Introduction: Simulation has assumed an integral role in the Canadian healthcare system with applications in quality improvement, systems development, and medical education. High quality simulation-based research (SBR) is required to ensure the effective and efficient use of this tool. This study sought to establish national SBR priorities and describe the barriers and facilitators of SBR in Emergency Medicine (EM) in Canada. Methods: Simulation leads (SLs) from all fourteen Canadian Departments or Divisions of EM associated with an adult FRCP-EM training program were invited to participate in three surveys and a final consensus meeting. The first survey documented active EM SBR projects. Rounds two and three established and ranked priorities for SBR and identified the perceived barriers and facilitators to SBR at each site. Surveys were completed by SLs at each participating institution, and priority research themes were reviewed by senior faculty for broad input and review. Results: Twenty SLs representing all 14 invited institutions participated in all three rounds of the study. 60 active SBR projects were identified, an average of 4.3 per institution (range 0-17). 49 priorities for SBR in Canada were defined and summarized into seven priority research themes. An additional theme was identified by the senior reviewing faculty. 41 barriers and 34 facilitators of SBR were identified and grouped by theme. Fourteen SLs representing 12 institutions attended the consensus meeting and vetted the final list of eight priority research themes for SBR in Canada: simulation in CBME, simulation for interdisciplinary and inter-professional learning, simulation for summative assessment, simulation for continuing professional development, national curricular development, best practices in simulation-based education, simulation-based education outcomes, and simulation as an investigative methodology. Conclusion: Conclusion: This study has summarized the current SBR activity in EM in Canada, as well as its perceived barriers and facilitators. We also provide a consensus on priority research themes in SBR in EM from the perspective of Canadian simulation leaders. This group of SLs has formed a national simulation-based research group which aims to address these identified priorities with multicenter collaborative studies.

Introduction: Different tools have been developed to complement medical training, and improve student learning. Although social media has been described as an innovative educational strategy, evidence for its use is scarce in emergency medicine (EM). The primary outcome of this study was to evaluate whether brief teaching points (tweets) sent to medical students (MS) via a Twitter feed, would yield better exam score at the end of an emergency medicine (EM) rotation. Methods: Participants included in this prospective cohort study were MS completing an EM rotation at our tertiary care academic center. The control group was recruited from December 2016 to November 2017 and the experimental group from November 2017 to November 2018. The MS in the experimental group were invited to follow a Twitter feed. A total of 32 EM-related tweets based on learning objectives were sent out throughout the 4 week rotation. At the end of the rotation, MS of both cohorts took an exam and completed a survey of assiduity and appreciation. Exam scores were compared using t-tests. Results: A total of 80 MS were recruited for the study, 38 in the experimental cohort. Average exam scores were similar in both cohorts (control = 63 ± 9% vs experimental = 64 ± 8% for a mean difference of -2% [95%CI -6 to 2], p = 0.37). Of the experimental group, only 7 (18%) of the participants reported viewing more than 50% of the tweets. There was no difference between mean exam scores of this sub-group and that of the control cohort (66 ± 10% for a mean difference of 4% [95%CI -4 to 11], p = 0.33). The majority (n = 20, 53%) of the MS in the experimental cohort did not read any tweets. When compared to the rest of the experimental cohort MS who reported viewing ≥50% of the tweets found the Twitter feed to be a useful educational tool. Indeed, on a 3 item Likert scale used to evaluate different aspects of appreciation, they found the Twitter feed to be beneficial to their rotation (86% vs 13%, p < 0.001) as well as helpful in patient management (71% vs 16%, p = 0.001). These same MS would have liked more tweets (100% vs 19%, p < 0.001) and would like to use Twitter in other rotations (100% vs 32%, p = 0.005). Conclusion: In this study, there was no difference in the exam scores between MS having access to regular EM-focused educational tweets in comparison to those who did not. Results also found a lower than expected assiduity of MS to the educational Twitter feed, although those who used it significantly found it useful.

This paper examines the nineteenth-century census as an early information technology and a medium for the transnational exchange of ideas in the nineteenth century. In particular, it considers how the ideas discussed by the International Statistical Congresses were directly applied in the newly established kingdom of Bulgaria in the first censuses from 1881 to 1888. It then examines how the legacy of Ottoman rule and the categories of the nineteenth-century Ottoman censuses unconsciously influenced the first census of Bulgaria, despite the desire of the new rulers to mark a significant break with the past. It also demonstrates how the nationalist feeling in the multiethnic former territory of the Ottoman Empire influenced the seemingly neutral categories of the first census. These categories then began to produce an implicit representation of the ideal Bulgarian citizen and so started the process of exclusion of the Turkish-speaking or Muslim population from full membership of the new body politic.

The ability to predict the fertility of bulls before semen is released into the field has been a long-term objective of the animal breeding industry. However, the recent shift in the dairy industry towards the intensive use of young genomically selected bulls has increased its urgency. Such bulls, which are often in the highest demand, are frequently only used intensively for one season and consequently there is limited time to track their field fertility. A more pressing issue is that they produce fewer sperm per ejaculate than mature bulls and therefore there is a need to reduce the sperm number per straw to the minimum required without a concomitant reduction in fertility. However, as individual bulls vary in the minimum number of sperm required to achieve their maximum fertility, this cannot be currently achieved without extensive field-testing. Although an in vitro semen quality test, or combination of tests, which can accurately and consistently determine a bull’s fertility and the optimum sperm number required represent the ‘holy grail’ in terms of semen assessment, this has not been achieved to date. Understanding the underlying causes of variation in bull fertility is a key prerequisite to achieving this goal. In this review, we consider the reliability of sire conception rate estimates and then consider where along the pregnancy establishment axis the variation in reproductive loss between bulls occurs. We discuss the aetiology of these deficiencies in sperm function and propose avenues for future investigation.

Introduction: Pediatric pain is often under-treated in emergency departments (EDs), which is known to cause short and long-term harm. A recent quality improvement collaborative (QIC) was successful in improving treatment of children’s pain across 4 EDs in our city. A new QIC was then formed among EDs across our province to improve treatment of presenting and procedural pain. Aims were to improve the proportion of children <12 years of age who receive topical anesthetic before needle procedures from 13% to 50%; and for children <17 years of age with fractures: to 1) improve the proportion who receive analgesic medication from 35% to 50%; 2) improve the proportion who have a documented pain score from 23% to 50%, and 3) reduce median time to analgesia from 59 minutes to 30 minutes, within 1 year. Methods: Invitations to participate in the QIC were sent to all 113 EDs in the province that treat children and had not participated in the previous QIC. Each site was asked to form a project team, participate in monthly webinars, develop key driver diagrams and project aims, undertake PDSA tests of change, and audit charts to assess performance. Sites are given a list of 20 randomly selected charts per month for audit. Audit data was entered into REDCap and uploaded to a provincial run chart dashboard. All participating sites received a “comfort kit” consisting of distraction items for children as well as educational materials. Measures of presenting pain included proportion of children <17 years with a diagnosis of fracture who have a documented pain score, proportion who receive an analgesic medication, and minutes to analgesia. The measure for procedural pain was the proportion of children <12 years who receive topical anesthetic prior to a needle procedure for a laboratory test. Length of stay for pediatric patients and all patients were balancing measures. Run charts were used to detect special cause. Difference in proportions were compared using 2. Final analysis will include interrupted time series. Results: 34 of 113 invited sites (30%) agreed to participate, including rural and regional representation from all geographic zones; 4222 visits since June 2016 were analyzed. Implementation began June 2017. Comparing the first 4 months following implementation to the preceding year, the proportion of children receiving topical anesthetic prior to needles increased from 13% to 25% (p<0.001). For children with fractures, the proportion with pain scores increased from 23% to 35% (p<0.001), proportion receiving analgesic medication increased from 35% to 42% (p<0.001), and median minutes to analgesia decreased from 59 to 43. Insufficient time points at this stage preclude identification of special cause. Conclusion: This province-wide QIC has already resulted in significant progress toward aims during the first 4 months of implementation. The QIC approach shows promise for improving pain outcomes in children visiting diverse EDs across a province.

Introduction: Undertreated pain is known to cause short and long-term harm in children. Limb injuries are a common painful condition in emergency department (ED) patients, accounting for 12% of ED visits by children. Our city has one pediatric ED in a freestanding children’s hospital and 3 general ED’s that treat both adults and children. 68% of pediatric limb injuries in our city are treated in the pediatric ED and 32% are treated in a general ED. A quality improvement (QI) initiative was developed at the children’s hospital ED in April 2015 focusing on “Commitment to Comfort.” After achieving aims at the childrens hospital, a QI collaborative was formed among the pediatric ED and the 3 general ED’s to 1) improve the proportion of children citywide receiving analgesia for limb injuries from 27% to 40% and 2) reduce the median time to analgesia from 37 minutes to 15 minutes, during the time period of April-September, 2016. Methods: Data were obtained from computerized order entry records for children 0-17.99 years visiting any participating ED with a chief complaint of limb injury. Project teams from each site met monthly to discuss aims, develop key driver diagrams, plan tests of change, and share learnings. Implementation strategies were based on the Model for Improvement with PDSA cycles. Patient and family consultation was obtained. Process measures included the proportion of children treated with analgesic medication and time to analgesia; balancing measures were duration of triage and length of stay for limb injury and all patients. Site-specific run charts were used to detect special cause variation. Data from all sites were combined at study end to measure city-wide impact using 2 and interrupted time series analysis. Results: During the 3.5-year time period studied (April 1, 2014-September 30, 2017), there were 45,567 visits to the participating ED’s by children 0-17.99 years with limb injury. All visits were included in analysis. Special cause was detected in run charts of all process measures. Interrupted time series analysis comparing the year prior to implementation at the childrens hospital in April 2015 to the year following completion of implementation at the 3 general hospitals in October 2016 demonstrated that the proportion of patients with limb injury receiving analgesia increased from 27% to 40% (p<0.01), and the median time from arrival to analgesia decreased from 37 to 11 minutes (p<0.01). Balancing measure analysis is in progress. Conclusion: This multisite initiative emphasizing “Commitment to Comfort” was successful in improving pain outcomes for all children with limb injuries seen in city-wide ED’s, and was sustained for one year following implementation. A QI collaborative can be an effective method for spreading improvement. The project team is now spreading the Commitment to Comfort initiative to over 30 rural and regional EDs throughout the province through establishment of a provincial QI collaborative.

Introduction: Hospital admission within 72 hours of emergency discharge is a widely accepted measure of emergency department quality of care. Patients returning for unplanned admission may reveal opportunities for improved emergency or followup care. Calgary emergency physicians, however, are rarely notified of these readmissions. Aggregate site measures provide a high level view of readmissions for managers, but dont allow for timely, individual reflection on practice and learning opportunities. These aggregations may also not correctly account for variation in planned readmissions and other workflow nuances. There was a process in place at one facility to compile and communicate readmission details to each physician, but it was manual, provided limited visit detail, and was done weeks or months following discharge. Methods: A new, realtime 72 hour readmission notification recently implemented within the Calgary Zone provides direct and automated email alerts to all emergency physicians and residents involved in the care of a patient that has been readmitted. This alert is sent within hours of a readmission occurring and contains meaningful visit detail (discharge diagnosis, readmit diagnosis, patient name, etc) to help support practice reflection. An average of 15 alerts per day are generated and have been sent since implementation in April, 2017. Although an old technology, the use of email is a central component of the solution because it allows physicians to receive notifications at home and outside the hospital network where they routinely perform administrative tasks. A secondary notification is sent to personal email accounts (Gmail, Hotmail, etc) to indicate an unplanned admission has occurred, but without visit detail or identifiable information. It also allowed implementation with no new hardware or software cost. Results: A simple thumbs up/down rating system is used to adjust the sensitivity of the alert over time. More than 66% of those providing feedback have indicated the alert is helpful for practice reflection (i.e., thumbs up). And of those that indicated it was not helpful, comments were often entered indicating satisfaction with the alert generally, or suggestions for improvement. For example, consulted admitting physicians are often responsible for discharge decisions and should be added as recipients of the alert. Conclusion: Many physicians have indicated appreciation in knowing about return patients, and that they will reflect on their care, further review the chart, or contact the admitting physician for further discussion. Most are accepting of some ‘expected’ or ‘false positive’ alerts that aren’t helpful for practice reflection. Further tuning and expansion of the alert to specialist and consult services is needed to ensure all physicians involved in a discharge decision are adequately notified.

Introduction: There is a growing interest in providing clinicians with performance reports via audit and feedback (A&F). Despite significant evidence exists to support A&F as a tool for self-reflection and identifying unperceived learning needs, there are many questions that remain such as the optimal content of the A&F reports, the method of dissemination for emergency physicians (EP) and the perceived benefit. The goal of the project was to 1. evaluate EP perceptions regarding satisfaction with A&F reports and its’ ability to stimulate physicians to identify opportunities for practice change and 2. identify areas for optimization of the A&F reports. Methods: EP practicing at any of the four adult hospital sites in Calgary were eligible. We conducted a web survey using a modified Dillman technique eliciting EP perspectives regarding satisfaction, usefulness and suggestions for improvement regarding the A&F reports. Quantitative data were analyzed descriptively and free-text were subjected to thematic analysis. Results: From 2015 onwards, EP could access their clinical performance data via an online dashboard. Despite the online reports being available, few physicians reviewed their reports stating access and perceived lack of utility as a barrier. In October 2016, we began disseminated static performance reports to all EP containing a subset of 10 clinical and operational performance metrics via encrypted e-mail. These static reports provided clinician with their performance with peer comparator data (anonymized), rationale and evidence for A&F, information on how to use the report and how to obtain continuing medical education credits for reviewing the report. Conclusion: Of 177 EP in Calgary, we received 49 completed surveys (response rate 28%). 86% of the respondents were very/satisfied with the report. 88% of EP stated they would take action based on the report including self-reflection (91%) and modifying specific aspects of their practice (63%). Respondents indicated that by receiving static reports, 77% were equally or more likely to visit the online version of the eA&F tool. The vast majority of EP felt that receiving the A&F reports on a semi-annual basis was preferred. Three improvements were made to the eA&F based on survey results: 1) addition of trend over time data, 2) new clinical metrics, and 3) optimization of report layout. We also initiated a separate, real-time 72-hour bounceback electronic notification system based on the feedback. EP value the dissemination of clinical performance indicators both in static report and dashboard format. Eliciting feedback from clinicians allows iterative optimization of eA&F. Based on these results, we plan to continue to provide physicians with A&F reports on a semi-annual basis.

Up to the 18th century, the prevailing view of reproduction, or ‘generation’ as it was referred to, was that organisms develop from miniatures of themselves, termed preformation. The alternative theory, epigenesis, proposed that the structure of an animal emerges gradually from a relatively formless egg. The teachings of the Ancient Greeks who argued either that both sexes each contributed ‘semen’ to form the embryo, or held a more male-centred view that the female merely provided fertile ground for the male seed to grow, dominated thinking until the 17th century, when the combined work of numerous scholars led to the theory that all female organisms, including humans, produced eggs. The sequence of events leading to the commercial use of artificial insemination (AI) date back to the discovery of sperm in 1678, although it took almost 100 years to demonstrate that sperm were the agents of fertilisation and a further 100 years for the detailed events associated with fertilisation to be elucidated. The first successful AI, carried out in the dog, dates back to 1780 while it was not until the early to mid-1900s that practical methods for AI were described in Russia. Inspired by the Russian success, the first AI cooperative was established in Denmark in 1936 and later in the United States in 1938. The next major advances involved development of semen extenders, addition of antibiotics to semen, and the discovery in 1949 that glycerol protected sperm during cryopreservation. Almost four decades later, the flow cytometric separation of X- and Y-bearing sperm opened a new chapter in the application of AI for cattle breeding. As we look forward today, developments in imaging sperm and breakthroughs in gene editing and stem cell technology are opening up new possibilities to manipulate reproduction in a way never thought possible by the pioneers of the past. This review highlights some of the main milestones and individuals in the history of sperm biology and the development of technologies associated with AI in cattle.

Introduction: To help mitigated risks associated with red blood cell transfusions, CWC guidelines recommend practicing restrictively. Transfusion Medicine recommends using a Hgb threshold of 70 g/L, and ordering a single unit at a time (with reassessment after). The purpose of this study is to investigate Emergency Department (ED) compliance with these more restrictive thresholds among hemodynamically stable patients. Methods: A retrospective analysis was performed on data from all emergency visits to 4 adult urban ED sites from July 1 2014 to July 1 2016. We excluded unstable patients (CTAS1, temperature >38°C, HR >100 bpm, RR >20 rpm, systolic BP <90 mmHg, and O2 sat <85%) and certain others (patients without a Hgb level, patients who left without being seen, and orders cancelled via patient discharge). After applying exclusion factors, we examined transfusions ordered. Appropriateness was assessed using the stratified Choosing Wisely Canada Guidelines for Transfusion. As an adjunct, IV iron therapy data was also analyzed for the same period between July 1 2014 and July 1 2016, excluding patients who did not have a Hgb level. Results: We identified 1329 eligible patients (54% female), with a mean age of 68 and average first hemoglobin of 72 g/L. Across all groups, 16% of patients received only 1 unit of blood. 19% of transfused patients had a hemoglobin less than 60 g/L, 45% had a Hgb <70 g/L, 32% had a Hgb 70-80 g/L, 14% had a Hgb 81-90 g/L, and 8% had a Hgb >90 g/L. Over the same two-year period, 178 patients received IV iron. The average Hgb for those patients was 82 g/L. Conclusion: A retrospective analysis documents a significant likelihood of pRBC over-transfusion among Emergency Department physicians and an underutilization of IV iron therapy for certain hemodynamically stable and anemic patients. The development of audit and feedback methods, and creation of a clinical pathway may help address the rate of over-transfusion.

Early-life nutrition affects calf development and thus subsequent performance. The aim of this study was to examine the effect plane of nutrition on growth, feeding behaviour and systemic metabolite concentrations of artificially reared dairy bull calves. Holstein-Friesian (F; n=42) and Jersey (J; n=25) bull calves with a mean±SD age (14±4.7 v. 27±7.2 days) and BW (47±5.5 v. 33±4.7 kg) were offered a high, medium or low plane of nutrition for 8 weeks using an electronic feeding system which recorded a range of feed-related events. Calves were weighed weekly and plasma samples were collected via jugular venipuncture on weeks 1, 4 and 7 relative to the start of the trial period. The calves offered a high plane of nutrition had the greatest growth rate. However, the increased consumption of milk replacer led to a reduction in feed efficiency. Holstein-Friesian calves offered a low plane of nutrition had the greatest number of daily unrewarded visits to the feeder (P<0.001). β-hydroxybutyrate (BHB) concentrations were greater in F calves on a low plane of nutrition (P<0.001). Although there was no effect of plane of nutrition, BHB concentrations in F calves increased before weaning, concomitant with an increase in concentrate consumption. Urea concentrations were unaffected by plane of nutrition within either breed. Jersey calves on a low plane of nutrition tended to have lower triglycerides than those on a high plane (P=0.08), but greater than those on a medium plane (P=0.08). Holstein-Friesian calves offered a high plane of nutrition tended to have greater triglyceride concentrations than those on a medium plane (P=0.08). Triglycerides increased from the start to the end of the feeding period (P<0.05), across both breeds. A medium plane of nutrition resulted in a growth, feeding behaviour and metabolic response comparable with a high plane of nutrition in pre-weaned bull calves of both F and J breeds.

This article examines the debates and decisions of the military section of the Eighth Party Congress of March 1919, only released in Izvestiia TsK KPSS in 1989-90. It rebuts the standard interpretation of the military section (usually referred to as the Military Opposition) as a minority platform opposed to the use of former tsarist officers in the Red Army, most notably proposed in R. V. Daniels's The Conscience of the Revolution: Communist Opposition in Soviet Russia (1960). Instead, I argue that the debates were more concerned with the military's increasing autonomy at the expense of party control. These fears were compounded by the introduction of the mass conscription of an apolitical peasantry at a time of extreme instability. This indiscriminate conscription had alarmed many Red Army party workers, who were only too aware of the dangers of arming an unconscious peasant mob. In addition, the article lays bare the beginning of the longer-term conflict between Iosif Stalin and Lev Trotskii and demonstrates Stalin's early influence within the party membership.

Introduction: The addition of computerized physician order entry (CPOE) to Emergency Departments in recent years has led to speculation over potential benefits and pitfalls. Recent studies have shown benefits to CPOE, though there lacks sufficient evidence on how it could change physician behaviour. Physician practices are known to be difficult to change, with getting evidence into daily practice being the main challenge of knowledge translation. Our study aims were to determine if well-designed electronic order sets for CPOE improved MD practices. Methods: The Calgary Zone Pain Management in the Emergency Department Working Group relied on a GRADE-based literature review for identifying best practices for analgesia and antiemetics, resulting in soft changes to the dedicated analgesia and antiemetic electronic order set noting working group preference, and emphasizing hydromorphone over morphine, as well as 4 mg ondansetron over 8 mg. The new electronic order set was started in the only Calgary Region order entry system on December 11th, 2014. Data was collected from July 2014 - May 2015. A Yates chi-squared analysis was completed on all orders in a category, as well as the subgroups of ED staff and residents, and orders placed using the new order set. Results: A total of 100460 orders were analyzed. The use of hydromorphone increased significantly across all 4 EDs. IV hydromorphone use increased (5.82% of all opioid orders up to 26.93%, P<0.0001) with a reciprocal decline in IV morphine (67.81% of all opioid orders down to 46.56%, P<0.0001). Similar effects were observed with ondansetron 4 mg IV orders increasing (1.37% of all ondansetron orders to 18.64%, P<0.0001) with a decrease in 8 mg dosing (15.75% of all ondansetron orders to 7.23%, P<0.0001). These results were replicated to a lesser degree in the non-ED staff and non-order set subgroups. Implementation of the new order set resulted in an increase of its use (37.64% of all opioid orders up to 49.29%, P<0.0001). Finally, a cost-savings analysis was completed showing a projected annual savings of $185,676.52 on medications alone. Conclusion: This data supports the manipulation of electronic order sets to help shape physician behaviour towards best practices. This provides another strong argument towards the benefits of CPOE, and can help maintain best practices in Emergency Medicine.

Introduction: The decision to treat with parenteral therapy may reflect a variable practice pattern among emergency physicians and represent an opportunity to standardize care. Our objective was to describe physician level practice variation for IV therapies in patients with low-acuity presentations and quantify the contribution of IV therapy to prolonging ED LOS. Methods: Using administrative data merged with computerized physician order entry information we sampled 48 months of patient variables across four urban EDs (Jan 1, 2014 - Dec 22, 2015). Eligible patients: 1. presented with complaints of abdominal pain, nausea and vomiting or diarrhea or had a discharge diagnosis of cellulitis 2.were in a low acuity category (Canadian Triage and Acuity Scale - CTAS 3 or 4) 3.were triaged to non-stretcher zones of the ED and 4.were not admitted to hospital. The primary outcome was the physician-level variation in the decision to order IV therapies for this patient group; namely one or more of the following: IV fluids, opioid analgesia, anti-emetics and antibiotics. Secondary outcomes were a comparison of ED LOS, ED revisits at 7 days and ED revisits resulting in admission at 7 days for the IV and non-IV groups. Results: Our analysis included 31 802 patient visits treated by 185 physicians. The average patient age was 37.8 years with 64.3% being female and the majority triaged as CTAS 3 (82.5%). On average 24% of these visits were treated with IV therapies; 90th percentile; 34%. For physicians seeing in excess of 100 cases, the variation in IV therapy use ranged from 1% to 47%. Patients receiving IV therapies demonstrated a 44% greater average LOS (6.2 hours vs 4.3 hours) and those receiving IV therapies had higher 7-day ED revisit rates (12.0% vs 8.8%) as well as 7-day ED revisits resulting in readmission (2.4% vs 1.0%). 'mso-spacerun:yes'> Secondary outcomes were a comparison of ED LOS, ED revisits at 7 days and ED revisits resulting in admission at 7 days for the IV and non-IV groups. Conclusion: This is the first study to examine physician preference for the use of IV therapies in a low-acuity population and has demonstrated in excess of a 47-fold variation between both extremes of use. Reducing practice variation in this area of ED care by standardizing indications for IV therapies could result in more rational resource utilization and improved throughput.

Early embryo development following fertilization occurs in the oviduct. However, despite being the site of fertilization in cattle, it is possible to by-pass the oviduct by producing embryos in vitro and/or by transferring blastocysts recovered from one female into the uterus of another. While there is substantial evidence for the oviduct having an influence on the quality of the developing embryo, manifested in altered morphology, gene expression and cryotolerance, evidence for a two-way dialogue is weak. In contrast, successful growth and development of the post-hatching blastocyst and pregnancy establishment are a result of the two-way interaction between a competent embryo and a receptive uterine environment. Progesterone (P4) plays a key role in reproductive events associated with establishment and maintenance of pregnancy through its action on the uterine endometrium. Elevated concentrations of circulating P4 in the immediate post-conception period have been associated with an advancement of conceptus elongation, an increase in interferon-tau production and, in some studies, higher pregnancy rates in cattle. This review summarizes current knowledge on the communication between the developing embryo and the maternal reproductive tract.