Maternal total cell-free DNA in preeclampsia and fetal growth restriction: Evidence of differences in maternal response to abnormal implantation

Cord Blood Cell-Free DNA Concentration: A Novel Marker for Neonatal Wellbeing

OBJECTIVE

 Cord gas values and Apgar scores, currently used as markers for newborn wellbeing and postpartum complications, provide rough estimates, and their use remains elusive. Circulating cell-free DNA (cfDNA) may better represent newborn status at birth and the effect of parturition on the fetus. This pilot study investigates the association between cord blood (CB) cfDNA and neonatal outcomes.

STUDY DESIGN

 In a prospective cohort study, cfDNA concentration was measured in immediately following delivery collected CB sera of newborns using our rapid fluorescent assay.

RESULTS

 During the study period, blood samples from umbilical cords of 100 newborns were collected. Vaginal delivery was associated with a higher median CB cfDNA than cesarean delivery (277 [95% confidence interval [CI] 199-377] vs. 100 [95% CI 43-265] ng/mL, p < 0.01). cfDNA levels were significantly associated with gestational age at delivery (rho = 0.308, p = 0.002) and CB base deficit (BD, r = 0.252, p = 0.017). According to maternal and fetal complications, CB cfDNA was elevated in fetuses with category II of heart rate tracing (p < 0.05), with maternal positive vaginal culture (p < 0.01), and with premature rupture of membranes (PROM, p < 0.001). Logistic regression models of CB cfDNA fourth quartiles demostrate a double odds ratio for elevated BD (>3mmol/L) and for worse heart rate tracing category.

CONCLUSION

 Serum CB cfDNA concentration reflects the newborn's status and hazards with an excellent association with CB BD, fetal heart rate category, and maternal risk factors for infection (positive vaginal culture and PROM). This preliminary observation suggests that cfDNA can serve as a point of care biomarker for newborn status at the time of delivery.

KEY POINTS

· CB cfDNA levels correlated with newborn's BD.. · CB cfDNA levels reflect parturition stress and inflammation.. · cfDNA serve as a diagnostic and prediction tool for the identification of newborns at risk for morbidity..

A Reliable Method for Quantifying Plasma Cell-Free DNA Using an Internal Standard Strategy: Evaluation in a Cohort of Non-Pregnant and Pregnant Women

The use of plasma cell-free DNA (cfDNA) as a useful biomarker in obstetric clinical practice has been delayed due to the lack of reliable quantification protocols. We developed a protocol to quantify plasma cfDNA using an internal standard strategy to overcome difficulties posed by low levels and high fragmentation of cfDNA. cfDNA was isolated from plasma samples of non-pregnant (NP, n = 26) and pregnant (P, n = 26) women using a commercial kit and several elution volumes were evaluated. qPCR parameters were optimized for cfDNA quantification, and several quantities of a recombinant standard were evaluated as internal standard. Absolute quantification was performed using a standard curve and the quality of the complete method was evaluated. cfDNA was eluted in a 50-μl volume, actin-β (ACTB) was selected as the target gene, and qPCR parameters were optimized. The ACTB standard was constructed and 1000 copies were selected as internal standard. The standard curve showed R2 = 0.993 and E = 109.7%, and the linear dynamic range was defined between 102 and 106 ACTB copies/tube. Repeatability and reproducibility in terms of CV were 19% and up to 49.5% for ACTB copies per milliliter of plasma, respectively. The range of cfDNA levels was 428-18,851 copies/mL in NP women and 4031-2,019,363 copies/mL in P women, showing significant differences between the groups. We recommend the application of internal standard strategy for a reliable plasma cfDNA quantification. This methodology holds great potential for a future application in the obstetric field.

Predicting the onset of preeclampsia by longitudinal monitoring of metabolic changes throughout pregnancy with Raman spectroscopy

Preeclampsia is a life-threatening pregnancy disorder. Current clinical assays cannot predict the onset of preeclampsia until the late 2nd trimester, which often leads to poor maternal and neonatal outcomes. Here we show that Raman spectroscopy combined with machine learning in pregnant patient plasma enables rapid, highly sensitive maternal metabolome screening that predicts preeclampsia as early as the 1st trimester with >82% accuracy. We identified 12, 15 and 17 statistically significant metabolites in the 1st, 2nd and 3rd trimesters, respectively. Metabolic pathway analysis shows multiple pathways corresponding to amino acids, fatty acids, retinol, and sugars are enriched in the preeclamptic cohort relative to a healthy pregnancy. Leveraging Pearson's correlation analysis, we show for the first time with Raman Spectroscopy that metabolites are associated with several clinical factors, including patients' body mass index, gestational age at delivery, history of preeclampsia, and severity of preeclampsia. We also show that protein quantification alone of proinflammatory cytokines and clinically relevant angiogenic markers are inadequate in identifying at-risk patients. Our findings demonstrate that Raman spectroscopy is a powerful tool that may complement current clinical assays in early diagnosis and in the prognosis of the severity of preeclampsia to ultimately enable comprehensive prenatal care for all patients.

The effect of progesterone supplementation in women with threatened miscarriage on fetal fraction in non-invasive prenatal testing: A matched case-control study

AIM

To evaluate the effect of progesterone use on fetal fraction (FF) in non-invasive prenatal testing (NIPT) due to the threat of first trimester miscarriage.

METHODS

This case control study included the pregnant who were referred to our clinic for non-invasive prenatal testing. The patients were categorized into three groups: Pregnant women with vaginal bleeding and using progesterone, pregnant women with vaginal bleeding and not using progesterone, and pregnant women without bleeding. The groups were formed by matching gestational week. Women with multiple pregnancy, BMI (body mass index) ≥25, abnormal fetal karyotype, and chronic disease were excluded from the study. Maternal characteristics, FF of the NIPT were recruited from the computer based medical records.

RESULTS

A total of 10,275 NIPT tests were performed during the study period. 3% of the patients (n = 308) were found at risk of miscarriage. 100 patients with a vaginal bleeding and 50 control patients were matched. The median value of the fetal fraction ratio was found to be 6.55 in pregnant women without vaginal bleeding, 7.05 in pregnant women who had vaginal bleeding and using progesterone, and 7.3 in pregnant women who had vaginal bleeding and did not use progesterone. Although the fetal fraction ratio was found to be higher in pregnant women with vaginal bleeding and lower in progesterone users, this situation could not reach the level of statistical significance (p = 0.351).

CONCLUSIONS

The fetal fraction rate in maternal blood is not affected in pregnant women who use progesterone due to vaginal bleeding in early gestational weeks.

Use of cell-free signals as biomarkers for early and easy prediction of preeclampsia

Introduction

Preeclampsia (PE) is a leading cause of maternal and perinatal morbidity worldwide. However, current methods of screening are complicated and require special skill sets. In this observational study of prospectively collected samples, we wanted to evaluate if cell-free (cf) DNA could be an efficient biomarker for identification of at-risk patients.

Methods

One hundred patients attending a private prenatal clinic in Canada were enrolled in their first trimester of pregnancy and a blood draw was carried out at 11 + 0 to 14 + 2 weeks' (timepoint A) and 17 + 6 to 25 + 5 weeks of gestation (timepoint B). CfDNA signals, namely concentration, fetal fraction, and fragment size distribution, were correlated with clinical outcomes in the test population to develop the logistic regression model.

Results

Twelve patients developed PE-four early-stage and eight late-stage PE. Significant differences were observed between PE patients and control cases for all three cfDNA signals at timepoint A, while both fetal fraction and concentration were significantly different between PE patients and control cases at timepoint B. Overall, the model had a sensitivity of up to 100% and specificity of up to 87.5% at Timepoint A.

Conclusion

This proof-of-principle study showed that use of this logistic regression model could identify patients at risk of preeclampsia in the first trimester of pregnancy.

Missing links in preeclampsia cell model systems of endothelial dysfunction

Preeclampsia, one of the main hypertensive disorders of pregnancy, is associated with circulating factors released by the ischemic placenta accompanied by systemic endothelial dysfunction. The etiology of preeclampsia remains poorly understood although it is associated with high maternal and fetal mortality and increased cardiovascular disease risk. Most cell model systems used for studying endothelial dysfunction have not taken into account hemodynamic physical factors such as shear-stress forces which may prevent extrapolation of cell data to in vivo settings. We overview the role of hemodynamic forces in modulating endothelial cell function and discuss strategies to reproduce this biological characteristic in vitro to improve our understanding of endothelial dysfunction associated with preeclampsia.

Maternal Low Volume Circulation Relates to Normotensive and Preeclamptic Fetal Growth Restriction

This narrative review summarizes current evidence on the association between maternal low volume circulation and poor fetal growth. Though much work has been devoted to the study of cardiac output and peripheral vascular resistance, a low intravascular volume may explain why high vascular resistance causes hypertension in women with preeclampsia (PE) that is associated with fetal growth restriction (FGR) and, at the same time, presents with normotension in FGR itself. Normotensive women with small for gestational age babies show normal gestational blood volume expansion superimposed upon a constitutionally low intravascular volume. Early onset preeclampsia (EPE; occurring before 32 weeks) is commonly associated with FGR, and poor plasma volume expandability may already be present before conception, thus preceding gestational volume expansion. Experimentally induced low plasma volume in rodents predisposes to poor fetal growth and interventions that enhance plasma volume expansion in FGR have shown beneficial effects on intrauterine fetal condition, prolongation of gestation and birth weight. This review makes the case for elevating the maternal intravascular volume with physical exercise with or without Nitric Oxide Donors in FGR and EPE, and evaluating its role as a potential target for prevention and/or management of these conditions.

The Influence of Maternal Obesity on Cell-Free Fetal DNA and Blood Pressure Regulation in Pregnancies with Hypertensive Disorders

Background and Objectives: obesity and blood pressure disorders are one of the main risk factors for antenatal, intra, postpartum, and neonatal complications. In preeclampsia (PE), the placental hypoxia leads to vascular endothelium dysfunction, cell necrosis, and apoptosis. This condition is associated with the release of free fetal DNA (cffDNA) circulating in plasma. The disturbance of the efficiency of vasodilatation and blood pressure regulation in PE can be confirmed by analyzing the apelin, salusin, and prosalusin. This study aimed to assess the influence of obesity on cffDNA, and the effectiveness of maintaining normal blood pressure in patients with preeclampsia and gestational hypertension. Material and Methods: the research material was blood serum and oral mucosa swabs, obtained from 168 patients. Pregnant women were divided into the following: a control group (C)-67 women; a gestational hypertension group (GH)-35 patients; a preeclampsia with obesity group (PE + O) (pre-gravid BMI > 30)-23 patients. The rest were lean preeclamptic women (PE)-66 patients-(pre-gravid BMI < 25 in 43 women). Results: the cffDNA was observed in 1.50% of women in the C group, in 2.45% in the GH group, but in 18.18% of lean patients with preeclampsia. The cffDNA was detected in 58% of obese pregnant women with PE. The greater the placental hypoxia was in preeclampsia, the less efficient the hypotensive mechanisms, according to an analysis of the studied adipokines. The prosalusin concentration was significantly lower in the PE group with cffDNA than in the PE group without it (p = 0.008). Apelin was higher in the PE group with cffDNA (p = 0.006) compared to other groups. The same results were also observed in the subgroup with obesity. Conclusion: in preeclamptic women, obesity seems to act as an additive factor of placental damage by means of the dysregulation of hypotensive mechanisms.

Can the Cell-free DNA Test Predict Placenta Accreta Spectrum or Placenta Previa Totalis?

BACKGROUND

Following the discovery that fetal DNA originates from the trophoblastic cells of the placenta, the contribution of the cell-free DNA test in placenta-related obstetric complications has begun to be investigated. Compared to uncomplicated pregnancies, higher fetal fractions were detected in placenta accreta spectrum and placenta previa, which are among placenta-related obstetric complications. However, this data applies only to advanced gestational weeks.

AIM

To investigate the possible predictive value of fetal fraction in cell-free DNA tests in pregnancies with placenta previa and placenta accreta spectrum in early gestational ages.

MATERIALS AND METHODS

This study was conducted in women who were screened via cell-free DNA tests for common aneuploidies in the first and second trimester and subsequently diagnosed with placenta previa or placenta accreta spectrum. After the diagnosis was confirmed with a C-section, fetal fractions were retrospectively compared to a control group with a history of an uncomplicated C-section who were also previously screened by cell-free DNA test.

RESULTS

The median and interquartile range (IQR) of fetal fractions for placenta previa (n=19), placenta accreta spectrum (n=7), and control groups (n=85) were 8.1 (6-10), 6.8 (6.7-10.7), and 7.1 (4.7-9.65), respectively. No statistically significant difference was observed among the three groups in terms of fetal fractions (p=0.587).

CONCLUSIONS

According to our data, we did not observe any relationship between placental invasion abnormalities vs. control group or placenta previa vs. control group using the fetal fractions of the cell-free DNA test. Furthermore, we could not confirm a predictive role and/or any additional clinical contribution. We believe that future studies focusing on placental mRNA might be more helpful than cell-free fetal DNA testing.

Deoxyribonuclease activity negative correlates with extracellular DNA in uncomplicated singleton pregnancies in the third trimester

OBJECTIVES

It is not clear, which factors affect extracellular DNA (ecDNA) concentrations in healthy women with singleton uncomplicated pregnancies, although deoxyribonucleases (DNases) are hypothesized to be responsible for the cleavage of plasma ecDNA. The aim of this study was to analyze potential determinants of total ecDNA including plasma DNase activity.

METHODS

Plasma samples were collected from 48 healthy women with singleton uncomplicated pregnancies in the third trimester (gestation week 37). DNA was isolated and quantified using fluorometry and real time PCR. DNase activity was assessed using the single radial enzyme-diffusion method.

RESULTS

Neither ecDNA, nor DNase activity were affected by maternal age or BMI. DNase activity negatively correlated with total plasma ecDNA (r=-0.40, p=0.007). Similar associations were found for ecDNA of nuclear and mitochondrial origin, but not with fetal DNA quantified using Y-targeted PCR in male fetus-bearing pregnancies.

CONCLUSIONS

The role of plasma ecDNA of fetal and maternal origin is studied in the pathogenesis of pregnancy-complications. The results indicate that plasma DNase activity could negatively regulate ecDNA concentrations and should, thus, be analyzed in preeclampsia, preterm birth and other ecDNA-related pregnancy complications.

At Preeclampsia Diagnosis, Total Cell-Free DNA Concentration is Elevated and Correlates With Disease Severity

Background

Placental derived cell‐free DNA (cfDNA), widely utilized for prenatal screening, may serve as a biomarker for preeclampsia. To determine whether cfDNA parameters are altered in preeclampsia, we conducted a case‐control study using prospectively collected maternal plasma (n=20 preeclampsia, n=22 normal) using our in‐house validated prenatal screening assay.

Methods and Results

Isolated cfDNA was quantified, sequenced using Illumina NextSeq 500, and the placental‐derived fraction was determined. Clinical and test characteristics were compared between preeclampsia and controls, followed by comparisons within the preeclampsia cohort dichotomized by cfDNA concentration. Lastly, cfDNA parameters in preeclampsia were correlated with markers of disease severity. Maternal age, body mass index, gestational age at delivery, cesarean rate, and neonatal birthweight were expectedly different between groups (P≤0.05). The placental‐derived cfDNA fraction did not differ between groups (21.4% versus 16.9%, P=0.06); however, total cfDNA was more than 10 times higher in preeclampsia (1235 versus 106.5 pg/µL, P<0.001). This relationship persisted when controlling for important confounders (OR 1.22, 95% CI 1.04–1.43, P=0.01). The dichotomized preeclampsia group with the highest cfDNA concentration delivered earlier (33.2 versus 36.6 weeks, P=0.02) and had lower placental‐derived fractions (9.1% versus 21.4%, P=0.04). Among preeclampsia cases, higher total cfDNA correlated with earlier gestational age at delivery (P=0.01) and higher maximum systolic blood pressure (P=0.04).

Conclusions

At diagnosis, total cfDNA is notably higher in preeclampsia, whereas the placental derived fraction remains similar to healthy pregnancies. In preeclampsia, higher total cfDNA correlates with earlier gestational age at delivery and higher systolic blood pressure. These findings may indicate increased release of cfDNA from maternal tissue injury.

Nitric oxide-related gene and microRNA expression in peripheral blood in pregnancy vary by self-reported race

Adverse pregnancy outcomes disproportionately affect non-Hispanic (NH) Black patients in the United States. Structural racism has been associated with increased psychosocial distress and inflammation and may trigger oxidative stress. Thus, the nitric oxide (NO) pathway (involved in the regulation of inflammation and oxidative stress) may partly explain the underlying disparities in obstetric outcomes.Cohort study of 154 pregnant patients with high-risk obstetric histories; n = 212 mRNAs and n = 108 microRNAs (miRNAs) in the NO pathway were evaluated in circulating white blood cells. NO pathway mRNA and miRNA transcript counts were compared by self-reported race; NH Black patients were compared with women of other races/ethnicities. Finally, miRNA-mRNA expression levels were correlated.Twenty-two genes (q < 0.10) were differentially expressed in self-identified NH Black individuals. Superoxide dismutase 1 (SOD1), interleukin-8 (IL-8), dynein light chain LC8-type 1 (DYNLL1), glutathione peroxidase 4 (GPX4), and glutathione peroxidase 1 (GPX1) were the five most differentially expressed genes among NH Black patients compared to other patients. There were 63 significantly correlated miRNA-mRNA pairs (q < 0.10) demonstrating potential miRNA regulation of associated target mRNA expression. Ten miRNAs that were identified as members of significant miRNA-mRNA pairs were also differentially expressed among NH Black patients (q < 0.10).These findings support an association between NO pathway and inflammation and infection-related mRNA and miRNA expression in blood drawn during pregnancy and patient race/ethnicity. These findings may reflect key differences in the biology of inflammatory gene dysregulation that occurs in response to the stress of systemic racism and that underlies disparities in pregnancy outcomes.

Circulating Nucleic Acids in Maternal Plasma and Serum in Pregnancy Complications: Are They Really Useful in Clinical Practice? A Systematic Review

OBJECTIVE

A systematic review was carried out to summarize the available evidence to assess whether circulating nucleic acids in maternal plasma and serum (CNAPS) have the potential to serve as extra and independent markers for the prediction and/or progression monitoring of the most common and severe complications of pregnancy, including preeclampsia, intrauterine growth restriction, preterm delivery, morbidly adherent placenta, gestational diabetes, antiphospholipid syndrome, threatened abortion, intrahepatic cholestasis of pregnancy, and hyperemesis gravidarum.

METHOD

A comprehensive literature search of the MEDLINE (PubMed), EMBASE, and ISI Web of Knowledge databases was conducted to identify relevant studies that included amounts of CNAPS in the abovementioned pregnancy complications.

RESULTS

Eighty-three studies met the eligibility criteria. The vast majority of studies were conducted on the quantity of total circulating cell free DNA (cfDNA) and cell free fetal DNA (cffDNA), and some were conducted on messenger RNA (mRNA) species. A few studies have instead evaluated the cell free DNA fetal fraction (cfDNAff), but only in a limited number of pregnancy complications. Despite the growing interest and the abundance of the papers available, little information is available for other new CNAPS, including microRNA (miRNA), long noncoding RNA (lncRNA), mitochondrial DNA (mtDNA), and circular RNA.

CONCLUSION

Due to the heterogeneity of the populations enrolled, the scarcity of the studies that adjusted the CNAPS values for possible confounding factors, and the difficulty in interpreting the published data, no conclusion regarding the statistical robustness and clinical relevance of the data can be made at present. If assayed at the third trimester, the CNAPS have, however, shown better performance, and could be used in populations already at risk of developing complications as suggested by the presence of other clinical features. Other CNAPS, including miRNA, are under investigation, especially for the screening of gestational diabetes mellitus, but no data about their clinical utility are available. Circulating DNA (cfDNA, cffDNA, and cfDNAff) and mRNA have not been properly evaluated yet, especially in patients asymptomatic early in pregnancy but who developed complications later, perhaps because of the high cost of these techniques and the availability of other predictors of pregnancy complications (biochemical, biophysical, and ultrasound markers). Therefore, from the analysis of the data, the positive predictive value is not available. As regards the new CNAPS, including miRNA, there are still no sufficient data to understand if they can be promising markers for pregnancy complications monitoring and screening, since CNAPS are statistically weak and expensive. It is reasonable to currently conclude that the use of the CNAPS in clinical practice is not recommended.

Omics Approaches to Study Formation and Function of Human Placental Syncytiotrophoblast

Proper development of the placenta is vital for pregnancy success. The placenta regulates exchange of nutrients and gases between maternal and fetal blood and produces hormones essential to maintain pregnancy. The placental cell lineage primarily responsible for performing these functions is a multinucleated entity called syncytiotrophoblast. Syncytiotrophoblast is continuously replenished throughout pregnancy by fusion of underlying progenitor cells called cytotrophoblasts. Dysregulated syncytiotrophoblast formation disrupts the integrity of the placental exchange surface, which can be detrimental to maternal and fetal health. Moreover, various factors produced by syncytiotrophoblast enter into maternal circulation, where they profoundly impact maternal physiology and are promising diagnostic indicators of pregnancy health. Despite the multifunctional importance of syncytiotrophoblast for pregnancy success, there is still much to learn about how its formation is regulated in normal and diseased states. ‘Omics’ approaches are gaining traction in many fields to provide a more holistic perspective of cell, tissue, and organ function. Herein, we review human syncytiotrophoblast development and current model systems used for its study, discuss how ‘omics’ strategies have been used to provide multidimensional insights into its formation and function, and highlight limitations of current platforms as well as consider future avenues for exploration.

Mid-pregnancy maternal blood nitric oxide-related gene and miRNA expression are associated with preterm birth

Aim: The nitric oxide (NO) pathway modulates inflammation and may influence birth timing. Patients & methods: Case-control analysis of 136 pregnant women with RNA obtained <28 weeks; n = 212 mRNAs and n = 108 miRNAs in the NO pathway were evaluated. NO-pathway mRNA and miRNA transcript counts in women delivering preterm versus at term were compared, miRNA-mRNA expression levels correlated and prediction models generated. Results: Fourteen genes were differentially expressed in women delivering <37 weeks; 13/14 were also differentially expressed in those delivering <34 weeks (q <0.10) versus term births. Multiple miRNA-mRNA pairs were correlated. Models with gene expression better predicted prematurity than models with only clinical or nongenomic predictors. Conclusion: Maternal blood NO pathway-related mRNA and miRNA expression is associated with prematurity.

The Amniotic Fluid Cell-Free Transcriptome Provides Novel Information about Fetal Development and Placental Cellular Dynamics

The amniotic fluid (AF) is a complex biofluid that reflects fetal well-being during development. AF con be divided into two fractions, the supernatant and amniocytes. The supernatant contains cell-free components, including placenta-derived microparticles, protein, cell-free fetal DNA, and cell-free fetal RNA from the fetus. Cell-free mRNA (cfRNA) analysis holds a special position among high-throughput analyses, such as transcriptomics, proteomics, and metabolomics, owing to its ease of profiling. The AF cell-free transcriptome differs from the amniocyte transcriptome and alters with the progression of pregnancy and is often associated with the development of various organ systems including the fetal lung, skin, brain, pancreas, adrenal gland, gastrointestinal system, etc. The AF cell-free transcriptome is affected not only by normal physiologies, such as fetal sex, gestational age, and fetal maturity, but also by pathologic mechanisms such as maternal obesity, and genetic syndromes (Down, Edward, Turner, etc.), as well as pregnancy complications (preeclampsia, intrauterine growth restriction, preterm birth, etc.). cfRNA in the amniotic fluid originates from the placenta and fetal organs directly contacting the amniotic fluid as well as from the fetal plasma across the placenta. The AF transcriptome may reflect the fetal and placental development and therefore aid in the monitoring of normal and abnormal development.

Circulating Total Cell-Free DNA Levels Are Increased in Hypertensive Disorders of Pregnancy and Associated with Prohypertensive Factors and Adverse Clinical Outcomes

Previous studies have described increased circulating cell-free DNA (cfDNA) in hypertensive disorders of pregnancy (HDP). Here, we aimed first to confirm this information using a simple, but sensible fluorescent assay, and second to investigate whether total cfDNA is associated with circulating factors known to be linked to the pathophysiology of HDP as well as with poor maternal-fetal outcomes. We studied 98 women with healthy pregnancies (HP), 88 with gestational hypertension (GH), and 91 with preeclampsia (PE). Total DNA was extracted from plasma using the QIAamp DNA blood mini kit and quantified using Quant-iT™ PicoGreen® dsDNA fluorescent detection kit. We found higher total cfDNA levels in GH and PE (197.0 and 174.2 ng/mL, respectively) than in HP (140.5 ng/mL; both p < 0.0001). Interestingly, total cfDNA levels were elevated in both male and female-bearing pregnancies diagnosed with either HDP, and in more severe versus less severe HDP cases, as classified according to responsiveness to antihypertensive therapy. In addition, total cfDNA was independently associated with HDP, and a cutoff concentration of 160 ng/mL provided appropriate sensitivity and specificity values for diagnosing GH and PE compared to HP (70-85%, both p < 0.0001). Moreover, high total cfDNA was associated with adverse clinical outcomes (high blood pressure, low platelet count, preterm delivery, fetal growth restriction) and high prohypertensive factors (sFLT-1, sEndoglin, MMP-2). These findings represent a step towards to the establishment of cfDNA as a diagnostic tool and the need to understand its role in HDP.

Implications of non-invasive prenatal testing for identifying and managing high-risk pregnancies

Non-invasive prenatal testing is regularly used to screen for aneuploidies and Rhesus status of a fetus. Since 1997 when free fetal DNA (ffDNA) in the maternal circulation was first identified, it has been hypothesized that it may be possible to use non-invasive prenatal testing (NIPT) to identify high-risk pregnancies including pre-eclampsia, growth restriction and preterm birth. Since then there has been much interest in this area as a way to identify and understand disease processes. This review presents the current evidence for this approach. For pre-eclampsia the hypothesis is that ffDNA would increase but the evidence for this is heterogenous across studies and trimesters. There is however increasing agreement between studies that by the third trimester ffDNA is more likely to be raised in pre-eclamptic patients than controls. For preterm birth, again, the main hypothesis is that ffDNA should increase. The results are also heterogenous, with some studies finding increased ffDNA prior to preterm birth, and others finding no change. For fetal growth restriction, there are competing theories for reduced and increased ffDNA and some studies suggest that levels are raised and some reduced. There are complexities in interpreting all of this evidence as the studies' designs, patient populations, and especially in the context of growth restriction, the definitions are not clear. Furthermore, authors use different biochemical tests and different units to describe their results, making meta-analysis difficult. All of these issues and conflicting findings lead us to the conclusion that currently there is yet no definitive place in clinical practice for NIPT to support the diagnosis and management of high-risk pregnancies. However, it is vital that this research continues as it could open the door to better understanding of the disease process and novel approaches to management.

Maternal total cell-free DNA in preeclampsia with and without intrauterine growth restriction

Elevation of total cell-free DNA (cfDNA) in patients with preeclampsia is well-known; however, whether this change precedes the onset of symptoms remains inconclusive. Here, we conducted a nested case-control study to determine the elevation of cfDNA levels in women who subsequently developed preeclampsia. Methylated HYP2 (m-HYP2) levels were determined in 68 blood samples collected from women with hypertensive disorders of pregnancy, along with 136 control samples, using real-time quantitative PCR. The measured m-HYP2 levels were converted to multiples of the median (MoM) values for correction of maternal characteristics. The m-HYP2 levels and MoM values in patients with preeclampsia were significantly higher than in controls during the third trimester (P < 0.001, both), whereas those for women who subsequently developed preeclampsia did not differ during the second trimester. However, when patients with preeclampsia were divided based on the onset-time of preeclampsia or 10th percentile birth weight, both values were significantly higher in women who subsequently developed early-onset preeclampsia (P < 0.05, both) and preeclampsia with small-for-gestational-age (SGA) neonate (P < 0.01, both) than controls. These results suggested that total cfDNA levels could be used to predict early-onset preeclampsia or preeclampsia with SGA neonate.

Preeclampsia Is a Syndrome with a Cascade of Pathophysiologic Events

This review integrates the currently available information on the molecular, cellular, and systemic mechanisms involved in the pathophysiology of preeclampsia. It highlights that the growth, protection, and promotion of the conceptus requires the modulation of an intact maternal immune system, communication between the mother and fetus, and adaptation of the maternal organic functions. A malfunction in any of these factors, on either side, will result in a failure of the cascade of events required for the normal course of pregnancy. Maladaptive processes, initially aiming to protect the conceptus, fail to anticipate the gradually increasing cardiovascular volume load during the course of pregnancy. As a result, multiple organ dysfunctions install progressively and eventually reach a state where mother and/or fetus are at risk of severe morbidity or even mortality, and where the termination of pregnancy becomes the least harmful solution. The helicopter view on pathophysiologic processes associated with preeclampsia, as presented in this paper, illustrates that the etiology of preeclampsia cannot be reduced to one single mechanism, but is to be considered a cascade of consecutive events, fundamentally not unique to pregnancy.

Transfection of maternal cells with placental extracellular vesicles in preeclampsia

The role of extracellular vesicles is widely studied. As well as other organs, placenta produces extracellular vesicles during both, normal and pathological pregnancies. During pregnancy, placental/fetal free DNA circulates in maternal blood. Concentrations of free placental DNA are much higher when pregnancy complications of various etiologies occur. Such a complication could be preeclampsia. In our previous animal model, administration of pure DNA isolated from fetus did not induce any prenatal complications. Here we hypothesize that in real life during preeclampsia or other pregnancy complications, placental DNA might be transported by extracellular vesicles to maternal cells. Also, our preliminary data prove that placental DNA is present in circulating exosomes in maternal blood. Therefore, a lipid bilayer of extracellular vesicles could protect DNA from degradation by enzymes. Extracellular vesicles tend to merge with other cells, therefore, following expression of fetal genes from placental extracellular vesicles in maternal cells could lead to an immune response already observed in pregnancy complications. Future studies should be mainly focused on verification of our hypothesis and evaluate the potential of placental/fetal extracellular vesicles and their gene transfer in preeclampsia or other pregnancy complications.

Can fetal fractions in the cell-free DNA test predict the onset of fetal growth restriction?

Objective To investigate the possible predictive value of fetal fraction in the cell-free DNA (cfDNA) test in pregnancies with early- and late-onset fetal growth restriction (FGR). Methods This retrospective study comprised 247 women who were screened using the cfDNA test for aneuploidies during the first or second trimester and had deliveries at our institution from January 2016 to December 2019. The fetal fractions of women with early- (n = 14) and late-onset (n = 83) FGR and those with uncomplicated pregnancies (n = 150) were compared. Results The median fetal fractions for the early-onset FGR, late-onset FGR, and control groups were 5.7 [interquartile range (IQR) 2.65], 7 (IQR 5), and 7.35 (IQR 3.65), respectively. The fetal fractions were significantly lower in the early-onset FGR group than in the late-onset FGR and control groups (P = 0.047 and P = 0.037, respectively). There was no difference in fetal fractions between the late-onset FGR and control groups (P = 1.00). Conclusion As a placenta-related disease, early-onset FGR had lower fetal fractions in the cfDNA test than uncomplicated pregnancies. For clinical use, lower fetal fractions can contribute as a biomarker for screening asymptomatic women for possible placenta-related diseases, such as early-onset FGR. However, more studies are needed to define the "lower" limit.

Whole-Genome Promoter Profiling of Plasma DNA Exhibits Diagnostic Value for Placenta-Origin Pregnancy Complications

Placenta-origin pregnancy complications, including preeclampsia (PE), gestational diabetes mellitus (GDM), fetal growth restriction (FGR), and macrosomia (MA) are common occurrences in pregnancy, resulting in significant morbidity and mortality for both mother and fetus. However, despite their frequency, there are no reliable methods for the early diagnosis of these complications. Since cfDNA is mainly derived from placental trophoblasts and maternal hematopoietic cells, it might have information for gene expression which can be used for disease prediction. Here, low coverage whole-genome sequencing on plasma DNA from 2,199 pregnancies is performed based on retrospective cohorts of 3,200 pregnant women. Read depth in the promoter regions is examined to define read-depth distribution patterns of promoters for pregnancy complications and controls. Using machine learning methods, classifiers for predicting pregnancy complications are developed. Using these classifiers, complications are successfully predicted with an accuracy of 80.3%, 78.9%, 72.1%, and 83.0% for MA, FGR, GDM, and PE, respectively. The findings suggest that promoter profiling of cfDNA may be used as a biological biomarker for predicting pregnancy complications at early gestational age.

Atypical hemolytic uremic syndrome and complement blockade: established and emerging uses of complement inhibition

PURPOSE OF REVIEW

Atypical hemolytic uremic syndrome (aHUS) is a diagnosis that has captured the interest of specialists across multiple fields. The hallmark features of aHUS are microangiopathic hemolysis and thrombocytopenia, which creates a diagnostic dilemma because of the occurrence of these findings in a wide variety of clinical disorders.

RECENT FINDINGS

In most of the instances, aHUS is a diagnosis of exclusion after ruling out causes such as Shigella toxin, acquired or genetic a disintegrin and metalloproteinase thrombospondin motif 13 deficiency (thrombotic thrombocytopenic purpura), and vitamin B12 deficiency. In the purest sense, aHUS is a genetic condition that is activated (or unmasked) by an environmental exposure. However, it is now evident that complement activation is a feature of many diseases. Variants in complement regulatory genes predispose to microangiopathic hemolysis in many rheumatologic, oncologic, and drug-induced vascular, obstetric, peritransplant, and infectious syndromes.

SUMMARY

Many 'hemolysis syndromes' overlap clinically with aHUS, and we review the literature on the treatment of these conditions with complement inhibition. New reports on the treatment of C3 glomerulopathy, Shiga toxin-related classic hemolytic uremic syndrome, and medication-related thrombotic microangiopathy will be reviewed as well.

Cell-Free Fetal DNA Increases Prior to Labor at Term and in a Subset of Preterm Births

Cell-free fetal DNA in the maternal circulation has been associated with the onset of labor at term. Moreover, clinical studies have suggested that cell-free fetal DNA has value to predict pregnancy complications such as spontaneous preterm labor leading to preterm birth. However, a mechanistic link between cell-free fetal DNA and preterm labor and birth has not been established. Herein, using an allogeneic mouse model in which a paternal green fluorescent protein (GFP) can be tracked in the fetuses, we established that cell-free fetal DNA (Egfp) concentrations were higher in late gestation compared to mid-pregnancy and were maintained at increased levels during the onset of labor at term, followed by a rapid decrease after birth. A positive correlation between cell-free fetal DNA concentrations and the number of GFP-positive pups was also observed. The increase in cell-free fetal DNA concentrations prior to labor at term was not linked to a surge in any specific cytokine/chemokine; yet, specific chemokines (i.e., CCL2, CCL7, and CXCL2) increased as gestation progressed and maintained elevated levels in the postpartum period. In addition, cell-free fetal DNA concentrations increased prior to systemic inflammation-induced preterm birth, which was associated with a strong cytokine response in the maternal circulation. However, cell-free fetal DNA concentrations were not increased prior to intra-amniotic inflammation-induced preterm birth, but in this model, a mild inflammatory response was observed in the maternal circulation. Collectively, these findings suggest that an elevation in cell-free fetal DNA concentrations in the maternal circulation precedes the physiological process of labor at term and the pathological process of preterm labor linked with systemic inflammation, but not that associated with intra-amniotic inflammation.

The Cellular Transcriptome in the Maternal Circulation During Normal Pregnancy: A Longitudinal Study

Pregnancy represents a unique immunological state in which the mother adapts to tolerate the semi-allogenic conceptus; yet, the cellular dynamics in the maternal circulation are poorly understood. Using exon-level expression profiling of up to six longitudinal whole blood samples from 49 pregnant women, we undertook a systems biology analysis of the cellular transcriptome dynamics and its correlation with the plasma proteome. We found that: (1) chromosome 14 was the most enriched in transcripts differentially expressed throughout normal pregnancy; (2) the strongest expression changes followed three distinct longitudinal patterns, with genes related to host immune response (e.g., MMP8, DEFA1B, DEFA4, and LTF) showing a steady increase in expression from 10 to 40 weeks of gestation; (3) multiple biological processes and pathways related to immunity and inflammation were modulated during gestation; (4) genes changing with gestation were among those specific to T cells, B cells, CD71+ erythroid cells, natural killer cells, and endothelial cells, as defined based on the GNF Gene Expression Atlas; (5) the average expression of mRNA signatures of T cells, B cells, and erythroid cells followed unique patterns during gestation; (6) the correlation between mRNA and protein abundance was higher for mRNAs that were differentially expressed throughout gestation than for those that were not, and significant mRNA-protein correlations were observed for genes part of the T-cell signature. In summary, unique changes in immune-related genes were discovered by longitudinally assessing the cellular transcriptome in the maternal circulation throughout normal pregnancy, and positive correlations were noted between the cellular transcriptome and plasma proteome for specific genes/proteins. These findings provide insights into the immunobiology of normal pregnancy.

Fetal fraction and noninvasive prenatal testing: What clinicians need to know

The fetal fraction (FF) is a function of both biological factors and bioinformatics algorithms used to interpret DNA sequencing results. It is an essential quality control component of noninvasive prenatal testing (NIPT) results. Clinicians need to understand the biological influences on FF to be able to provide optimal post-test counseling and clinical management. There are many different technologies available for the measurement of FF. Clinicians do not need to know the details behind the bioinformatics algorithms of FF measurements, but they do need to appreciate the significant variations between the different sequencing technologies used by different laboratories. There is no universal FF threshold that is applicable across all platforms and there have not been any differences demonstrated in NIPT performance by sequencing platform or method of FF calculation. Importantly, while FF should be routinely measured, there is not yet a consensus as to whether it should be routinely reported to the clinician. The clinician should know what to expect from a standard test report and whether reasons for failed NIPT results are revealed. Emerging solutions to the challenges of samples with low FF should reduce rates of failed NIPT in the future. In the meantime, having a "plan B" prepared for those patients for whom NIPT is unsuccessful is essential in today's clinical practice.

Screening for preeclampsia in the first trimester of pregnancy in routine clinical practice in Hungary

We aimed to evaluate the contribution of different factors in the Fetal Medicine Foundation algorithms for preeclampsia (PE) risk calculation during first-trimester screening in Hungary. We selected subjects for the nested case-control study from a prospective cohort of 2545 low-risk pregnancies. Eighty-two patients with PE and 82 gestational age-matched controls were included. Individual PE risk was calculated using two risk-assessing softwares. Using Astraia 2.3.1, considering maternal characteristics and biophysical parameters only, detection rates (DR) were 63.6% for early-PE and 67.6% for late-PE. When we added placenta associated plasma protein A (PAPP-A) to the risk calculation, DRs decreased to 54.5% and 64.8% respectively. Using Astraia 2.8.2 with maternal characteristics and biophysical parameters resulted in the DRs of 63.6% (early-PE) and 56.3% (late-PE). If we added PAPP-A to the risk calculation, DRs improved to 72.7% and 54.9%. The addition of placental growth factor (PlGF) did not increase detection rates in either calculation. In conclusion, using maternal characteristics, biophysical parameters, and PAPP-A, an acceptable screening efficacy could be achieved for early-PE during first-trimester screening. Since PlGF did not improve efficacy in our study, we suggest setting new standard curves for PlGF in Eastern European pregnant women, and the evaluation of novel biochemical markers.