Free fetal DNA is not increased before 20 weeks in intrauterine growth restriction or pre-eclampsia

Association between fetal fraction of cell-free DNA and adverse pregnancy outcomes

PURPOSE

To determine the association between fetal fraction (FF) levels in cell-free fetal DNA (cffDNA) testing and adverse pregnancy outcomes.

METHODS

This retrospective cohort study, conducted at a single center, involved 2063 pregnant women with normal 1st and 2nd trimester non-invasive prenatal test (NIPT) results between 2016 and 2021. Pregnancy outcomes were examined by determining the  < 4% and  < 5th percentile (3.6%) cut-off values for low fetal fraction (LFF). Pregnancy outcomes were also examined by dividing the FF into population-based quartiles. Adverse pregnancy outcomes were pregnancy-induced hypertensive diseases (PIHD), gestational diabetes mellitus (GDM), spontaneous preterm birth (PTB), intrahepatic cholestasis of pregnancy (ICP), small for gestational age (SGA), large for gestational age (LGA), low birth weight (LBW), macrosomia, and 1st and 5th minutes low APGAR scores (< 7).

RESULTS

PIHD was significantly higher in LFF (< 4% and  < 5th percentile) cases (p = 0.015 and p < 0.001, respectively). However, in population-based quartiles of FF, PIHD did not differ significantly between groups. Composite adverse maternal outcomes were significantly higher in the FF < 4% group (p = 0.042). When analyzes were adjusted for maternal age, BMI, and gestational age at NIPT, significance was maintained at  < 4%,  < 5th percentile LFF for PIHD, and  < 4% LFF for composite adverse maternal outcomes. However, there was no significant relationship between LFF with GDM, ICP and PTB. Additionally, there was no significant association between low APGAR scores, SGA, LGA, LBW, macrosomia, and LFF concerning neonatal outcomes.

CONCLUSION

Our study showed that LFF in pregnant women with normal NIPT results may be a predictor of subsequent PIHD.

Obstetrical, perinatal, and genetic outcomes associated with nonreportable prenatal cell-free DNA screening results

BACKGROUND

The clinical implications of nonreportable cell-free DNA screening results are uncertain, but such results may indicate poor placental implantation in some cases and be associated with adverse obstetrical and perinatal outcomes.

OBJECTIVE

This study aimed to assess the outcomes of pregnancies with nonreportable cell-free DNA screening in a cohort of patients with complete genetic and obstetrical outcomes.

STUDY DESIGN

This was a prespecified secondary analysis of a multicenter prospective observational study of prenatal cell-free DNA screening for fetal aneuploidy and 22q11.2 deletion syndrome. Participants who underwent cell-free DNA screening from April 2015 through January 2019 were offered participation. Obstetrical outcomes and neonatal genetic testing results were collected from 21 primary-care and referral centers in the United States, Europe, and Australia. The primary outcome was risk for adverse obstetrical and perinatal outcomes (aneuploidy, preterm birth at <28, <34, and <37 weeks' gestation, preeclampsia, small for gestational age or birthweight <10th percentile for gestational week, and a composite outcome that included preterm birth at <37 weeks, preeclampsia, small for gestational age, and stillbirth at >20 weeks) after nonreportable cell-free DNA screening because of low fetal fraction or other causes. Multivariable analyses were performed, adjusting for variables known to be associated with obstetrical and perinatal outcomes, nonreportable results, or fetal fraction.

RESULTS

In total, 25,199 pregnant individuals were screened, and 20,194 were enrolled. Genetic confirmation was missing in 1165 (5.8%), 1085 (5.4%) were lost to follow-up, and 93 (0.5%) withdrew; the final study cohort included 17,851 (88.4%) participants who had cell-free DNA, fetal or newborn genetic confirmatory testing, and obstetrical and perinatal outcomes collected. Results were nonreportable in 602 (3.4%) participants. A sample was redrawn and testing attempted again in 427; in 112 (26.2%) participants, results were again nonreportable. Nonreportable results were associated with higher body mass index, chronic hypertension, later gestational age, lower fetal fraction, and Black race. Trisomy 13, 18, or 21 was confirmed in 1.6% with nonreportable tests vs 0.7% with reported results (P=.013). Rates of preterm birth at <28, 34, and 37 weeks, preeclampsia, and the composite outcome were higher among participants with nonreportable results, and further increased among those with a second nonreportable test, whereas the rate of small for gestational age infants was not increased. After adjustment for confounders, the adjusted odds ratios were 2.2 (95% confidence interval, 1.1-4.4) and 2.6 (95% confidence interval, 0.6-10.8) for aneuploidy, and 1.5 (95% confidence interval, 1.2-1.8) and 2.1 (95% confidence interval, 1.4-3.2) for the composite outcome after a first and second nonreportable test, respectively. Of the patients with nonreportable tests, 94.9% had a live birth, as opposed to 98.8% of those with reported test results (adjusted odds ratio for livebirth, 0.20 [95% confidence interval, 0.13-0.30]).

CONCLUSION

Patients with nonreportable cell-free DNA results are at increased risk for a number of adverse outcomes, including aneuploidy, preeclampsia, and preterm birth. They should be offered diagnostic genetic testing, and clinicians should be aware of the increased risk of pregnancy complications.

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.

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.

[Cell-free DNA fraction: Can it be used to evaluate the risk of obstetrical issues?]

OBJECTIVE

The aim of the study was to evaluate if fetal cell-free DNA (cfDNA) fraction circulating in maternal blood at the beginning of the second trimester is associated with obstetrical complications.

METHODS

This is a retrospective unicentric study conducted at the hospital of Poissy Saint Germain between the 1^st January 2015, and the 31^st. December 2016, Each woman who had a genetic counseling in order to realize a non-invasive prenatal test (NIPT) was included. Only singleton pregnancies with a documented-issue were analysed. The primary criteria was a composite criteria, defined as the occurrence of preeclampsia, in utero fetal growth, or a spontaneous preterm delivery. A descriptive analyse was first conducted, secondly completed by a sub-group one: "high fetal fraction" (>90^th percentile) group, "low fetal-fraction" group (<10^th percentile) and "medium fetal-fraction" (control group) group.

RESULTS

A total of 417 women had a cfDNA test, which was performed at a mean gestational age of 17.1 weeks of gestation. A total of 17% of pregnancies met the primary criteria. Among them, there were 8 (1.9%) pre-eclampsia, 49 (11.8%) intra-uterine growth restriction and 14 (3.4%) preterm births. There was no significant difference for the occurrence of the primary criteria (P>0.99) and of each obstetrical complication between each group.

CONCLUSION

Fetal cf-DNA fraction measured at the beginning of the second trimester is not associated with common obstetrical complications.

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

Objectives

Preeclampsia and fetal growth restriction are obstetrical syndromes associated with abnormal placental implantation and changes in the activation status of maternal leukocytes. This study is aimed to determine by a simple, rapid fluorescent assay the changes in maternal serum total cell-free DNA (t-cfDNA) concentrations in women with preeclampsia and those with fetal growth restriction (FGR).

Study design

A cross-sectional study was conducted measuring maternal serum t-cfDNA concentrations. Women were classified into the following groups: 1) patients with preeclampsia (n = 21); 2) FGR-estimated fetal weight below the 10^thpercentile (n = 28); and 3) normal pregnancy (n = 39). Serum samples were directly assayed for t-cfDNA using a rapid fluorescent SYBR Gold assay. Elevated maternal serum t-cfDNA concentrations were defined as a cutoff>850ng/ml. Nonparametric statistics were used for analysis.

Results

Women with preeclampsia had a higher median maternal serum concentration (802 ng/ml, 400–2272 ng/ml) than women with a normal pregnancy (499 ng/ml, 0–1892 ng/ml, p = 0.004) and those with FGR (484 ng/ml, 72–2187 ng/ml, p = 0.012). Moreover, even patients with FGR <5^th percentile and abnormal Doppler had a lower median maternal serum t-cfDNA than those with preeclampsia (median 487 ng/ml, 144–1971 ng/ml, p = 0.022). The median concentration of t-cfDNA did not differ between women with a normal pregnancy and those with FGR (p = 0.54), as well as those with fetuses <5th percentile and abnormal Doppler (p = 0.7). Women with preeclampsia had a higher proportion of elevated t-cfDNA than those with a normal pregnancy (p = 0.015) and patients with FGR (p = 0.025).

Conclusions

Preeclampsia is associated with higher maternal serum t-cfDNA concentration than normal pregnancy or FGR. This observation may reflect an increased systemic activation of the maternal inflammation, rather than placental; this assumption is supported by the fact that we did not observe a significant change in the maternal serum t-cfDNA in patients with placental-mediated FGR.

Hypertension in Pregnancy: Defining Blood Pressure Goals and the Value of Biomarkers for Preeclampsia

Hypertensive disorders in pregnancy have been the cause of much clinical dilemma, affecting up to 10 % of all pregnancies. The precise blood pressure to achieve in a pregnant woman is usually a battle between minimizing end organ damage to the mother and providing adequate perfusion to the placenta and the fetus. This predicament is becoming more, not less, frequent as maternal ages increase in high resource nations. Biomarkers to predict preeclampsia, a subcategory of hypertension in pregnancy, have always been elusive. The discovery of angiogenic factors relevant to preeclampsia in the last decade, however, has propelled much needed research, both in the basic science and clinical arenas. In this review, we summarize the latest clinical studies and international guidelines on blood pressure goals in pregnancy, and discuss the most promising of biomarkers to predict or diagnose preeclampsia.

Total and Fetal Circulating Cell-Free DNA, Angiogenic, and Antiangiogenic Factors in Preeclampsia and HELLP Syndrome

BACKGROUND

Preeclampsia (PE) is a hypertensive disorder of pregnancy characterized by hypertension and proteinuria. The HELLP syndrome is the most severe form of PE. The aim of the present study was to determine different potential biomarkers that may help us perform an early diagnosis of the disease, assess on the severity of the disease, and/or predict maternal or fetal adverse outcomes.

METHODS

We measured serum levels of total and fetal circulating cell-free DNA (cfDNA), soluble endoglin, soluble form of vascular endothelial growth factor receptor, and placental growth factor in a healthy control group of pregnant women (n = 26), patients with mild (n = 37) and severe PE (n = 25), and patients with HELLP syndrome (n = 16).

RESULTS

We observed a gradual and strong relationship between all the biomarkers mentioned and the range of severity of PE, with the highest levels in patients with HELLP syndrome. Nevertheless, only the values of total cfDNA were able to significantly differentiate severe PE and HELLP syndrome (20957 ± 2784 vs. 43184 ± 8647 GE/ml, P = 0.01). Receiver operating characteristic (ROC) curves were constructed (i) for the healthy group with respect to the groups with PE and (ii) for patients with PE with respect to the group with HELLP syndrome; sensitivity and specificity values at different cutoff levels were calculated in each case. The maximum ROC area under the curve value for PE and HELLP syndrome (with respect to controls) was 0.91 (P < 0.001).

CONCLUSIONS

The measured biomarkers of cell damage, angiogenesis, and antiangiogenesis may reflect the severity of PE, with higher levels in patients who develop HELLP syndrome. In addition, these biomarkers may also help predict adverse fetal and maternal outcomes.

Cell-Free Total and Fetal DNA in First Trimester Maternal Serum and Subsequent Development of Preeclampsia

Objective The objective of this study was to assess the relationship between first trimester cell-free total and fetal DNA in maternal plasma and the subsequent development of preeclampsia. Study Design Nested case-control study of patients enrolled in the Combined Antioxidant and Preeclampsia Prediction Studies prediction study of 175 women who did and 175 women who did not develop preeclampsia. The predictive values of cell-free total and fetal DNA and the subsequent development of preeclampsia were measured using receiver operating characteristic curves. Results Cell-free total DNA was higher in African American (median; 25-75%; 6.15; 0.14-28.73; p = 0.02) and Hispanic (4.95; 0.20-26.82; p = 0.037) compared with white women (2.33; 0.03-13.10). Levels of cell-free total DNA were also associated with maternal body mass index (BMI) (p = 0.02). Cell-free total DNA levels were similar between women who later developed preeclampsia (3.52; 0.11-25.3) and controls (3.74; 0.12-21.14, p = 0.96). Conclusion There is no significant difference in levels of cell-free total DNA in the first trimester in women who subsequently develop preeclampsia. Levels of cell-free total DNA in the first trimester are increased in African American and Hispanic compared with white women, and levels increase with increasing BMI.

Antenatal Hospitalizations Among Pregnancies Conceived With and Without Assisted Reproductive Technology

OBJECTIVE

To describe the prevalence of antenatal hospitalizations, compare characteristics of women with and without antenatal hospitalizations, and compare timing, length of stay, and reason for hospitalization among pregnancies conceived with and without assisted reproductive technology (ART).

METHODS

We performed a retrospective cohort analysis using linked ART surveillance, vital records, and hospital discharge data from Michigan to calculate the hospitalization ratio as the number of antenatal admissions per 100 live birth deliveries for ART and non-ART deliveries during 2004-2012 and compare trends by ART status. We then restricted analysis to 2008-2012 and used logistic, multinomial, and Poisson regression analysis to model antenatal admissions, trimester of admission, and length of stay, respectively, for ART compared with non-ART deliveries. We examined reason for hospitalization by ART status.

RESULTS

Between 2004 and 2012, the hospitalization ratio for ART deliveries decreased from 14.6 to 12.3 per 100 deliveries (P<.001). Of 557,708 live deliveries during 2008-2012, 22,763 (4.1%) had an antenatal hospitalization. Assisted reproductive technology was a risk factor for having any antenatal admission (singletons adjusted risk ratio [RR] 1.63, 95% confidence interval [CI] 1.43-1.83; multiples adjusted RR 1.24, 95% CI 1.12-1.38) and two or more admissions (singletons adjusted RR 1.86, 95% CI 1.25-2.75; multiples adjusted RR 1.33, 95% CI 1.14-1.54). The percent of time (days) hospitalized during the antenatal period was greater for ART deliveries than non-ART deliveries (singleton adjusted RR 1.28, 95% CI 1.09-1.51; multiples adjusted RR 1.14, 95% CI 1.01-1.29). The most common reason for antenatal admission was preterm labor among all non-ART and multiple gestation deliveries and vaginal bleeding among ART singleton gestations.

CONCLUSION

Deliveries after ART were associated with increased risk of antenatal admissions and longer hospitalizations compared with non-ART deliveries.

Early Prediction of Hypertensive Disorders of Pregnancy Using Cell-Free Fetal DNA, Cell-Free Total DNA, and Biochemical Markers

OBJECTIVE

To evaluate the predictive value of separate and combined tests using cell-free fetal DNA (cffDNA), cell-free total DNA (cfDNA), and biochemical markers for the early detection of pregnancies with hypertensive disorders.

METHODS

A nested case-control study was conducted with 135 singleton pregnancies including 17 gestational hypertension cases, 34 preeclampsia (PE) cases, and 84 controls. We performed real-time quantitative PCR to measure levels of DSCR3 and RASSF1A as cffDNA markers and HYP2 as a cfDNA marker in the first and early second trimesters. Levels of pregnancy-associated plasma protein A (PAPP-A), α-fetoprotein, β-human chorionic gonadotropin, unconjugated estriol, and inhibin A were also determined.

RESULTS

Compared with controls, the median levels and multiples of the median (MoM) values of HYP2 were significantly higher in the PE and hypertensive disorders of pregnancy (HDP) groups at 6-14 and 15-23 weeks. Frist-trimester PAPP-A MoM was significantly lower in PE and HDP than in controls. For PE and HDP, the best model included the first-trimester DSCR3, HYP2, and PAPP-A MoM values achieving detection rates of 67 and 58% at a fixed 10% false-positive rate, respectively [area under the receiver operating characteristic curve 0.832 (95% CI 0.689-0.928) for PE; 0.751 (0.607-0.863) for HDP].

DISCUSSION

The study demonstrates the potential utility of combined first-trimester cffDNA, cfDNA, and PAPP-A for the early prediction of PE.

Quantification and Application of Potential Epigenetic Markers in Maternal Plasma of Pregnancies with Hypertensive Disorders

The aim of this study was to evaluate quantitative aberrations of novel fetal-specific epigenetic markers in maternal plasma of pregnancies with hypertensive disorders. We compared the concentrations of DSCR3, RASSF1A, and SRY as cell-free fetal DNA markers in 188 normal pregnancies, 16 pregnancies with early-onset preeclampsia (EO-PE), 47 pregnancies with late-onset preeclampsia (LO-PE), and 29 pregnancies with gestational hypertension (GH). The concentrations of all markers were significantly correlated with gestational age (p < 0.001 for all). Strong positive correlations were also observed between DSCR3 and SRY (r = 0.471, p < 0.001), as well as between RASSF1A and SRY (r = 0.326, p = 0.015) and between DSCR3 and RASSF1A (r = 0.673, p < 0.001). The concentrations of DSCR3 and RASSF1A in the EO-PE were significantly higher at 24–32 weeks and onwards (p < 0.05 for both). In the LO-PE, DSCR3 and RASSF1A concentrations were significantly higher only at 33–41 weeks compared with the controls. The concentrations of all markers in the GH group were not significantly different from those in the control group. This study is the first demonstration that DSCR3 is a novel epigenetic marker that can be an alternative to the RASSF1A for the prediction of EO-PE.

Noninvasive nucleic acid-based approaches to monitor placental health and predict pregnancy-related complications

During pregnancy, the placenta releases a variety of nucleic acids (including deoxyribonucleic acid, messenger ribonucleic acid, or microribonucleic acids) either as a result of cell turnover or as an active messaging system between the placenta and cells in the maternal body. The profile of released nucleic acids changes with the gestational age and has been associated with maternal and fetal parameters. It also can directly reflect pathological changes in the placenta. Nucleic acids may therefore provide a rich source of novel biomarkers for the prediction of pregnancy complications. However, their utility in the clinical setting depends, first, on overcoming some technical considerations in their quantification, and, second, on developing a better understanding of the factors that influence their function and abundance.

The role of shed placental DNA in the systemic inflammatory syndrome of preeclampsia

Preeclampsia is a syndrome occurring only in pregnancy characterized by systemic maternal inflammation and associated with the presence of the placenta. How these 2 aspects of the disease are linked has been the subject of numerous theories and ideas. Recently, there has been increasing interest in DNA shed from the placenta into the maternal circulation as a potential agent initiating the inflammatory response. This review will discuss the current evidence and future directions for placental DNA as the linking factor in preeclampsia in the context of other hypotheses.

Immune Reactivation by Cell-Free Fetal DNA in Healthy Pregnancies Re-Purposed to Target Tumors: Novel Checkpoint Inhibition in Cancer Therapeutics

The role of the immune system in cancer progression has become increasingly evident over the past decade. Chronic inflammation in the promotion of tumorigenesis is well established, and cancer-associated tolerance/immune evasion has long been appreciated. Recent developments of immunotherapies targeting cancer-associated inflammation and immune tolerance, such as cancer vaccines, cell therapies, neutralizing antibodies, and immune checkpoint inhibitors, have shown promising clinical results. However, despite significant therapeutic advances, most patients diagnosed with metastatic cancer still succumb to their malignancy. Treatments are often toxic, and the financial burden of novel therapies is significant. Thus, new methods for utilizing similar biological systems to compare complex biological processes can give us new hypotheses for combating cancer. One such approach is comparing trophoblastic growth and regulation to tumor invasion and immune escape. Novel concepts regarding immune activation in pregnancy, especially reactivation of the immune system at labor through toll like receptor engagement by fetal derived DNA, may be applicable to cancer immunotherapy. This review summarizes mechanisms of inflammation in cancer, current immunotherapies used in the clinic, and suggestions for looking beyond oncology for novel methods to reverse cancer-associated tolerance and immunologic exhaustion utilizing mechanisms encountered in normal human pregnancy.

Maternal plasma cell-free DNA in the prediction of pre-eclampsia

OBJECTIVES

To examine whether maternal plasma concentrations of total cell-free (cf)DNA and fetal fraction at 11-13 and 20-24 weeks' gestation in pregnancies that subsequently develop pre-eclampsia (PE) are different from those without this complication.

METHODS

Total cfDNA and fetal fraction were measured in 20 cases of early PE requiring delivery at < 34 weeks, in 20 cases of late PE with delivery at ≥ 34 weeks and in 200 normotensive controls, at 11-13 and 20-24 weeks' gestation. Total cfDNA and fetal fraction measured at 11-13 weeks were converted to multiples of the median (MoM), corrected for maternal characteristics and gestational age. The distributions of total cfDNA and fetal fraction at 20-24 weeks were expressed as MoM of values at 11-13 weeks. The Mann-Whitney U-test was used to determine the significance of differences in the median values in each outcome group relative to that in the controls.

RESULTS

In the early-PE group at 11-13 weeks, compared with controls, there was a significant increase in median total cfDNA (2104 genome equivalents (GE)/mL vs 1590 GE/mL) and a decrease in median fetal fraction (6.8% vs 8.7%). In the late-PE group at 20-24 weeks, compared with controls, there was a significant decrease in median fetal fraction (8.2% vs 9.6%). These significant differences between groups were not observed when the values were converted to MoM.

CONCLUSION

Measurements of total cfDNA and fetal fraction in maternal plasma at 11-13 and 20-24 weeks are not predictive of PE.

Cell-free fetal DNA and pregnancy-related complications (review)

Cell-free fetal DNA (cff-DNA) is a novel promising biomarker that has been applied in various aspects of obstetrical research, notably in prenatal diagnosis and complicated pregnancies. It is easily detected by semi-quantitative PCR for the SRY target gene. It is well recognized that the levels of circulating cff-DNA play a role in various complications of pregnancy. In this review, we explore the implications of the detection of cff-DNA in a range of pregnancy-related complications, such as preeclampsia, intrauterine growth restriction (IUGR), preterm labor, placenta previa and hyperemesis gravidarum. cff-DNA is released due to apoptotic mechanisms occurring on trophoblastic cells, although recent in vivo studies support the existence of additional mechanisms. The increase in the levels of cff-DNA can be used to predict pregnancy-related complications and has great value in the field of prenatal diagnosis and in common pregnancy-related complications, as it precedes the clinical symptoms of the disease. Gestational age is a factor that determines the elevation in cff-DNA levels in response to pathological conditions. In conclusion, the detection of cff-DNA levels has a number of valuable applications in prenatal screening; however, the detection of cff-DNA levels has not yet been applied in clinical practice for the diagnosis of pregnancy-related disorders. Thus, studies are focusing on unraveling the etiology of alterations in its levels under pathological conditions during pregnancy, in order to determine the potenial predictive and diagnostic applications of this biomarker.

Pre-eclampsia part 2: prediction, prevention and management

An antiangiogenic state might constitute a terminal pathway for the multiple aetiologies of pre-eclampsia, especially those resulting from placental abnormalities. The levels of angiogenic and antiangiogenic proteins in maternal blood change prior to a diagnosis of pre-eclampsia, correlate with disease severity and have prognostic value in identifying women who will develop maternal and/or perinatal complications. Potential interventions exist to ameliorate the imbalance of angiogenesis and, hence, might provide opportunities to improve maternal and/or perinatal outcomes in pre-eclampsia. Current strategies for managing pre-eclampsia consist of controlling hypertension, preventing seizures and timely delivery of the fetus. Prediction of pre-eclampsia in the first trimester is of great interest, as early administration of aspirin might reduce the risk of pre-eclampsia, albeit modestly. Combinations of biomarkers typically predict pre-eclampsia better than single biomarkers; however, the encouraging initial results of biomarker studies require external validation in other populations before they can be used to facilitate intervention in patients identified as at increased risk. Angiogenic and antiangiogenic factors might also be useful in triage of symptomatic patients with suspected pre-eclampsia, differentiating pre-eclampsia from exacerbations of pre-existing medical conditions and performing risk assessment in asymptomatic women. This Review article discusses the performance of predictive and prognostic biomarkers for pre-eclampsia, current strategies for preventing and managing the condition and its long-term consequences.

Can the quantity of cell-free fetal DNA predict preeclampsia: a systematic review

OBJECTIVE

Previous studies have demonstrated an increase in the quantity of cell-free fetal DNA (cffDNA) before the onset of preeclampsia. It would be beneficial if the quantity of cffDNA predicted preeclampsia in order to implement preventative trials and strategies to decrease maternal and fetal morbidity. Our objective was to review the literature on using cffDNA levels as a predictor of preeclampsia.

METHODS

We performed a systematic review following the Meta-analyses and Systematic Review of Observational Studies guidelines. Included studies evaluated cffDNA levels in pregnant women before the clinical onset of preeclampsia.

RESULTS

Thirteen studies met inclusion criteria. There was considerable heterogeneity between included studies, and all received a quality grade of C on the Grading of Recommendations Assessment, Development, and Evaluation scale. Of the 13 studies, 11 found an increase in cffDNA among pregnant women who subsequently developed preeclampsia. In addition, all four studies analyzing early-onset or severe preeclampsia found significantly elevated cffDNA levels prior to disease onset.

CONCLUSION

Cell-free fetal DNA quantification is a promising marker for preeclampsia prediction, especially for the development of early-onset or severe preeclampsia. However, because of the heterogeneity in published studies, a precise conclusion about the statistical and clinical relevance cannot be made.

Quantification of maternal serum cell-free fetal DNA in early-onset preeclampsia

The aim of this study was to determine whether the increased serum cell-free fetal DNA (cffDNA) level of gravidas developed into early-onset preeclampsia (EOPE) subsequently in the early second trimesters is related to prenatal screening markers. Serum was collected from 1011 gravidas. The level of cffDNA and prenatal screening markers were analyzed in 20 cases with EOPE and 20 controls. All fetuses were male. The maternal serum cffDNA level was assessed by amplification of the Y chromosome specific gene. Correlations between the variables were examined. (Logged) cffDNA in EOPE (median, 3.08; interquartile range, 2.93-3.68) was higher than controls (median, 1.79; interquartile range, 1.46-2.53). The increased level of (logged) cffDNA was correlated significantly with the increased human chorionic gonadotropin (HCG) level (r = 0.628, p < 0.001). Significant reciprocal correlations between cffDNA and babies' birth weight as well as gestation weeks at delivery were noted (r = -0.516, p = 0.001; r = -0.623, p < 0.001, respectively). The sensitivity and specificity of cffDNA to discriminate between the EOPE cases and the controls were 90% and 85%, respectively. CffDNA is a potential marker for EOPE, which had a significant reciprocal correlation with babies' birth weight and gestation weeks at delivery. Moreover, it may help in indicating the underlying hypoxic condition in the placenta.

RASSF1A in maternal plasma as a molecular marker of preeclampsia

OBJECTIVES

This study aimed to quantitate cell free (cf) and cell free fetal (cff) DNA in maternal plasma by determining RASSF1A levels before and after enzyme digestion in women who subsequently developed preeclampsia (PE) and compare them with uncomplicated pregnancies.

METHODS

Twenty-four samples from pregnant women who developed PE and 48 samples from women with uncomplicated pregnancies were analysed. Blood samples were obtained at 11-13 weeks. cfDNA was determined by quantifying RASSF1A using qRT-PCR. A second qRT-PCR was performed following methylation-sensitive enzyme digestion by BstUI, to quantitate hypermethylated RASSF1A sequences of fetal origin. ACTB gene was used as control to confirm complete enzyme digestion.

RESULTS

cfDNA and cffDNA levels were significantly increased in women who developed PE as compared with uncomplicated pregnancies (median cfDNA: 9402 vs 2698, median cffDNA: 934.5 vs 62, respectively). Following operating characteristic curve analysis, cut-off values of 7486 Εq/mL for cfDNA and 512 Εq/mL for cffDNA were chosen, which provided a sensitivity of 75% and 100% and specificity of 98% and 100%, respectively, to identify women at risk for PE.

CONCLUSIONS

The study demonstrates potential use of cfDNA and cffDNA in maternal plasma as markers for the early prediction of women at risk for PE.

Maternal plasma cell-free fetal and maternal DNA at 11-13 weeks' gestation: relation to fetal and maternal characteristics and pregnancy outcomes

OBJECTIVE

To examine the possible relationship between maternal and fetal characteristics and pregnancy outcomes on fetal and maternal cell-free (cf) DNA in maternal plasma at 11-13 weeks' gestation.

METHODS

cfDNA was extracted from maternal plasma of 1,949 singleton pregnancies and chromosome-selective sequencing was used to determine the proportion of cfDNA and total cfDNA counts which was of fetal and maternal origin. Multivariate regression analysis was used to determine whether specific maternal and fetal characteristics and pregnancy complications, such as preeclampsia (PE), early spontaneous preterm birth (SPB) and delivery of small for gestational age (SGA) neonates, were significant predictors of fetal and maternal cfDNA in maternal plasma.

RESULTS

The fetal and maternal cfDNA plasma concentration increased with serum pregnancy-associated plasma protein-A and free β-human chorionic gonadotropin level, was higher in women of Afro-Caribbean and East-Asian racial origin than in Caucasians, and lower in smokers, but it was not significantly altered in pregnancies complicated by PE, SPB or SGA. The fetal cfDNA level was inversely related to maternal weight and uterine artery pulsatility index, and maternal cfDNA increased with maternal weight.

CONCLUSIONS

The fetal and maternal cfDNA level in maternal plasma is affected by maternal and fetal characteristics, but it is not altered in pregnancy complications.

Association of fetal-derived hypermethylated RASSF1A concentration in placenta-mediated pregnancy complications

OBJECTIVES

To assess whether fetal-derived hypermethylated RASSF1A concentrations in maternal plasma during pregnancy are altered in pregnancies associated with placental dysfunction manifested by intrauterine growth restriction (IUGR), preeclampsia (PE), or placental previa (PP) and whether this alteration can be detected in susceptible subjects before the onset of clinical disease.

METHODS

We performed a real-time quantitative polymerase chain reaction to quantify RASSF1A concentrations before and after methylation-sensitive restriction digestion in maternal plasma at 7-41 gestational weeks of normal pregnancies (n = 161), IUGR (n = 43), PE (n = 22), PP (n = 14) and non-pregnant women (n = 20).

RESULTS

A positive correlation was observed between fetal-derived hypermethylated RASSF1A concentration and gestational age for all study groups (r = 0.624, p < 0.001 for IUGR; r = 0.381, p = 0.042 for PE; r = 0.697, p < 0.001 for PP; r = 0.560, p < 0.001 for controls). The concentration of hypermethylated RASSF1A was relatively high at 7-14 gestational weeks in all patient groups. Hypermethylated RASSF1A concentration at 15-28 weeks was significantly higher in patients who subsequently developed IUGR (p = 0.002), PE (p < 0.001) or PP (p < 0.001) than in controls.

CONCLUSION

We first demonstrated increased concentration of fetal-derived hypermethylated RASSF1A sequences according to advancing gestation and before the onset of the clinical manifestation of pregnancy complications secondary to placental dysfunction, such as IUGR, PE and PP. Hypermethylated RASSF1A in maternal plasma may be useful as a potential biomarker to detect placental-mediated pregnancy complications, regardless of fetal gender and polymorphism.

Cell-free fetal DNA and adverse outcome in low risk pregnancies

OBJECTIVE

To analyze in a large prospective cohort study of low risk pregnancies whether cell-free fetal (cff) DNA in maternal plasma of the second trimester might be associated with the development of preeclampsia, preterm delivery, and small for gestational age.

STUDY DESIGN

A subset of a large prospective cohort study in serological RhD negative pregnant women with RHD positive fetuses was used. Cff DNA was determined through the detection of RHD specific sequences with real-time PCR.

RESULTS

In 611 pregnancies, rates of 7.2% preeclampsia, 1.6% preterm birth ≤32, 2.9% ≤34, and 12.4% ≤37 weeks of gestation, 5.7% of small for gestational age <5th percentile, and 8.2% <10th percentile were observed. For none of these risk groups an association with cff DNA could be established.

CONCLUSION

Cff DNA in maternal plasma of the second trimester was not found to be a marker for an adverse pregnancy outcome in low risk pregnancies.

Cell-free fetal nucleic acids as prenatal biomarkers

INTRODUCTION

Cell-free fetal nucleic acids in maternal plasma or serum have become important tools in the pursuance of new methods for non-invasive prenatal diagnosis, such as the determination of fetal blood groups and fetal gender. During these pioneering explorations, elevations in the concentration of these new-found biological analytes were noted in several pregnancy-related disorders, including preterm labor, pre-eclampsia and malimplantation. As these elevations appeared to occur before onset of clinical symptoms, it was proposed that such analyses might assist in screening for at-risk pregnancies. A major problem with these early studies is that they relied on the quantitation of Y-chromosome-specific gene sequences, and as such could be applied only in those cases where the fetus was male. Recent developments that might permit gender-independent analysis include epigenetic markers, as well as the analysis of cell-free placentally derived mRNA species.

AREAS COVERED

This article focuses specifically on prognostic markers, which enable at-risk pregnancies to be identified, allowing the modification of pregnancy management and in turn improvement of pregnancy outcome. The authors also provide their opinion on the progress and future challenges that lie ahead.

EXPERT OPINION

Accurate quantification of fetal nucleic acids and the specificity of these elevations for particular disorders remain controversial issues. Regarding the multifactorial etiology of some pregnancy disorders, the use of fetal nucleic acids as prenatal markers is restricted to well-defined high-risk groups.

First-trimester maternal plasma cell-free fetal DNA and preeclampsia

OBJECTIVE

The purpose of this study was to determine whether, in pregnancies that experience preeclampsia, plasma cell-free fetal DNA (cffDNA) at 11-13 weeks of gestation is increased and whether this increase is related to the uterine artery pulsatility index (PI).

STUDY DESIGN

Plasma cffDNA and uterine artery PI were measured in 44 cases with preeclampsia, which included 11 cases that required delivery at <34 weeks of gestation and 176 normal control subjects. All fetuses were male, and cffDNA was assessed by amplification of the DYS14 gene. The association between cffDNA and uterine artery PI was assessed by regression analysis.

RESULTS

Median cffDNA was higher in early preeclampsia (median, 95.5 genome equivalents/mL; interquartile range, 72.7-140.9 genome equivalents/mL), but not late preeclampsia (median, 50.8 genome equivalents/mL; interquartile range, 25.0-103.8 genome equivalents/mL), than control subjects (median, 51.5 genome equivalents/mL; interquartile range, 31.1-84.9 genome equivalents/mL). There was a significant association between cffDNA and uterine artery PI (P = .038) but not in the control subjects (P = .174).

CONCLUSION

The increase in plasma cffDNA in pregnancies that experience preeclampsia is associated with the degree of impairment in placental perfusion.

Membrane protected apoptotic trophoblast microparticles contain nucleic acids: relevance to preeclampsia

Microparticles (MPs) that circulate in blood may be a source of DNA for molecular analyses, including prenatal genetic diagnoses. Because MPs are heterogeneous in nature, however, further characterization is important before use in clinical settings. One key question is whether DNA is either bound to aggregates of blood proteins and lipid micelles or intrinsically associated with MPs from dying cells. To test the latter hypothesis, we asked whether MPs derived in vitro from dying cells were similar to those in maternal plasma. JEG-3 cells model extravillous trophoblasts, which predominate during the first trimester of pregnancy when prenatal diagnosis is most relevant. MPs were derived from apoptosis and increased over 48 hours. Compared with necrotic MPs, DNA in apoptotic MPs was more fragmented and resistant to plasma DNases. Membrane-specific dyes indicated that apoptotic MPs had more membranous material, which protects nucleic acids, including RNA. Flow cytometry showed that MPs derived from dying cells displayed light scatter and DNA staining similar to MPs found in maternal plasma. Quantification of maternal MPs using characteristics defined by MPs generated in vitro revealed a significant increase of DNA(+) MPs in the plasma of women with preeclampsia compared with plasma from women with normal pregnancies. Apoptotic MPs are therefore a likely source of stable DNA that could be enriched for both early genetic diagnosis and monitoring of pathological pregnancies.

Prediction and perinatal outcomes of fetal growth restriction

Assessment of fetal growth and wellbeing is one of the major purposes of antenatal care. Some fetuses have smaller than expected growth in utero and while some of these fetuses are constitutionally small, others have failed to meet their growth potential, that is they are growth restricted. While severe growth restriction is uncommon, the consequences of it being undetected may include perinatal death or severe morbidity. It is, therefore, important to have strategies in place to detect the fetus at risk of growth restriction. These would include an assessment of 'prior risk' from maternal history and examination combined with the results of biochemical and ultrasound investigations, the most promising of which are uterine artery Doppler and biochemistry. We discuss some of the factors to consider when stratifying the obstetric population into degrees of likelihood for growth restriction, and discuss aspects of the management and outcome of pregnancies complicated by growth restriction.