Aspirin for preeclampsia prevention in low- and middle-income countries: mind the gaps.

Preeclampsia is a syndrome that continues to be a major contributor to maternal and neonatal mortality, especially in low-income countries. Low-dose aspirin reduces the risk of preeclampsia, but the mechanism is still unknown. Risk factors to identify women at risk of preeclampsia are based on clinical characteristics. Women identified as high-risk would benefit from aspirin treatment initiated, preferably at the end of the first trimester. Current efforts have largely focused on developing screening algorithms that incorporate clinical risk factors, maternal biomarkers, and uterine artery Doppler evaluated in the first trimester. However, most studies on preeclampsia are conducted in high-income settings, raising uncertainties about whether the information gained can be totally applied in low-resource settings. In low- and middle-income countries, lack of adequate antenatal care and late commencement of antenatal care visits pose significant challenges for both screening for preeclampsia and initiating aspirin treatment. Furthermore, the preventive effect of first-trimester screening based on algorithms and subsequent aspirin treatment is primarily seen for preterm preeclampsia, and reviews indicate minimal or no impact on reducing the risk of term preeclampsia. The lack of evidence regarding the effectiveness of aspirin in preventing term preeclampsia is a crucial concern, as 75% of women will develop this subtype of the syndrome. Regarding adverse outcomes, low-dose aspirin has been linked to a possible higher risk of postpartum hemorrhage, a condition as deadly as preeclampsia in many low- and middle-income countries. The increased risk of postpartum hemorrhage among women in low-income settings should be taken into consideration when discussing which pregnant women would benefit from the use of aspirin and the ideal aspirin dosage for preventing preeclampsia. In addition, women's adherence to aspirin during pregnancy is crucial for determining its effectiveness and complications, an aspect often overlooked in trials. In this review, we analyze the knowledge gaps that must be addressed to safely increase low-dose aspirin use in low- and middle-income countries, and we propose directions for future research.

Preeclampsia epidemiology(ies) and pathophysiology(ies).

Preeclampsia/eclampsia was first described 2000 years ago. Concepts guiding diagnosis have changed over time making longitudinal studies challenging. Similarly, concepts of pathophysiology have evolved from eclampsia as a pregnancy seizure disorder to preeclampsia as a hypertensive and renal disorder to our current concept of a preeclampsia as a pregnancy specific, multisystemic inflammatory disorder. Although preeclampsia is pregnancy specific and many pathophysiologic findings begin to resolve with delivery, its impact extends beyond pregnancy. The risk of cardiovascular and neurological disease is increased after pregnancy in women who have had preeclampsia. The disorder is not a disease, but a syndrome and emerging data indicate multiple pathways to the syndrome. It is likely that our failure to have a major impact on prediction and prevention despite a large increase in understanding is due to the existence of multiple subtypes of preeclampsia. This concept should guide future research.

Inflammatory markers are elevated in early pregnancy, but not late pregnancy, in women with overweight and obesity that later develop preeclampsia.

PROBLEM: Obesity and preeclampsia both involve a pathological inflammatory response, which may be how obesity increases preeclampsia risk. Previous studies have failed to assess robust measurements of inflammatory markers across gestation, specifically in overweight/ obese women in the context of preeclampsia. METHOD OF STUDY: We measured 20 inflammatory markers in plasma via multiplex assay (ThermoFisher Inflammation 20 plex Human ProcartaPlex Panel) across the three trimesters of pregnancy in an existing cohort of overweight and obese women who developed preeclampsia (n = 37) and without preeclampsia (n = 74). Mann-Whitney U tests examined differences in inflammatory marker concentrations between cases and controls. Repeated measures ANOVA tests were used to explore differences in inflammatory marker concentrations over time within cases and controls. RESULTS: Pro-inflammatory markers (IL-1α, IL-1ß, IL-6, IFN-α, IFN-γ, GM-CSF, IL-12p70, IL-17α, TNF-α, IL-8) and anti-inflammatory markers (IL-4, IL-10, IL-13) were higher in the first and second trimester in participants who later developed preeclampsia compared to those who did not (p < .05). Only TNF-α and IL-8 remained elevated in the third trimester. Inflammatory markers did not change across pregnancy in preeclampsia cases but did increase across pregnancy in controls. CONCLUSION: Our findings diverge from prior studies, predominantly of non-obese women, that report lower circulating concentrations of anti-inflammatory cytokines in preeclampsia versus normotensive pregnancy, particularly by late pregnancy. We posit that women with overweight and obesity who develop preeclampsia entered pregnancy with a heightened pro-inflammatory state likely related to obesity, which increased risk for preeclampsia. Further studies are needed to investigate if inflammatory maker profiles differ between obese and non-obese women.

Early Pregnancy Systolic Blood Pressure Patterns Predict Early- and Later-Onset Preeclampsia and Gestational Hypertension Among Ostensibly Low-to-Moderate Risk Groups.

Background Clinical risk factors, a single blood pressure (BP) measurement, current biomarkers, and biophysical parameters can effectively identify risk of early-onset preeclampsia but have limited ability to predict later-onset preeclampsia and gestational hypertension. Clinical BP patterns hold promise to improve early risk stratification for hypertensive disorders of pregnancy. Methods and Results After excluding preexisting hypertension, heart, kidney, or liver disease, or prior preeclampsia, the retrospective cohort (n=249 892) all had systolic BP <140 mm Hg and diastolic BP <90 mm Hg or a single BP elevation ≤20 weeks' gestation, prenatal care at <14 weeks' gestation, and a still or live birth delivery at Kaiser Permanente Northern California hospitals (2009-2019). The sample was randomly split into development (N=174 925; 70%) and validation (n=74 967; 30%) data sets. Predictive performance of multinomial logistic regression models for early-onset (<34 weeks) preeclampsia, later-onset (≥34 weeks) preeclampsia, and gestational hypertension was evaluated in the validation data set. There were 1008 (0.4%), 10 766 (4.3%), and 11 514 (4.6%) patients with early-onset preeclampsia, later-onset preeclampsia, and gestation hypertension, respectively. Models with 6 systolic BP trajectory groups (0-20 weeks' gestation) plus standard clinical risk factors performed substantially better than risk factors alone to predict early- and later-onset preeclampsia and gestational hypertension, with C-statistics (95% CIs) of 0.747 (0.720-0.775), 0.730 (0.722-0.739), and 0.768 (0.761-0.776) versus 0.688 (0.659-0.717), 0.695 (0.686-0.704) and 0.692 (0.683-0.701), respectively, with excellent calibration (Hosmer-Lemeshow P=0.99, 0.99, and 0.74, respectively). Conclusions Early pregnancy BP patterns up to 20 weeks' gestation plus clinical, social, and behavioral factors more accurately discriminate hypertensive disorders of pregnancy risk among low-to-moderate risk pregnancies. Early pregnancy BP trajectories improve risk stratification to reveal higher-risk individuals hidden within ostensibly low-to-moderate risk groups and lower-risk individuals considered at higher risk by US Preventive Services Task Force criteria.

PREPARE: A Stepped-Wedge Cluster-Randomized Trial to Evaluate Whether Risk Stratification Can Reduce Preterm Deliveries Among Patients With Suspected or Confirmed Preterm Preeclampsia.

BACKGROUND: Early delivery in preterm preeclampsia may reduce the risks for the patient, but consequences of prematurity may be substantial for the baby. This trial evaluated whether the implementation of a risk stratification model could safely reduce prematurity. METHODS: This was a stepped-wedge cluster-randomized trial in seven clusters. Patients presenting with suspected or confirmed preeclampsia between 20+0 and 36+6 gestational weeks were considered eligible. At the start of the trial, all centers were allocated in the preintervention phase, and patients enrolled in this phase were managed according to local treatment guidance. Subsequently, every 4 months, 1 randomly allocated cluster transitioned to the intervention. Patients enrolled in the intervention phase had sFlt-1 (soluble fms-like tyrosine kinase-1)/PlGF (placental growth factor) ratio and preeclampsia integrated estimate of risk assessments performed. If sFlt-1/PlGF ≤38 and preeclampsia integrated estimate of risk <10%, patients were considered low risk and clinicians received recommendations to defer delivery. If sFlt-1/PlGF >38 and preeclampsia integrated estimate of risk ≥10%, patients were considered not low risk, and clinicians received recommendations to increase surveillance. The primary outcome was the proportion of patients with preterm preeclampsia delivered prematurely out of total deliveries. RESULTS: Between March 25, 2017 and December 24, 2019, 586 and 563 patients were analyzed in the intervention and usual care groups, respectively. The event rate was 1.09% in the intervention group, and 1.37% in the usual care group. After prespecified adjustments for variation between and within clusters over time, the adjusted risk ratio was 1.45 ([95% CI, 1.04-2.02]; P=0.029), indicating a higher risk of preterm deliveries in the intervention group. Post hoc analysis including calculation of risk differences did not show evidence of statistical differences. Abnormal sFlt-1/PlGF was associated with a higher rate of identifying preeclampsia with severe features. CONCLUSIONS: The introduction of an intervention based on biomarkers and clinical factors for risk stratification did not lead to reductions in preterm deliveries. Further training on the interpretation of disease severity in preeclampsia and the development of additional risk stratification is needed before adoption into clinical practice. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT03073317.

Is the Association Between Fruits and Vegetables and Preeclampsia Due to Higher Dietary Vitamin C and Carotenoid Intakes?

BACKGROUND: Diets dense in fruits and vegetables are associated with a reduced risk of preeclampsia, but pathways underlying this relationship are unclear. Dietary antioxidants may contribute to the protective effect. OBJECTIVE: We determined the extent to which the effect of dietary fruit and vegetable density on preeclampsia is because of high intakes of dietary vitamin C and carotenoids. METHODS: We used data from 7572 participants in the Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be (8 United States medical centers, 2010‒2013). Usual daily periconceptional intake of total fruits and total vegetables was estimated from a food frequency questionnaire. We estimated the indirect effect of ≥2.5 cups/1000 kcal of fruits and vegetables through vitamin C and carotenoid on the risk of preeclampsia. We estimated these effects using targeted maximum likelihood estimation and an ensemble of machine learning algorithms, adjusting for confounders, including other dietary components, health behaviors, and psychological, neighborhood, and sociodemographic factors. RESULTS: Participants who consumed ≥2.5 cups of fruits and vegetables per 1000 kcal were less likely than those who consumed <2.5 cups/1000 kcal to develop preeclampsia (6.4% compared with 8.6%). After confounder adjustment, we observed that higher fruit and vegetable density was associated with 2 fewer cases of preeclampsia (risk difference: -2.0; 95% CI: -3.9, -0.1)/100 pregnancies compared with lower density diets. High dietary vitamin C and carotenoid intake was not associated with preeclampsia. The protective effect of high fruit and vegetable density on the risk of preeclampsia and late-onset preeclampsia was not mediated through dietary vitamin C and carotenoids. CONCLUSIONS: Evaluating other nutrients and bioactives in fruits and vegetables and their synergy is worthwhile, along with characterizing the effect of individual fruits or vegetables on preeclampsia risk.

Prepregnancy obesity and risk of placental inflammation at term: a selection bias analysis.

PURPOSE: Placental histopathology is a resource for investigating obesity-associated pregnancy conditions. However, studies oversample adverse pregnancies, biasing findings. We examine the association between prepregnancy obesity (risk factor for inflammation) and histologic placental inflammation (correlated with impaired infant neurodevelopment) and how selection bias may influence the association. METHODS: Singleton term deliveries between 2008 and 2012 from the Magee Obstetric Maternal and Infant database were analyzed. Prepregnancy body mass index (BMI) was categorized as underweight, lean (referent), overweight, and obese. Outcomes were diagnoses of acute (acute chorioamnionitis and fetal inflammation) and chronic placental inflammation (chronic villitis). Risk ratios for associations between BMI and placental inflammation were estimated using selection bias approaches: complete case, exclusion of pregnancy complications, multiple imputation, and inverse probability weighting. E-values approximated how susceptible estimates were to residual selection bias. RESULTS: Across methods, obesity was associated with an 8-15% lower risk of acute chorioamnionitis, a 7%-14% lower risk of acute fetal inflammation, and a 12%-30% higher risk of chronic villitis relative to lean women. E-values indicated modest residual selection bias could explain away associations, though few measured indications of placental evaluations met this threshold. CONCLUSIONS: Obesity may contribute to placental inflammation, and we highlight robust methods to analyze clinical data susceptible to selection bias.

A longitudinal epigenome-wide association study of preeclamptic and normotensive pregnancy.

Background: While preeclampsia (PE) is a leading cause of pregnancy-related morbidity/mortality, its underlying mechanisms are not fully understood. DNA methylation (DNAm) is a dynamic regulator of gene expression that may offer insight into PE pathophysiology and/or serve as a biomarker (e.g., risk, subtype, a therapeutic response). This study's purpose was to evaluate for differences in blood-based DNAm across all trimesters between individuals eventually diagnosed with PE (cases) and individuals who remained normotensive throughout pregnancy, did not develop proteinuria, and birthed a normally grown infant (controls). Results: In the discovery phase, longitudinal, genome-wide DNAm data were generated across three trimesters of pregnancy in 56 participants (n=28 cases, n=28 controls) individually matched on self-identified race, pre-pregnancy body mass index, smoking, and gestational age at sample collection. An epigenome-wide association study (EWAS) was conducted, using surrogate variable analysis to account for unwanted sources of variation. No CpGs met the genome-wide significance p value threshold of 9×10-8, but 16 CpGs (trimester 1: 5; trimester 2: 1; trimester 3: 10) met the suggestive significance threshold of 1×10-5. DNAm data were also evaluated for differentially methylated regions (DMRs) by PE status. Three DMRs in each trimester were significant after Bonferonni-adjustment. Since only third-trimester samples were available from an independent replication sample (n=64 cases, n=50 controls), the top suggestive hits from trimester 3 (cg16155413 and cg21882990 associated with TRAF3IP2-AS1/TRAF3IP2 genes, which also made up the top DMR) were carried forward for replication. During replication, DNAm data were also generated for validation purposes from discovery phase third trimester samples. While significant associations between DNAm and PE status were observed at both sites in the validation sample, no associations between DNAm and PE status were observed in the independent replication sample. Conclusions: The discovery phase findings for cg16155413/cg21882990 (TRAF3IP2-AS1/TRAF3IP2) were validated with a new platform but were not replicated in an independent sample. Given the differences in participant characteristics between the discovery and replication samples, we cannot rule out important signals for these CpGs. Additional research is warranted for cg16155413/cg21882990, as well as top hits in trimesters 1-2 and significant DMRs that were not examined in the replication phase.

Lipidomics Reveals Elevated Plasmalogens in Women with Obesity Who Develop Preeclampsia.

Objective: Preeclampsia (PE) is a prevalent pregnancy disorder worldwide with limited preventative treatments available. Obesity triples the risk for PE, yet only 10% of women with obesity develop PE. The factors that distinguish PE from uncomplicated pregnancies in the context of obesity have not been fully established. Methods: We studied a cohort of women with obesity throughout pregnancy to identify lipid mediators and/or biomarkers of PE. Blood samples were collected at each trimester and analyzed by both targeted lipidomics and standard lipid panels. Individual lipid species were compared by PE status at each trimester, as well as by self-identified race (Black vs. White) and fetal sex. Results: Standard lipid panels and clinical measurements revealed few differences between PE and uncomplicated pregnancies. Targeted lipidomics, however, identified plasmalogen, phosphatidylethanolamine, and free fatty acid species that were elevated in the third trimester of women with PE. Furthermore, race and trimester of pregnancy were considerable sources of plasma lipidomic variation in women with obesity. Conclusions: First and second trimester individual plasma lipid species do not predict the development of PE in obese women. In the third trimester, PE patients have elevated levels of plasmalogens-a class of lipoprotein-associated phospholipids that have been implicated in the response to oxidative stress.

Care plan for individuals at risk for preeclampsia: shared approach to education, strategies for prevention, surveillance, and follow-up.

Preeclampsia is a multisystemic disorder of pregnancy that affects 250,000 pregnant individuals in the United States and approximately 10 million worldwide per annum. Preeclampsia is associated with substantial immediate morbidity and mortality but also long-term morbidity for both mother and offspring. It is now clearly established that a low dose of aspirin given daily, beginning early in pregnancy modestly reduces the occurrence of preeclampsia. Low-dose aspirin seems safe, but because there is a paucity of information about long-term effects on the infant, it is not recommended for all pregnant individuals. Thus, several expert groups have identified clinical factors that indicate sufficient risk to recommend low-dose aspirin preventive therapy. These risk factors may be complemented by biochemical and/or biophysical tests that either indicate increased probability of preeclampsia in individuals with clinical risk factors, or more importantly, identify increased likelihood in those without other evident risk. In addition, the opportunity exists to provide this population with additional care that may prevent or mitigate the short- and long-term effects of preeclampsia. Patient and provider education, increased surveillance, behavioral modification, and other approaches to improve outcomes in these individuals can improve the chance of a healthy outcome. We assembled a group with diverse, relevant expertise (clinicians, investigators, advocates, and public and private stakeholders) to develop a care plan in which providers and pregnant individuals at risk can work together to reduce the risk of preeclampsia and associated morbidities. The plan is for care of individuals at moderate to high risk for developing preeclampsia, sufficient to receive low-dose aspirin therapy, as identified by clinical and/or laboratory findings. The recommendations are presented using the GRADE methodology with the quality of evidence upon which each is based. In addition, printable appendices with concise summaries of the care plan's recommendations for patients and healthcare providers are provided. We believe that this shared approach to care will facilitate prevention of preeclampsia and its attendant short- and long-term morbidity in patients identified as at risk for development of this disorder.

Elevated levels of chloramines and chlorine detected near an indoor sports complex.

Chloramines (NH2Cl, NHCl2, and NCl3) are toxic compounds that can be created during the use of bleach-based disinfectants that contain hypochlorous acid (HOCl) and the hypochlorite ion (OCl-) as their active ingredients. Chloramines can then readily transfer from the aqueous-phase to the gas-phase. Atmospheric chemical ionization mass spectrometry using iodide adduct chemistry (I-CIMS) made observations across two periods (2014 and 2016) at an urban background site on the University of Leicester campus (Leicester, UK). Both monochloramine (NH2Cl) and molecular chlorine (Cl2) were detected and positively identified from calibrated mass spectra during both sampling periods and to our knowledge, this is the first detection of NH2Cl outdoors. Mixing ratios of NH2Cl reached up to 2.2 and 4.0 parts per billion by volume (ppbv), with median mixing ratios of 30 and 120 parts per trillion by volume (pptv) during the 2014 and 2016 sampling periods, respectively. Levels of Cl2 were observed to reach up to 220 and 320 pptv. Analysis of the NH2Cl and Cl2 data pointed to the same local source, a nearby indoor sports complex with a swimming pool and a cleaning product storage shed. No appreciable levels of NHCl2 and NCl3 were observed outdoors, suggesting the indoor pool was not likely to be the primary source of the observed ambient chloramines, as prior measurements made in indoor pool atmospheres indicate that NCl3 would be expected to dominate. Instead, these observations point to indoor cleaning and/or cleaning product emissions as the probable source of NH2Cl and Cl2 where the measured levels provide indirect evidence for substantial amounts transported from indoors to outdoors. Our upper estimate for total NH2Cl emissions from the University of Leicester indoor sports complexes scaled for similar sports complexes across the UK is 3.4 × 105 ± 1.1 × 105 µg h-1 and 0.0017 ± 0.00034 Gg yr-1, respectively. The Cl-equivalent emissions in HCl are only an order of magnitude less to those from hazardous waste incineration and iron and steel sinter production in the UK National Atmospheric Emissions Inventory (NAEI).

Recruiting and retaining nulliparous individuals with a family history of hypertensive disorders of pregnancy to participate in scientific research prior to pregnancy: The Sisterhood Study.

Introduction: Recruiting women with a family history (FH) of hypertensive disorders of pregnancy (HDP) to participate in research before pregnancy could offer insight into genetic and lifestyle factors that incur higher risk of cardiovascular disease during pregnancy and throughout the life course. Methods: The Sisterhood Study piloted low-touch, remote recruitment strategies that relied on women with a history of preeclampsia to share study information with family and friends. It aimed to enroll 150 women with a FH of HDP and 150 controls. Results: The study recruited 328 women (104 with a FH of HDP, 131 without a FH, and 93 with unknown FH) prior to pregnancy. The majority identified as non-Hispanic White (74.7%) and had > high school education (91.8%). Discussion: Although the population was enriched with nulliparous women with a FH of HDP, it was not sufficient to recruit a diverse cohort large enough to meet the study aim.

Characterization of placental and decidual cell development in early pregnancy loss by single-cell RNA sequencing.

BACKGROUND: Early pregnancy loss (EPL) presents as sporadic or recurrent miscarriage during the first trimester. In addition to chromosomal defects, EPL may result from impairment of the placental-decidual interface at early gestational age due to gene-environmental interactions. METHODS: To better understand the pathogenesis associated with this impairment, cell development in chorionic villi and decidua of different forms of EPL (sporadic or recurrent) was investigated with single-cell RNA sequencing and compared to that of normal first-trimester tissue. RESULTS: Unique gene expression signatures were obtained for the different forms of EPL and for normal tissue and the composition of placental and decidual cell clusters in each form was established. In particular, the involvement of macrophages in the EPL phenotypes was identified revealing an immunoactive state. CONCLUSION: Differential gene expression and unique marker genes among cell clusters from chorionic villi and decidua of miscarried and normal pregnancies, may lead to identification of biomarker for EPL.

The Global Pregnancy Collaboration (CoLab) symposium on short- and long-term outcomes in offspring whose mothers had preeclampsia: A scoping review of clinical evidence.

Preeclampsia is a maternal syndrome characterized by the new onset of hypertension after 20 weeks of gestation associated with multisystemic complications leading to high maternal and fetal/neonatal morbidity and mortality. However, sequelae of preeclampsia may extend years after pregnancy in both mothers and their children. In addition to the long-term adverse cardiovascular effects of preeclampsia in the mother, observational studies have reported elevated risk of cardiovascular, metabolic, cerebral and cognitive complications in children born from women with preeclampsia. Less clear is whether the association between maternal preeclampsia and offspring sequelae are causal, or to what degree the associations might be driven by fetal factors including impaired growth and the health of its placenta. Our discussion of these complexities in the 2018 Global Pregnancy Collaboration annual meeting prompted us to write this review. We aimed to summarize the evidence of an association between maternal preeclampsia and neurobehavioral developmental disorders in offspring in hopes of generating greater research interest in this important topic.

Evaluation of a protein-to-creatinine dipstick diagnostic test for proteinuria screening in selected antenatal care clinics in three Districts in the Bono-East Region of Ghana.

BACKGROUND: Preeclampsia and eclampsia contribute significantly to maternal and newborn deaths worldwide. Early and accurate identification of pregnant women at risk can avert these deaths, but the necessary diagnostics are not widely available. A protein and creatinine ratio, rather than a measurement of protein alone, may provide better identification of proteinuria. The objective of this study was to assess the operational and performance characteristics of the LifeAssay Diagnostics (LAD) Test-it™ protein-to-creatinine ratio (PrCr) urinalysis dipstick test in a representative antenatal care setting (ANC). METHODS: Mixed methods were used to assess the operational and performance characteristics of the PrCr test, including a usability study with 25 participants, a prospective cross-sectional diagnostic accuracy study (N = 1483), and a targeted reassessment of discordant frozen samples (N = 200). Several other commonly used proteinuria tests were included for comparison. RESULTS: The test demonstrated improved clinical performance for detection of proteinuria over the current standard-of-care tests widely used in Ghana. The LAD PrCr test showed a sensitivity of 50.7% and specificity of 69.2% when run at the point of care. In contrast, the standard-of-care Accu-Tell® protein dipstick test was found to have a sensitivity of 32.4% and a specificity of 82.2%. The LAD test shows minor improvement over the tests currently used in Ghana to detect proteinuria. CONCLUSIONS: The PrCr test offers the potential for improved detection of proteinuria over the standard-of-care tests used in ANC. However, this test and the others evaluated for this study demonstrate limited performance, particularly among samples with a low level of proteinuria. Additional exploration in other clinical use cases, such as triage among high-risk populations, is warranted. The LAD test can also be considered a transition product, as health systems consider adopting next-generation biomarker tests when more readily available.

Vision for Improving Pregnancy Health: Innovation and the Future of Pregnancy Research.

Understanding, predicting, and preventing pregnancy disorders have been a major research target. Nonetheless, the lack of progress is illustrated by research results related to preeclampsia and other hypertensive pregnancy disorders. These remain a major cause of maternal and infant mortality worldwide. There is a general consensus that the rate of progress toward understanding pregnancy disorders lags behind progress in other aspects of human health. In this presentation, we advance an explanation for this failure and suggest solutions. We propose that progress has been impeded by narrowly focused research training and limited imagination and innovation, resulting in the failure to think beyond conventional research approaches and analytical strategies. Investigations have been largely limited to hypothesis-generating approaches constrained by attempts to force poorly defined complex disorders into a single "unifying" hypothesis. Future progress could be accelerated by rethinking this approach. We advise taking advantage of innovative approaches that will generate new research strategies for investigating pregnancy abnormalities. Studies should begin before conception, assessing pregnancy longitudinally, before, during, and after pregnancy. Pregnancy disorders should be defined by pathophysiology rather than phenotype, and state of the art agnostic assessment of data should be adopted to generate new ideas. Taking advantage of new approaches mandates emphasizing innovation, inclusion of large datasets, and use of state of the art experimental and analytical techniques. A revolution in understanding pregnancy-associated disorders will depend on networks of scientists who are driven by an intense biological curiosity, a team spirit, and the tools to make new discoveries.

Hydrogen chloride (HCl) at ground sites during CalNex 2010 and insight into its thermodynamic properties.

Gas phase hydrogen chloride (HCl) was measured at Pasadena and San Joaquin Valley (SJV) ground sites in California during May and June 2010 as part of the CalNex study. Observed mixing ratios were on average 0.83 ppbv at Pasadena, ranging from below detection limit (0.055 ppbv) to 5.95 ppbv, and were on average 0.084 ppbv at SJV with a maximum value of 0.776 ppbv. At both sites, HCl levels were highest during midday and shared similar diurnal variations with HNO3. Coupled phase partitioning behavior was found between HCl/Cl- and HNO3/NO3 - using thermodynamic modelling and observations. Regional modeling of Cl- and HCl using CMAQ captures some of the observed relationships but underestimates measurements by a factor of 5 or more. Chloride in the 2.5-10 µm size range in Pasadena was sometimes higher than sea salt abundances, based on co-measured Na+, implying that sources other than sea salt are important. The acid-displacement of HCl/Cl- by HNO3/NO3 - (phase partitioning of semi-volatile acids) observed at the SJV site can only be explained by aqueous phase reaction despite low RH conditions and suggests the temperature dependence of HCl phase partitioning behavior was strongly impacted by the activity coefficient changes under relevant aerosol conditions (e.g., high ionic strength). Despite the influence from activity coefficients, the gas-particle system was found to be well constrained by other stronger buffers and charge balance so that HCl and Cl- concentrations were reproduced well by thermodynamic models.

Latent class analysis of placental histopathology: a novel approach to classifying early and late preterm births.

BACKGROUND: Neonatal morbidity attributable to prematurity predominantly occurs among early preterm births (<32 weeks) rather than late preterm births (32 to <37 weeks). Methods to distinguish early and late preterm births are lacking given the heterogeneity in pathophysiology and risk factors, including maternal obesity. Although preterm births are often characterized by clinical presentation (spontaneous or clinically indicated), classifying deliveries by placental features detected on histopathology reports may help identify subgroups of preterm births with similar etiology and risk factors. Latent class analysis is an empirical approach to characterize preterm births on the basis of observed combinations of placental features. OBJECTIVE: To identify histopathologic markers that can distinguish early (<32 weeks) and late preterm births (32 to <37 weeks) that are also associated with maternal obesity and neonatal outcomes. STUDY DESIGN: Women with a singleton preterm birth at University of Pittsburgh Medical Center Magee-Womens Hospital (Pittsburgh, PA) from 2008 to 2012 and a placental evaluation (89% of preterm births) were stratified into early (n=900, 61% spontaneous) and late preterm births (n=3362, 57% spontaneous). Prepregnancy body mass index was self-reported at first prenatal visit and 16 abstracted placental features were analyzed. Placental subgroups (ie, latent classes) of early and late preterm births were determined separately by latent class analysis of placental features. The optimal number of latent classes was selected by comparing fit statistics. The probability of latent class membership across prepregnancy body mass indexes was estimated in early preterm births and in late preterm births by an extension of multinomial regression called pseudo-class regression, adjusting for race, smoking, education, and parity. The frequencies of severe neonatal morbidity (composite outcome: respiratory distress, bronchopulmonary dysplasia, intraventricular hemorrhage, necrotizing enterocolitis, periventricular leukomalacia, patent ductus arteriosus, and retinopathy of prematurity), small-for-gestational-age, and length of neonatal intensive care unit stay were compared across latent classes by chi-square and Kruskal-Wallis tests. RESULTS: Early preterm births were grouped into 4 latent classes based on placental histopathologic features: acute inflammation (38% of cases), maternal vascular malperfusion with inflammation (29%), maternal vascular malperfusion (25%), and fetal vascular thrombosis with hemorrhage (8%). As body mass index increased from 20 to 50kg/m2, the probability of maternal vascular malperfusion and fetal vascular thrombosis with hemorrhage increased, whereas the probability of maternal vascular malperfusion with inflammation decreased. There was minimal change in the probability of acute inflammation with increasing body mass index. Late preterm births also had 4 latent classes: maternal vascular malperfusion (22%), acute inflammation (12%), fetal vascular thrombosis with hemorrhage (9%), and low-risk pathology (58%). Body mass index was not associated with major changes in likelihood of the latent classes in late preterm births. Associations between body mass index and likelihood of the latent classes were not modified by type of delivery (spontaneous or indicated) in early or late preterm births. Maternal malperfusion and fetal vascular thrombosis with hemorrhage were associated with greater neonatal morbidity than the other latent classes in early and late preterm births. CONCLUSION: Obesity may predispose women to early but not late preterm birth through placental vascular impairment. Latent class analysis of placental histopathologic data provides an evidence-based approach to group preterm births with shared underlying etiology and risk factors.

RNA profiles reveal signatures of future health and disease in pregnancy.

Maternal morbidity and mortality continue to rise, and pre-eclampsia is a major driver of this burden1. Yet the ability to assess underlying pathophysiology before clinical presentation to enable identification of pregnancies at risk remains elusive. Here we demonstrate the ability of plasma cell-free RNA (cfRNA) to reveal patterns of normal pregnancy progression and determine the risk of developing pre-eclampsia months before clinical presentation. Our results centre on comprehensive transcriptome data from eight independent prospectively collected cohorts comprising 1,840 racially diverse pregnancies and retrospective analysis of 2,539 banked plasma samples. The pre-eclampsia data include 524 samples (72 cases and 452 non-cases) from two diverse independent cohorts collected 14.5 weeks (s.d., 4.5 weeks) before delivery. We show that cfRNA signatures from a single blood draw can track pregnancy progression at the placental, maternal and fetal levels and can robustly predict pre-eclampsia, with a sensitivity of 75% and a positive predictive value of 32.3% (s.d., 3%), which is superior to the state-of-the-art method2. cfRNA signatures of normal pregnancy progression and pre-eclampsia are independent of clinical factors, such as maternal age, body mass index and race, which cumulatively account for less than 1% of model variance. Further, the cfRNA signature for pre-eclampsia contains gene features linked to biological processes implicated in the underlying pathophysiology of pre-eclampsia.

Syncytiotrophoblast stress in preeclampsia: the convergence point for multiple pathways.

Preeclampsia evolves in 2 stages: a placental problem that generates signals to the mother to cause a range of responses that comprise the second stage (preeclampsia syndrome). The first stage of early-onset preeclampsia is poor placentation, which we here call malplacentation. The spiral arteries are incompletely remodeled, leading to later placental malperfusion, relatively early in the second half of pregnancy. The long duration of the first stage (several months) is unsurprisingly associated with fetal growth restriction. The first stage of late-onset preeclampsia, approximately 80% of total cases, is shorter (several weeks) and part of a process that is common to all pregnancies. Placental function declines as it outgrows uterine capacity, with increasing chorionic villous packing, compression of the intervillous space, and fetal hypoxia, and causes late-onset clinical presentations such as "unexplained" stillbirths, late-onset fetal growth restriction, or preeclampsia. The second stages of early- and late-onset preeclampsia share syncytiotrophoblast stress as the most relevant feature that causes the maternal syndrome. Syncytiotrophoblast stress signals in the maternal circulation are probably the most specific biomarkers for preeclampsia. In addition, soluble fms-like tyrosine kinase-1 (mainly produced by syncytiotrophoblast) is the best-known biomarker and is routinely used in clinical practice in many locations. How the stress signals change over time in normal pregnancies indicates that syncytiotrophoblast stress begins on average at 30 to 32 weeks' gestation and progresses to term. At term, syncytiotrophoblast shows increasing markers of stress, including apoptosis, pyroptosis, autophagy, syncytial knots, and necrosis. We label this phenotype the "twilight placenta" and argue that it accounts for the clinical problems of postmature pregnancies. Senescence as a stress response differs in multinuclear syncytiotrophoblast from that of mononuclear cells. Syncytiotrophoblast irreversibly acquires part of the senescence phenotype (cell cycle arrest) when it is formed by cell fusion. The 2 pathways converge on the common pathologic endpoint, syncytiotrophoblast stress, and contribute to preeclampsia subtypes. We highlight that the well-known heterogeneity of the preeclampsia syndrome arises from different pathways to this common endpoint, influenced by maternal genetics, epigenetics, lifestyle, and environmental factors with different fetal and maternal responses to the ensuing insults. This complexity mandates a reassessment of our approach to predicting and preventing preeclampsia, and we summarize research priorities to maximize what we can learn about these important issues.