Local immune recognition of trophoblast in early human pregnancy: controversies and questions.

The role of the maternal immune system in reproductive success in humans remains controversial. Here we focus on the events that occur in the maternal decidua during the first few weeks of human pregnancy, because this is the site at which maternal leukocytes initially interact with and can recognize fetal trophoblast cells, potentially involving allorecognition by both T cells and natural killer (NK) cells. NK cells are the dominant leukocyte population in first-trimester decidua, and genetic studies point to a role of allorecognition by uterine NK cells in establishing a boundary between the mother and the fetus. By contrast, definitive evidence that allorecognition by decidual T cells occurs during the first trimester is lacking. Thus, our view is that during the crucial period when the placenta is established, damaging T cell-mediated adaptive immune responses towards placental trophoblast are minimized, whereas NK cell allorecognition contributes to successful implantation and healthy pregnancy.

Beyond Maternal Tolerance: Education of Uterine Natural Killer Cells by Maternal MHC Drives Fetal Growth.

Reproductive immunology has moved on from the classical Medawar question of 60 years ago "why doesn't the mother reject the fetus?". Looking beyond fetal-maternal tolerance, modern reproductive immunology focuses on how the maternal immune system supports fetal growth. Maternal uterine natural killer (uNK) cells, in partnership with fetal trophoblast cells, regulate physiological vascular changes in the uterus of pregnant women and mice. These vascular changes are necessary to build the placenta and sustain fetal growth. NK cell functions in the uterus and elsewhere, including anti-viral and anti-tumour immunity mediated mostly by blood NK cells, are modulated by NK cell education, a quantifiable process that determines cellular activation thresholds. This process relies largely on interactions between self-MHC class I molecules and inhibitory NK cell receptors. By getting to know self, the maternal immune system sets up uNK cells to participate to tissue homeostasis in the womb. Placentation can be viewed as a form of natural transplantation unique in vertebrates and this raises the question of how uNK cell education or missing-self recognition affect their function and, ultimately fetal growth. Here, using combinations of MHC-sufficient and -deficient mice, we show that uNK cell education is linked to maternal and not fetal MHC, so that MHC-deficient dams produce more growth-restricted fetuses, even when the fetuses themselves express self-MHC. We also show that, while peripheral NK cells reject bone marrow cells according to the established rules of missing-self recognition, uNK cells educated by maternal MHC do not reject fetuses that miss self-MHC and these fetuses grow to their full potential. While these results are not directly applicable to clinical research, they show that NK education by maternal MHC-I is required for optimal fetal growth.

Interventions targeted at women to encourage the uptake of cervical screening.

BACKGROUND: This is an update of the Cochrane review published in Issue 5, 2011. Worldwide, cervical cancer is the fourth commonest cancer affecting women. High-risk human papillomavirus (HPV) infection is causative in 99.7% of cases. Other risk factors include smoking, multiple sexual partners, the presence of other sexually transmitted diseases and immunosuppression. Primary prevention strategies for cervical cancer focus on reducing HPV infection via vaccination and data suggest that this has the potential to prevent nearly 90% of cases in those vaccinated prior to HPV exposure. However, not all countries can afford vaccination programmes and, worryingly, uptake in many countries has been extremely poor. Secondary prevention, through screening programmes, will remain critical to reducing cervical cancer, especially in unvaccinated women or those vaccinated later in adolescence. This includes screening for the detection of pre-cancerous cells, as well as high-risk HPV. In the UK, since the introduction of the Cervical Screening Programme in 1988, the associated mortality rate from cervical cancer has fallen. However, worldwide, there is great variation between countries in both coverage and uptake of screening. In some countries, national screening programmes are available whereas in others, screening is provided on an opportunistic basis. Additionally, there are differences within countries in uptake dependent on ethnic origin, age, education and socioeconomic status. Thus, understanding and incorporating these factors in screening programmes can increase the uptake of screening. This, together with vaccination, can lead to cervical cancer becoming a rare disease. OBJECTIVES: To assess the effectiveness of interventions aimed at women, to increase the uptake, including informed uptake, of cervical screening. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), Issue 6, 2020. MEDLINE, Embase and LILACS databases up to June 2020. We also searched registers of clinical trials, abstracts of scientific meetings, reference lists of included studies and contacted experts in the field. SELECTION CRITERIA: Randomised controlled trials (RCTs) of interventions to increase uptake/informed uptake of cervical screening. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data and assessed risk of bias. Where possible, the data were synthesised in a meta-analysis using standard Cochrane methodology. MAIN RESULTS: Comprehensive literature searches identified 2597 records; of these, 70 met our inclusion criteria, of which 69 trials (257,899 participants) were entered into a meta-analysis. The studies assessed the effectiveness of invitational and educational interventions, lay health worker involvement, counselling and risk factor assessment. Clinical and statistical heterogeneity between trials limited statistical pooling of data. Overall, there was moderate-certainty evidence to suggest that invitations appear to be an effective method of increasing uptake compared to control (risk ratio (RR) 1.71, 95% confidence interval (CI) 1.49 to 1.96; 141,391 participants; 24 studies). Additional analyses, ranging from low to moderate-certainty evidence, suggested that invitations that were personalised, i.e. personal invitation, GP invitation letter or letter with a fixed appointment, appeared to be more successful. More specifically, there was very low-certainty evidence to support the use of GP invitation letters as compared to other authority sources' invitation letters within two RCTs, one RCT assessing 86 participants (RR 1.69 95% CI 0.75 to 3.82) and another, showing a modest benefit, included over 4000 participants (RR 1.13, 95 % CI 1.05 to 1.21). Low-certainty evidence favoured personalised invitations (telephone call, face-to-face or targeted letters) as compared to standard invitation letters (RR 1.32, 95 % CI 1.11 to 1.21; 27,663 participants; 5 studies). There was moderate-certainty evidence to support a letter with a fixed appointment to attend, as compared to a letter with an open invitation to make an appointment (RR 1.61, 95 % CI 1.48 to 1.75; 5742 participants; 5 studies). Low-certainty evidence supported the use of educational materials (RR 1.35, 95% CI 1.18 to 1.54; 63,415 participants; 13 studies) and lay health worker involvement (RR 2.30, 95% CI 1.44 to 3.65; 4330 participants; 11 studies). Other less widely reported interventions included counselling, risk factor assessment, access to a health promotion nurse, photo comic book, intensive recruitment and message framing. It was difficult to deduce any meaningful conclusions from these interventions due to sparse data and low-certainty evidence. However, having access to a health promotion nurse and attempts at intensive recruitment may have increased uptake. One trial reported an economic outcome and randomised 3124 participants within a national screening programme to either receive the standard screening invitation, which would incur a fee, or an invitation offering screening free of charge. No difference in the uptake at 90 days was found (574/1562 intervention versus 612/1562 control, (RR 0.94, 95% CI: 0.86 to 1.03). The use of HPV self-testing as an alternative to conventional screening may also be effective at increasing uptake and this will be covered in a subsequent review. Secondary outcomes, including cost data, were incompletely documented. The majority of cluster-RCTs did not account for clustering or adequately report the number of clusters in the trial in order to estimate the design effect, so we did not selectively adjust the trials. It is unlikely that reporting of these trials would impact the overall conclusions and robustness of the results. Of the meta-analyses that could be performed, there was considerable statistical heterogeneity, and this should be borne in mind when interpreting these findings. Given this and the low to moderate evidence, further research may change these findings. The risk of bias in the majority of trials was unclear, and a number of trials suffered from methodological problems and inadequate reporting. We downgraded the certainty of evidence because of an unclear or high risk of bias with regards to allocation concealment, blinding, incomplete outcome data and other biases. AUTHORS' CONCLUSIONS: There is moderate-certainty evidence to support the use of invitation letters to increase the uptake of cervical screening. Low-certainty evidence showed lay health worker involvement amongst ethnic minority populations may increase screening coverage, and there was also support for educational interventions, but it is unclear what format is most effective. The majority of the studies were from developed countries and so the relevance of low- and middle-income countries (LMICs), is unclear. Overall, the low-certainty evidence that was identified makes it difficult to infer as to which interventions were best, with exception of invitational interventions, where there appeared to be more reliable evidence.

The CD94/NKG2A inhibitory receptor educates uterine NK cells to optimize pregnancy outcomes in humans and mice.

The conserved CD94/NKG2A inhibitory receptor is expressed by nearly all human and ∼50% of mouse uterine natural killer (uNK) cells. Binding human HLA-E and mouse Qa-1, NKG2A drives NK cell education, a process of unknown physiological importance influenced by HLA-B alleles. Here, we show that NKG2A genetic ablation in dams mated with wild-type males caused suboptimal maternal vascular responses in pregnancy, accompanied by perturbed placental gene expression, reduced fetal weight, greater rates of smaller fetuses with asymmetric growth, and abnormal brain development. These are features of the human syndrome pre-eclampsia. In a genome-wide association study of 7,219 pre-eclampsia cases, we found a 7% greater relative risk associated with the maternal HLA-B allele that does not favor NKG2A education. These results show that the maternal HLA-B→HLA-E→NKG2A pathway contributes to healthy pregnancy and may have repercussions on offspring health, thus establishing the physiological relevance for NK cell education. VIDEO ABSTRACT.

Universal third-trimester ultrasonic screening using fetal macrosomia in the prediction of adverse perinatal outcome: A systematic review and meta-analysis of diagnostic test accuracy.

BACKGROUND: The effectiveness of screening for macrosomia is not well established. One of the critical elements of an effective screening program is the diagnostic accuracy of a test at predicting the condition. The objective of this study is to investigate the diagnostic effectiveness of universal ultrasonic fetal biometry in predicting the delivery of a macrosomic infant, shoulder dystocia, and associated neonatal morbidity in low- and mixed-risk populations. METHODS AND FINDINGS: We conducted a predefined literature search in Medline, Excerpta Medica database (EMBASE), the Cochrane library and ClinicalTrials.gov from inception to May 2020. No language restrictions were applied. We included studies where the ultrasound was performed as part of universal screening and those that included low- and mixed-risk pregnancies and excluded studies confined to high risk pregnancies. We used the estimated fetal weight (EFW) (multiple formulas and thresholds) and the abdominal circumference (AC) to define suspected large for gestational age (LGA). Adverse perinatal outcomes included macrosomia (multiple thresholds), shoulder dystocia, and other markers of neonatal morbidity. The risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Meta-analysis was carried out using the hierarchical summary receiver operating characteristic (ROC) and the bivariate logit-normal (Reitsma) models. We identified 41 studies that met our inclusion criteria involving 112,034 patients in total. These included 11 prospective cohort studies (N = 9986), one randomized controlled trial (RCT) (N = 367), and 29 retrospective cohort studies (N = 101,681). The quality of the studies was variable, and only three studies blinded the ultrasound findings to the clinicians. Both EFW >4,000 g (or 90th centile for the gestational age) and AC >36 cm (or 90th centile) had >50% sensitivity for predicting macrosomia (birthweight above 4,000 g or 90th centile) at birth with positive likelihood ratios (LRs) of 8.74 (95% confidence interval [CI] 6.84-11.17) and 7.56 (95% CI 5.85-9.77), respectively. There was significant heterogeneity at predicting macrosomia, which could reflect the different study designs, the characteristics of the included populations, and differences in the formulas used. An EFW >4,000 g (or 90th centile) had 22% sensitivity at predicting shoulder dystocia with a positive likelihood ratio of 2.12 (95% CI 1.34-3.35). There was insufficient data to analyze other markers of neonatal morbidity. CONCLUSIONS: In this study, we found that suspected LGA is strongly predictive of the risk of delivering a large infant in low- and mixed-risk populations. However, it is only weakly (albeit statistically significantly) predictive of the risk of shoulder dystocia. There was insufficient data to analyze other markers of neonatal morbidity.

Distinctive phenotypes and functions of innate lymphoid cells in human decidua during early pregnancy.

During early pregnancy, decidual innate lymphoid cells (dILCs) interact with surrounding maternal cells and invading fetal extravillous trophoblasts (EVT). Here, using mass cytometry, we characterise five main dILC subsets: decidual NK cells (dNK)1-3, ILC3s and proliferating NK cells. Following stimulation, dNK2 and dNK3 produce more chemokines than dNK1 including XCL1 which can act on both maternal dendritic cells and fetal EVT. In contrast, dNK1 express receptors including Killer-cell Immunoglobulin-like Receptors (KIR), indicating they respond to HLA class I ligands on EVT. Decidual NK have distinctive organisation and content of granules compared with peripheral blood NK cells. Acquisition of KIR correlates with higher granzyme B levels and increased chemokine production in response to KIR activation, suggesting a link between increased granule content and dNK1 responsiveness. Our analysis shows that dILCs are unique and provide specialised functions dedicated to achieving placental development and successful reproduction.

In vitro fertilization add-ons for the endometrium: it doesn't add-up.

The probability of live birth from an in vitro fertilization (IVF) cycle is modest. Many additional treatments (add-ons) are available which promise to improve the success of IVF. This review summarizes the current evidence for common IVF add-ons which are suggested to improve endometrial receptivity. Systematic reviews of randomized controlled trials and individual trials were included. Five add-ons were included: immune therapies, endometrial scratching, endometrial receptivity array, uterine artery vasodilation, and human chorionic gonadotropin instillation. The results suggest there is no robust evidence that these add-ons are effective or safe. Many IVF add-ons are costly, consuming precious resources which may be better spent on evidence-based treatments or further IVF. Large randomized controlled trials and appropriate safety assessment should be mandatory before the introduction of IVF add-ons into routine practice.

Changes in thromboelastography parameters in pregnancy, labor, and the immediate postpartum period.

OBJECTIVE: To demonstrate changes in clot mechanics during pregnancy, and to determine the effect that delivery has on immediate postpartum thromboelastography parameters. METHODS: In an observational cross-sectional/longitudinal study, thromboelastography was performed on whole blood aliquots obtained from women carrying singleton pregnancies attending a center in London, UK, between December 2013 and March 2014. Thromboelastography was repeated 6hours after delivery among patients recruited in the third trimester or labor. Bleeding questionnaires were completed and routine clinical/demographic data obtained. RESULTS: Overall, 112 women were included. The thromboelastography parameters were significantly correlated with length of pregnancy. From the third trimester to the postpartum period, there was a significant decrease in time until fibrin formation (R value; 5.8 vs 5.0minutes, P=0.036) and in time to reach a certain clot strength (amplitude of 20mm; K value; 1.3 vs 1.1minutes, P=0.007). From established labor to after delivery, there was a significant increase in clot lysis at 60minutes after the maximum amplitude of clot formation (LY60; 1.8% vs 3.1%, P=0.001). CONCLUSION: The present study describes a novel finding regarding changes in clot mechanics in late pregnancy/puerperium and supports the concept of using thromboelastography as part of the routine assessments at delivery.

First do no harm: uterine natural killer (NK) cells in assisted reproduction.

Natural killer (NK) cells are a type of lymphocyte circulating in peripheral blood named because of their effector functions in killing target cells. Immune cells that share similar phenotypic characteristics but are poor killers populate the uterine lining at implantation and during early pregnancy when the placenta is established. The functions of these uterine NK (uNK) cells are essentially unknown but available data point to a role in regulating placentation in concert with other elements of the decidua and invading trophoblast cells. Despite the lack of scientific rationale and advice from clinical governing bodies, such as the Human Fertilisation and Embryology Authority, an increasing range of tests and therapies are still offered to women undergoing IVF or attending recurrent miscarriage clinics based on the myth that uterine NK cells need suppressing to prevent damage to the embryo. New treatments can be introduced at whim with subsequent demands for expensive trials to prove/disprove their efficacy. The evidence that targeting uNK or peripheral blood NK cells assists women with recurrent pregnancy failure is lacking. Healthcare professionals and patients should very carefully evaluate the practice of immunomodulation to enhance pregnancy outcome. A discussion on how to move towards stricter regulation of immunotherapy in non-hospital settings is now needed because it is clear that the potential risks and costs of these therapies outweigh any benefits.

Service improvement system to enhance the safety of patients admitted on long-term warfarin.

It is common for hospital inpatients on warfarin to suffer from fluctuations in their INR (international normalised ratio). Raised INRs are potentially very dangerous and may result in acute life-threatening haemorrhages. Conversely, low INRs may increase the risk for the development of venous thromboembolism. Having observed many deranged INRs among hospital inpatients, we decided to focus our project on identifying the contributing factors to deranged INRs and ways to address this problem. We analysed the warfarin prescriptions on all drug charts and surveyed the junior doctor staff. Our results revealed poor knowledge and confidence levels on warfarin prescribing among junior doctor staff. This is likely to be reflected in the poor completion rate of warfarin prescriptions. We instituted practical changes to resolve the issue: most importantly, a change to the warfarin administration time from 6 pm to 2 pm, supported by a poster campaign to increase awareness of the problem. The objective of these changes was to reduce prescribing errors by reducing warfarin prescriptions out-of-hours, by the on-call doctors. We repeated the audit cycle twice. Although our interventions were successfully introduced as shown in our second audit cycle, the changes that were implemented were not sustained as shown in the third audit cycle. We identified a need for annual intervention to educate new junior doctor staff to ensure that the positive outcomes achieved are maintained in the long term.