery.

Quantification of free fetal DNA in multiple pregnancies and relationship with chorionicity.

OBJECTIVE: Free fetal DNA (ffDNA) in the maternal plasma appears to originate mainly from the trophoblast. We tested the hypothesis that ffDNA concentration is increased in multiple pregnancies where trophoblastic mass has been shown to be increased. METHODS: Quantitative real-time PCR was used to measure the plasma concentration of DYS14 in singleton and twin pregnancies with one or two male fetuses. Royston and Wright's regression method was used to relate ffDNA to gestational age in singleton controls; z-scores were calculated for the multiple pregnancy subgroups. RESULTS: Fifty-five singleton and 65 twin pregnancies (36 with one and 29 with two male fetuses) were analysed. There was significantly higher ffDNA concentration in twin pregnancies with two male fetuses compared with pregnancies with one male fetus. In cases with two male fetuses, there was no statistically significant difference between monochorionic and dichorionic pregnancies. CONCLUSIONS: There is higher ffDNA concentration in multiple pregnancies, and this must be taken into account for future quantitative ffDNA applications.

Amniotic fluid index in low-risk, post-dates pregnancies.

OBJECTIVE: To determine normal values for amniotic fluid index (AFI) in uncomplicated post-dates singleton pregnancies and compare it to current reference ranges. POPULATION: Four hundred and forty-eight women with singleton, uncomplicated pregnancies, presenting for post-dates assessment (gestation 40+0 to 42+0 weeks) between January 1, 2004 and June 30, 2005. METHODS: Ultrasound assessment of liquor to calculate the AFI. RESULTS: The mean and standard deviation for AFI in the sample was 9.86 (SD 3.4), which is significantly different to the mean of the currently used reference range (mean 11.6, SD 3.9, p < 0.0001). The 5th percentile in this population was 4.6 cm. CONCLUSIONS: This study has demonstrated lower mean and 5th percentile values for AFI in post-dates pregnancies than current reference ranges. It has the largest published UK study population, and can therefore be used as a reference range in similar populations, which is likely to reduce unnecessary obstetric interventions.

The SAFE project: towards non-invasive prenatal diagnosis.

After the revolutionary detection of ffDNA (free fetal DNA) in maternal circulation by real-time PCR in 1997 and advances in molecular techniques, NIPD (non-invasive prenatal diagnosis) is now a clinical reality. Non-invasive diagnosis using ffDNA has been implemented, allowing the detection of paternally inherited alleles, sex-linked conditions and some single-gene disorders and is a viable indicator of predisposition to certain obstetric complications [e.g. PET (pre-eclampsia)]. To date, the major use of ffDNA genotyping in the clinic has been for the non-invasive detection of the pregnancies that are at risk of HDFN (haemolytic disease of the fetus and newborn). This has seen numerous clinical services arising across Europe and many large-scale NIPD genotyping studies taking place using maternal plasma. Because of the interest in performing NIPD and the speed at which the research in this area was developing, the SAFE (Special Non-Invasive Advances in Fetal and Neonatal Evaluation) NoE (Network of Excellence) was founded. The SAFE project was set up to implement routine, cost-effective NIPD and neonatal screening through the creation of long-term partnerships within and beyond the European Community and has played a major role in the standardization of non-invasive RHD genotyping. Other research using ffDNA has focused on the amount of ffDNA present in the maternal circulation, with a view to pre-empting various complications of pregnancy. One of the key areas of interest in the non-invasive arena is the prenatal detection of aneuploid pregnancies, particularly Down's syndrome. Owing to the high maternal DNA background, detection of ffDNA from maternal plasma is very difficult; consequently, research in this area is now more focused on ffRNA to produce new biomarkers.