Variations of cervical head entrapment in vaginal breech births: New insights on how to prevent, manage and resolve.

This paper presents a novel, systematic way to understand the causes of cervical head entrapment in vaginal breech births, and new insights into management. Three different types of cervical head entrapment are described, with detailed illustrations: unpredictable and potentially catastrophic, manageable, and preventable. The first affects preterm and growth-restricted fetuses. The second involves some degree of uterine prolapse. The third may result from prolonged head entrapment at the pelvic inlet, leaving time for cervical contraction or oedematous entrapment. Traditional and innovative strategies to resolve and prevent this complication are described and illustrated, with suggestions for further research.

OptiBreech collaborative care versus standard care for women with a breech-presenting fetus at term: A pilot parallel group randomised trial to evaluate the feasibility of a randomised trial nested within a cohort.

OptiBreech collaborative care is a multi-disciplinary care pathway for breech presentation at term, with continuity from a breech specialist midwife, including where chosen, for vaginal breech birth (VBB). Pilot randomised trial using unblinded 1:1 parallel group allocation to OptiBreech versus standard care, within a cohort. Participants were women with a breech-presenting fetus > 33 weeks, at four sites in England, January-June 2022. A two-stage consent process was used. Participants consented to undergo random selection to be offered a 'new care process', with a choice to accept it, or not. Primary objectives were to identify recruitment, acceptance, and attrition rates. Randomisation procedures and potential primary outcomes for a substantive study were also feasibility-tested. 68 women were randomised between January-June 2022. The consent process was acceptable to participants, but randomisation was unacceptable to women who specifically sought OptiBreech care. Two women withdrew due to concerns about sharing personal information. More women planned a VBB when randomised to OptiBreech Care (23.5% vs 0, p = .002, 95% CI = 9.3%,37.8%). Women randomised to OptiBreech care had: lower rates of cephalic presentation at birth (38.2% vs 54.5%), higher rates of vaginal birth (32.4% vs 24.2%), lower rates of in-labour caesarean birth (20.6% vs 36.4%), lower rates of neonatal intensive care (5.9% vs 9.1%), and lower rates of severe neonatal morbidity (2.9% vs 9.1%). Randomisation was stopped on the advice of the steering committee before the planned sample of 104, as lack of access to VBB within standard care prohibited comparison of outcomes. Demand for VBB is sufficient for a cohort study, but comparison of outcomes by 1:1 randomisation is not feasible. OptiBreech care would be best evaluated using stepped wedge cluster randomisation. Funded by the United Kingdom National Institute for Health and Care Research (NIHR300582). Clinical trial registration: ISRCTN 14521381.

What are women's experiences of seeking to plan a vaginal breech birth? A systematic review and qualitative meta-synthesis.

Background: Guidelines for breech management at term emphasise choice and informed decision-making. Despite this, the choice of vaginal breech birth (VBB), is not always available or accessible. We aimed to describe the experiences of women seeking a VBB as reported in primary research and to offer strategies for improving this experience that are grounded in evidence. Methods: We conducted a systematic review and qualitative meta-synthesis of the results, using grounded theory analysis methods (PROSPERO registration CRD42021262380), with literature published between January 2000 and February 2022. Seven databases were searched. Our review included literature about women with breech presentation, who sought a planned or unplanned VBB. Studies considering only experiences of alternative management (e.g. caesarean, external cephalic version), and those investigating healthcare workers' experiences were excluded. Covidence systematic review software was used for screening and quality assessment. Qualitative data were extracted using NVivo software (20.5.0). Data were analysed through an iterative process based on constant comparison methods, with an iterative and reflexive code generation process. Codes were then arranged into 'categories of experience', which gave rise to over-arching themes. Results: Our review included 19 studies. We present one overarching theory: 'Women who wish to plan a vaginal breech birth seek connected autonomy'. Our schematic, depicting this theory, includes seven main categories of experience: paternalistic healthcare; emotional turmoil; judgement and self-doubt; mother vs society: refusing to conform; isolated but united by breech; welcomed direction; and supported self-determination and self-efficacy. Conclusions: Women seeking to plan a VBB feel vulnerable and wish to connect with capable and confident healthcare providers. To meet their needs, services should be designed so that they can connect with clinicians who are willing and able to support their autonomy. Services should also seek to limit their exposure to disrespectful and judgemental interactions with healthcare providers.

Members of our public involvement and engagement group and some participants in the OptiBreech research reported difficulty in attempts to access supportive care when trying to plan a vaginal breech birth. This conflicts with national guidance, which emphasises choice and informed decision-making. We wanted to understand more about the experience of seeking to plan a vaginal breech birth, so we searched for research on this topic. We made a careful plan before we started and registered this plan. We searched seven online databases for literature published between January 2000 and February 2022. We focused on studies about women pregnant with breech babies, who sought to plan a vaginal breech birth or whose baby was discovered to be breech in labour. We used Covidence systematic review software to organise and assess the quality of the research we collected. We gathered main themes and illustrative quotes from all of the papers and compared these. We met frequently to discuss our observations and to agree on how we would summarise information we gathered. We agreed that, overall, women who wanted to plan a vaginal breech birth felt vulnerable. They wanted to connect to confident, capable healthcare providers who could help them achieve a vaginal birth as safely as possible: 'connected autonomy.' But their actual experiences ranged widely, including: paternalistic healthcare; emotional turmoil; judgement and self-doubt; mother vs society: refusing to conform; isolated but united by breech; welcomed direction; and supported self-determination and self-efficacy. We concluded that, to meet the needs of women who wish to plan a vaginal breech birth, services should be designed so that they can connect with clinicians who are willing and able to support their autonomy. Services should also limit their exposure to disrespectful and judgemental interactions with healthcare providers.

Not too fast, not too slow: A review of historical trends in vaginal breech time management.

PROBLEM: A lack of consistent professional guidance on when to intervene during emergence (buttocks and anus visible at the introitus to birth of the head) in vaginal breech birth (VBB). BACKGROUND: Hypoxia and asphyxia are common complications of VBB, especially due to umbilical cord compression around the time of emergence. AIM: To gain insight into VBB time management trends, the evidence behind these practices and how they may have influenced outcomes. METHODS: Literature review of obstetric textbooks published between 1960 and 2000 contained in the Wellcome Collection and Royal College of Obstetricians and Gynaecologists Library in London. FINDINGS: 90 textbooks were reviewed. Recommendations for 'safe' intervals between birth of the umbilicus and the head ranged from 5 to 20 min. Many sources focused only on the time required to deliver the head, with 'up to 10 min' being the most common interval described. The review found no mention of cord compression causing concern earlier in breech births than once the umbilicus itself is delivered, nor any evidence to support the recommendations. DISCUSSION: These findings demonstrate a long-term pattern across the second half of the 20th century, whereby birth attendants were urged not to rush emergence nor delay intervention but were given little clear guidance on optimal timings. CONCLUSION: Clear, evidence-based guidance should be provided in breech training materials to avoid unnecessary hypoxic injuries, and this guidance should be rigorously evaluated.

The feasibility of team care for women seeking to plan a vaginal breech birth (OptiBreech 1): an observational implementation feasibility study in preparation for a pilot trial.

BACKGROUND: OptiBreech Care is a care pathway for breech presentation at term, including where chosen, physiological breech birth attended by professionals with advanced training and/or proficiency. We aimed to assess the feasibility of implementing OptiBreech team care prior to proceeding with a planned pilot randomised controlled trial. METHODS: Our design was an observational implementation feasibility assessment across England and Wales, January 2021-June 2022. Our objectives were to determine whether Trusts could provide attendants with advanced training (implementation feasibility), who deliver protocol-consistent care (fidelity), within existing resources (costs), while maintaining low neonatal admission rates (safety) and adequate recruitment rates (trial feasibility). Participants included women > 37 weeks pregnant with a breech-presenting foetus, requesting support for a vaginal breech birth following standard counselling, and staff involved in the study. No randomisation occurred in this first stage of feasibility work. RESULTS: Thirteen National Health Service sites were recruited. A total of 82 women planned births in the study. Sites with a breech specialist midwife recruited at double the rate of sites without (0.90/month, 95% CI 0.64-1.16 vs 0.40, 95% CI 0.12-0.68). Referrals into the study came from midwives (46%), obstetricians (34%) and women themselves (20%). Vaginal births were attended by staff with OptiBreech training at 87.5% (35/40, 95% CI 0.732-0.958) and by staff who met additional proficiency criteria at 67.5% (27/40, 95% CI 0.509-0.814). Fidelity criteria were more consistently met by staff who also met proficiency criteria. There were four neonatal admissions (4.9%, 4/82), including one serious adverse outcome (1.2%, 1/82). CONCLUSIONS: A prospective observational cohort of OptiBreech collaborative care, which could potentially support nested or cluster randomisation, appears feasible in sites willing to establish a dedicated clinic and strategically develop further proficient members of staff, with back-up plans for supporting rapidly progressing births. Randomisation procedures remain to be feasibility tested. It is funded by the NIHR (NIHR300582).

Barriers and facilitators to the implementation of midwife-led care for childbearing women in low- and middle-income countries: A mixed-methods systematic review.

BACKGROUND: Evidence from high-income countries demonstrate improvements in maternal and neonatal health with midwife-led care. Midwife-led care is pivotal to meet the United Nations' Sustainable Development Goals. Despite this, successful implementation of midwife-led care in low- and middle-income countries (LMICs) has been limited. It is therefore necessary to understand the factors that influence the implementation of midwife-led care. AIM: This systematic review aimed to synthesize the evidence on barriers and facilitators to the implementation of midwife-led care for childbearing women in LMICs from the perspectives of care recipients, providers and wider stakeholders. METHODS: A mixed-methods systematic review was conducted of primary research studies that expressed the views of those involved in or affected by the implementation of midwife-led care in LMICs. Reporting followed PRISMA guidelines. MEDLINE, EMBASE, PsychINFO, CINAHL, Maternity and Infant Care database (MIDIRS), Global Health and Web of Science databases were systematically searched. Methodological quality was assessed using the Mixed Methods Appraisal Tool (MMAT). Data was analysed and synthesized using the Supporting the Use of Research Evidence (SURE) framework to identify barriers and enabling factors to implementing midwife-led care. FINDINGS: A total of 31 studies from 21 LMICs were included. At the care recipient level, women need adequate knowledge and confidence about midwife-led care to utilise services. At the care provider level, strengthening midwifery education and practice by employing experienced educators and supervisors is essential. Findings also suggest that increased collaboration between funders, professional organisations, practitioners, communities, and the government is necessary for successful implementation. However, adequate and sustained funding for midwife-led care programs is often lacking and political instability contributes to poor implementation in LMICs. CONCLUSION AND IMPLICATIONS FOR PRACTICE AND RESEARCH: There are several enabling factors which increase the success and sustainability of the midwife-led model of care in LMICs. However, current practice guidelines and strategic frameworks need to better reflect the infrastructure and resource limitations of health settings in LMICs.

A Dynamic Analysis of Conspiratorial Narratives on Twitter During the Pandemic.

Since the breakout of COVID-19 in late 2019, various conspiracy theories have spread widely on social media and other channels, fueling misinformation about the origins of COVID-19 and the motives of those working to combat it. This study analyzes tweets (N = 313,088) collected over a 9-month period in 2020, which mention a set of well-known conspiracy theories about the role of Bill Gates during the pandemic. Using a topic modeling technique (i.e., Biterm Topic Model), this study identified ten salient topics surrounding Bill Gates on Twitter, and we further investigated the interactions between different topics using Granger causality tests. The results demonstrate that emotionally charged conspiratorial narratives are more likely to breed other conspiratorial narratives in the following days. The findings show that each conspiracy theory is not isolated by itself. Instead, they are highly dynamic and interwoven. This study presents new empirical insights into how conspiracy theories spread and interact during crises. Practical and theoretical implications are also discussed.

Breech specialist midwives and clinics in the OptiBreech Trial feasibility study: An implementation process evaluation.

BACKGROUND: Attendance of skilled and experienced professionals at breech births has been associated with a reduction in adverse perinatal outcomes. We aimed to determine whether United Kingdom National Health Service (NHS) sites could reliably provide attendants with OptiBreech training and/or advanced proficiency (intervention feasibility) and consistent care (fidelity) that meets women's needs (acceptability), with low neonatal admission rates (safety) and recruitment adequate to support a clinical trial (trial feasibility). METHODS: Mixed methods implementation evaluation was used. Settings were 13 services in England and Wales. Participants were 82 women requesting support for a vaginal breech birth (VBB) at term. Outcomes were descriptively analyzed. Twenty-one women were interviewed, and transcripts were analyzed using the Theoretical Framework of Acceptability. Iterative analysis informed subsequent interviews and the ongoing process of implementation across sites. RESULTS: Although we initially suggested multidisciplinary teams, actively recruiting Trusts yielded services where VBB care was provided through a dedicated clinic, organized and delivered primarily by a lead midwife who functioned as a specialist. This model achieved 87.5% fidelity with the intervention's goal of ensuring the attendance of OptiBreech-trained professionals. Neonatal outcomes remained stable, with an admission rate of 5.5%. Women reported care from specialist midwives as highly acceptable, but the model is vulnerable without a strategic effort to develop additional proficient team members. CONCLUSIONS: Dedicated clinics coordinated by specialist midwives appear to be an acceptable and feasible implementation strategy to test the safety and effectiveness of proficient team care for VBB in a clinical trial. Back-up arrangements should be maintained while additional members of the team develop proficiency.

Toroidal nuclei of columnar lyotropic chromonic liquid crystals coexisting with an isotropic phase.

Nuclei of ordered materials emerging from the isotropic state usually show a shape topologically equivalent to a sphere; the well-known examples are crystals and nematic liquid crystal droplets. In this work, we explore experimentally and theoretically the toroidal in shape nuclei of columnar lyotropic chromonic liquid crystals coexisting with the isotropic phase. The geometry of these toroids depends strongly on concentrations of the disodium cromoglycate (DSCG) and the crowding agent, polyethylene glycol (PEG). High concentrations of DSCG and PEG result in thick toroids with small central holes, while low concentrations yield thin toroids with wide holes. The multitude of the observed shapes is explained by the balance of bending elasticity and anisotropic interfacial tension.

Development of a core outcome set for effectiveness studies of breech birth at term (Breech-COS)-an international multi-stakeholder Delphi study: study protocol.

BACKGROUND: Women pregnant with a breech-presenting foetus at term are at increased risk of adverse pregnancy outcomes. The most common intervention used to improve neonatal outcomes is planned delivery by caesarean section. But this is not always possible, and some women prefer to plan a vaginal birth. A number of providers have proposed alternative interventions, such as delivery protocols or specialist teams, but heterogeneity in reported outcomes and their measurements prevents meaningful comparisons. The aim of this paper is to present a protocol for a study to develop a Breech Core Outcome Set (Breech-COS) for studies evaluating the effectiveness of interventions to improve outcomes associated with term breech birth. METHODS: The development of a Breech-COS includes three phases. First, a systematic literature review will be conducted to identify outcomes previously used in effectiveness studies of breech birth at term. A focus group discussion will be conducted with the study's pre-established Patient and Public Involvement (PPI) group, to enable service user perspectives on the results of the literature review to influence the design of the Delphi survey instrument. Second, an international Delphi survey will be conducted to prioritise outcomes for inclusion in the Breech-COS from the point of view of key stakeholders, including perinatal care providers and families who have experienced a term breech pregnancy. Finally, a consensus meeting will be held with stakeholders to ratify the Breech-COS and disseminate findings for application in future effectiveness studies. DISCUSSION: The expectation is that the Breech-COS will always be collected in all clinical trials, audits of practice and other forms of observation research that concern breech birth at term, along with other outcomes of interest. This will facilitate comparing, contrasting and combining studies with the ultimate goal of improved maternal and neonatal outcomes. TRIAL REGISTRATION: Core Outcome Measures in Effectiveness Trials (COMET) #1749.

Optimal time intervals for vaginal breech births: a case-control study.

Background: Breech births are associated with a high rate of hypoxic injury, in part due to cord occlusion during emergence. Maximum time intervals and guidelines oriented toward earlier intervention have been proposed in a Physiological Breech Birth Algorithm. We wished to further test and refine the Algorithm for use in a clinical trial. Methods: We conducted a retrospective case-control study in a London teaching hospital, including 15 cases and 30 controls, during the period of April 2012 to April 2020. Our sample size was powered to test the hypothesis that exceeding recommended time limits is associated with neonatal admission or death. Data collected from intrapartum care records was analysed using SPSS v26 statistical software. Variables were intervals between the stages of labour and various stages of emergence (presenting part, buttocks, pelvis, arms, head). The chi-square test and odds ratios were used to determine association between exposure to the variables of interest and composite outcome. Multiple logistic regression was used to test the predictive value of delays defined as non-adherence the Algorithm. Results: Logistic regression modelling using the Algorithm time frames had an 86.8% accuracy, a sensitivity of 66.7% and a specificity of 92.3% for predicting the primary outcome. Delays between umbilicus and head >3 minutes (OR: 9.508 [95% CI: 1.390-65.046] p=0.022) and from buttocks on the perineum to head >7 minutes (OR: 6.682 [95% CI: 0.940-41.990] p=0.058) showed the most effect. Lengths of time until the first intervention were consistently longer among the cases. Delay in intervention was more common among cases than head or arm entrapment. Conclusion: Emergence taking longer than the limits recommended in the Physiological Breech Birth algorithm may be predictive of adverse outcomes. Some of this delay is potentially avoidable. Improved recognition of the boundaries of normality in vaginal breech births may help improve outcomes.

When babies are born bottom-first, there is a risk that the baby could be starved of oxygen during the birth. To help prevent this, researchers developed a flowchart to guide when to help a baby out, the Physiological Breech Birth Algorithm. The first version was based on a study of actual breech birth videos and recommends that the birth should be complete within 7-5-3 minutes from buttocks-pelvis-umbilicus visible. This is different from current national guidance not to intervene until 5 minutes after the baby's pelvis is born. We are using this new algorithm to guide midwives and doctors in the OptiBreech Care Trial, so we wanted to make sure it is safe and accurate.

Ion-dependent DNA configuration in bacteriophage capsids.

Bacteriophages densely pack their long double-stranded DNA genome inside a protein capsid. The conformation of the viral genome inside the capsid is consistent with a hexagonal liquid crystalline structure. Experiments have confirmed that the details of the hexagonal packing depend on the electrochemistry of the capsid and its environment. In this work, we propose a biophysical model that quantifies the relationship between DNA configurations inside bacteriophage capsids and the types and concentrations of ions present in a biological system. We introduce an expression for the free energy that combines the electrostatic energy with contributions from bending of individual segments of DNA and Lennard-Jones-type interactions between these segments. The equilibrium points of this energy solve a partial differential equation that defines the distributions of DNA and the ions inside the capsid. We develop a computational approach that allows us to simulate much larger systems than what is possible using the existing molecular-level methods. In particular, we are able to estimate bending and repulsion between the DNA segments as well as the full electrochemistry of the solution, both inside and outside of the capsid. The numerical results show good agreement with existing experiments and with molecular dynamics simulations for small capsids.

Cultivating awareness of sexual and gender diversity in a midwifery curriculum.

OBJECTIVE: To explore the perspectives of student midwives, midwifery educationalists and midwifery clinicians from and connected to one University in order to identify strategies to enhance awareness of sexual and gender diversity in a pre- registration midwifery curriculum. DESIGN: A mixed method study including an online survey and a series of focus groups Setting: One University in London Participants: 47 survey respondents and 16 focus group participants Findings: Two Inductive themes were developed from the data analysis: Practising Open Mindedness and Cultivating Openness and four sub themes; Making Assumptions, Developing self- awareness, Challenge and Discomfort and Safe spaces. Participants proposed learning strategies that they thought would facilitate cultivating openness and open mindedness.

Development of a core outcome set for effectiveness studies of breech birth at term (Breech-COS): A systematic review on variations in outcome reporting.

Women pregnant with a breech-presenting fetus at term are at an increased risk of adverse outcomes. Although the most common intervention is planned delivery by caesarean section, this is not always possible or desirable. Comparing alternative interventions is difficult due to heterogeneity in reported outcomes and their measurements. Additionally, the evidence, particularly for women in labour with a breech-presenting fetus, is very low quality, with several outcomes viewed as critical and important to decision-making not reported at all. There is a need to develop a core outcome set of minimum outcomes in all studies evaluating the effectiveness of interventions to improve outcomes associated with term breech birth (Breech-COS). Our objectives were to (1) identify outcomes currently reported in effectiveness studies of breech birth at term using a systematic review of the literature; (2) assess the methodological quality of outcome reporting in the included studies; and (3) engage with members of an established Patient and Public Involvement (PPI) group about the results, to help frame our understanding from the perspective of service users. We searched three databases (MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials) for all effectiveness studies associated with vaginal breech birth published in English between 2000 and 2020. Two reviewers independently screened and extracted the data. Outcomes were categorised into neonatal, maternal, features of labour, and long-term maternal and hierarchy of outcome classification (primary, secondary, part of composite, or undesignated). Frequency of reporting was calculated for each. An adapted methodological assessment was done for each study investigating whether primary and secondary objectives were clearly stated and defined. The results of the systematic review were then discussed with a PPI group to consider importance and relevance to service users. A total of 211 outcomes were extracted from 108 included studies, comprising of short (43) and long-term (39) neonatal, short (54) and long-term (39) maternal and features of labour (36) outcomes. The most frequently reported outcome in each category was: APGAR score at 5 min, developmental vulnerability/neurological morbidity, maternal mortality, urinary incontinence, and actual mode of birth respectively. Long-term outcomes were infrequently reported in the included studies, with outcomes for future pregnancies not reported at all, although these were each deemed important by service users. There was a lack of consensus in definition and measurement of outcomes, with only 36% of the included studies having clearly stated primary and secondary objectives. The observed heterogeneity in reported outcomes, lack of consensus in definition and measurement, as well as desire expressed by service users to have robust risk statistics for outcomes important to them highlights the need to develop a core outcome set for evaluating effectiveness studies of breech birth at term. A Breech-COS will enable useful synthesis of evidence and contribute to supported decision-making for women pregnant with a breech-presenting fetus at term.

Physiological breech birth training: An evaluation of clinical practice changes after a one-day training program.

BACKGROUND: The "physiological breech birth" one-day training program is based on evidence about the physiology of breech births and how clinicians learn breech skills. Previous evaluations have demonstrated positive effects on confidence and knowledge, but the training's effect on clinical practice and outcomes is unknown. METHODS: A mixed-methods evaluation was conducted in eight National Health Service hospitals in England and Northern Ireland. Changes in confidence and knowledge were assessed using pretraining and post-training surveys. Mode of birth and maternal birth positions were evaluated using audit data covering one year before the training and one year after, for all singleton vaginal breech births at term. FINDINGS: A total of 263 participants completed the surveys. Confidence in managing breech births in both upright and supine positions significantly increased, as did participant knowledge. Audited data for 1402 women were collected. Overall vaginal birth rates remained similar in both periods. Among singleton vaginal breech births >37 weeks, the use of upright birthing positions increased significantly (P = .002). The study was not powered to detect differences in other outcomes, but pilot data were collected to inform the design of future studies. CONCLUSIONS: Increase in use of upright birthing positions suggests that physiological breech birth training is likely to lead to clinical practice changes, which may help support maternal choice in line with current guidance. However, provision of a one-day training program did not change overall vaginal breech birth rates. Adequately powered research is needed to determine effects of clinical practice changes on clinical outcomes.

Face-to-pubes rotational maneuver for bilateral nuchal arms in a vaginal breech birth, resolved in an upright maternal position: A case report.

BACKGROUND: A physiological breech birth is one in which the woman is encouraged to remain active throughout her labor and able to assume the position of her choice for the birth. Use of this strategy within the United Kingdom National Health Service has led to the use of innovative maneuvers to relieve obstruction when women give birth in upright positions, for example, kneeling or standing. This includes use of the face-to-pubes rotational maneuver to relieve extended nuchal arm(s). In this paper, we report a case where the face-to-pubes rotational maneuver was used to relieve bilateral nuchal arm entrapment in a breech birth. METHODS: Single-case study. We aimed to generate an in-depth understanding of how this maneuver works and how professionals decide to use it by exploring its use in a real-life context. RESULTS: The face-to-pubes rotational maneuver appears to be an effective method of relieving nuchal arm entrapment when used by experienced hands. In cases of bilateral nuchal arm entrapment, elevation to a higher station may be necessary to dis-impact the arms above the pelvic inlet before the fetus can be rotated. After face-to-pubes rotation and release of arms, the head should be realigned in an occiput anterior position for delivery. CONCLUSION: The face-to-pubes rotational maneuver can be taught for resolution of nuchal arms in an upright position. Parents should be informed of the availability or not of a specialist midwife trained in physiological breech birth, as this may be important to their decision-making.

Fine structure of viral dsDNA encapsidation.

Unraveling the mechanisms of packing of DNA inside viral capsids is of fundamental importance to understanding the spread of viruses. It could also help develop new applications to targeted drug delivery devices for a large range of therapies. In this article, we present a robust, predictive mathematical model and its numerical implementation to aid the study and design of bacteriophage viruses for application purposes. Exploiting the analogies between the columnar hexagonal chromonic phases of encapsidated viral DNA and chromonic aggregates formed by plank-shaped molecular compounds, we develop a first-principles effective mechanical model of DNA packing in a viral capsid. The proposed expression of the packing energy, which combines relevant aspects of the liquid crystal theory, is developed from the model of hexagonal columnar phases, together with that describing configurations of polymeric liquid crystals. The method also outlines a parameter selection strategy that uses available data for a collection of viruses, aimed at applications to viral design. The outcome of the work is a mathematical model and its numerical algorithm, based on the method of finite elements, and computer simulations to identify and label the ordered and disordered regions of the capsid and calculate the inner pressure. It also presents the tools for the local reconstruction of the DNA "scaffolding" and the center curve of the filament within the capsid.

Practical insight into upright breech birth from birth videos: A structured analysis.

BACKGROUND: We aimed to identify common features of upright vaginal breech births with good outcomes to refine a physiological approach to teaching breech birth. METHODS: We performed a structured analysis of 42 videos of successful upright breech births (eg, kneeling, hand/knees), facilitated by obstetricians (n = 34) and midwives (n = 8) in nine different countries. Precise timings and relevant clinical details were recorded on an Excel spreadsheet. Each video was analyzed twice by at least two members of the research team. Time-to-event intervals, frequencies of interventions, and descriptive statistics were calculated using SPSS. RESULTS: A completely spontaneous (labor mechanisms and maternal effort only) birth occurred in 14/42 (33%) cases. The median time between the birth of the fetal pelvis and the head in all births was 1:52 (IQR 1:05,2:46; min:sec). Lack of spontaneous rotation to a sacro-anterior position by the time the fetus had emerged to the nipple line was strongly associated with fetal arm entrapment. The following maneuvers were used: shoulder press to flex the aftercoming head in midpelvis or outlet (n = 24), sweeping down arm/s (n = 12), buttock lift to assist shoulder press (n = 6), modified Mauriceau (n = 6), rotational maneuvers to release an entrapped arm (n = 6), elevate and rotate fetal head to assist engagement (n = 2), and conversion into supine maternal position (n = 2). CONCLUSIONS: Most upright breech births occur within 3 minutes of the birth of the fetal pelvis. Upright breech birth attendants use variations of traditional maneuvers. We introduce a physiological breech algorithm as an initial timekeeping framework for teaching, research, and practice.