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

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.

Low fetal fraction and adverse pregnancy outcomes- systematic review of the literature and metanalysis

PURPOSE

While cell-free DNA (cfDNA) screening has emerged as a screening modality for common aneuploidies, further research and several publications over the past decade suggested some correlation between the low concentrations of cfDNA and a number of pregnancy-related complications. The primary goal of this systematic review and meta-analysis was to assess the potential value of low-ff levels in the prediction of subsequent PE/PIH, GDM, SGA/FGR, and PTB. The meta-analysis results aim at summarizing the currently available literature data and determining the clinical relevance of this biochemical marker and the potential necessity for additional investigation of its utility in complications other than the detection of common aneuploidies.

METHODS

This systematic review and meta-analysis was designed according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. It included all observational studies that reported low -ff levels after the performance of non-invasive prenatal testing (NIPT) as part of the screening for chromosomal abnormalities and their association with adverse pregnancy outcomes, namely the subsequent development of hypertensive disorders of pregnancy, gestational diabetes, preterm birth, and the detection of small for gestational age fetuses or growth-restricted fetuses. The Medline (1966-2041), Scopus (2004-2024), Clinicaltrials.gov (2008-2024), EMBASE (1980-2024), Cochrane Central Register of Controlled Trials CENTRAL (1999-2024) and Google Scholar (2004-2024) databases were used in our primary search along with the reference lists of electronically retrieved full-text papers. The date of our last search was set at February 29, 2024.

RESULTS

Our search identified 128 potentially relevant studies and,overall, 8 studies were included in the present systematic review that enrolled a total of 72,507 patients. Low ff of cfDNA cfDNA was positively associated with HDP (OR 1.66, 95% CI 1.34, 2.06, I-square test: 56%). Low ff of cfDNA was positively associated with GDM (OR 1.27, 95% CI 1.03, 1.56, I-square test: 76%). Furthermore, low ff levels were positively associated with SGA/FGR (OR 1.63, 95% CI 1.32, 2.03, I-square test: 0%). Low ff levels were positively correlated with the risk for PTB but the association did not manage to reach a statistical significant level (OR 1.22, 95% CI 0.89, 1.67, I-square test: 66%).

CONCLUSION

Our study suggests that low ff is associated with increased risk of adverse perinatal outcomes, including PE/PIH, GDM, and SGA/FGR. However, the relationship between ff and PTB remains unclear due to conflicting evidence. It should be emphasized that further research is needed to reveal the underlying mechanisms behind the association of low ff with adverse pregnancy outcomes and explore its potential role in an overall prenatal screening, which could potentially not be limited to detecting aneuploidies.

The Association between Low Fetal Fraction of Non-Invasive Prenatal Testing and Adverse Pregnancy Outcomes for Placental Compromise

(1) Background: Non-invasive prenatal testing (NIPT) is a screening test for fetal aneuploidy using cell-free fetal DNA. The fetal fragments (FF) of cell-free DNA (cfDNA) are derived from apoptotic trophoblast of the placenta. The level of fetal cfDNA is known to be influenced by gestational age, multiple pregnancies, maternal weight, and height. (2) Methods: This study is a single-center retrospective observational study which examines the relationship between the fetal fraction (FF) of cell-free DNA in non-invasive prenatal testing (NIPT) and adverse pregnancy outcomes in singleton pregnancies. A total of 1393 samples were collected between 10 weeks and 6 days, and 25 weeks and 3 days of gestation. (3) Results: Hypertensive disease of pregnancy (HDP) occurred more frequently in the low FF group than the normal FF group (5.17% vs. 1.91%, p = 0.001). Although the rates of small for gestational age (SGA) and placental abruption did not significantly differ between groups, the composite outcome was significantly higher in the low FF group (7.76% vs. 3.64%, p = 0.002). Furthermore, women who later experienced complications such as HDP or gestational diabetes mellitus (GDM) had significantly lower plasma FF levels compared to those without complications (p < 0.001). After adjustments, the low FF group exhibited a significantly higher likelihood of placental compromise (adjusted odds ratio: 1.946). (4) Conclusions: Low FF in NIPT during the first and early second trimesters is associated with adverse pregnancy outcomes, particularly HDP, suggesting its potential as a predictive marker for such outcomes.

Cell‑free fetal DNA at 11‑13 weeks of gestation is not altered in complicated pregnancies

Non-invasive maternal cell-free fetal DNA (cffDNA) is a promising biomarker for screening common genetic syndromes. Alterations in the expression levels of cffDNA in the maternal circulation have been demonstrated in abnormal pregnancies. However, the results are conflicting. The present study aimed to investigate whether cffDNA levels are associated with pregnancy complications. The study group comprised pregnant women who presented with pregnancy complications, such as preterm birth, gestational hypertension, intrauterine growth retardation, gestational diabetes, polyhydramnios, oligohydramnios, vaginal bleeding and placental abruption. The control group comprised women who had a normal pregnancy course. Blood samples were obtained from 500 pregnant women between 11-13 weeks of gestation. cffDNA was amplified, sequenced and analyzed using the next-generation aneuploidy test of a Panorama-Natera kit. Nuchal translucency (NT) thickness as well as pregnancy associated plasma protein-A (PAPP-A) and β-human chorionic gonadotropin (β-hCG) levels were also assessed. Statistical analysis was performed in 494 out of the 500 samples collected with SPSS v.26 using non-parametric methods. The parameters were normalized by the multiples of median (MoM) method. The expression levels of PAPP-A, β-hCG, and the NT mean MoM values were significantly different between the study and control groups (P=0.005, P<0.001 and P=0.007, respectively). However, the expression levels of cffDNA and the mean MoM values were not significantly different between these two groups (P=0.687). The findings of the present study support the conclusion that cffDNA expression is not altered in a series of pregnancy complications. The prognostic value of cffDNA in predicting adverse pregnancy outcomes requires further investigation.

Prevention of spontaneous preterm delivery – an update on where we are today

Spontaneous preterm birth (delivery before 37 completed weeks) is the single most important cause of perinatal morbidity and mortality. The rate is increasing world-wide with a great disparity between low, middle and high income countries. It has been estimated that the cost of neonatal care for preterm babies is more than 4 times that of a term neonate admitted into the neonatal care. Furthermore, there are high costs associated with long-term morbidity in those who survive the neonatal period. Interventions to stop delivery once preterm labor starts are largely ineffective hence the best approach to reducing the rate and consequences is prevention. This is either primary (reducing or minimizing factors associated with preterm birth prior to and during pregnancy) or secondary - identification and amelioration (if possible) of factors in pregnancy that are associated with preterm labor. In the first category are optimizing maternal weight, promoting healthy nutrition, smoking cessation, birth spacing, avoidance of adolescent pregnancies and screening for and controlling various medical disorders as well as infections prior to pregnancy. Strategies in pregnancy, include early booking for prenatal care, screening and managing medical disorders and their complications, and identifying predisposing factors to preterm labor such as shortening of the cervix and timely instituting progesterone prophylaxis or cervical cerclage where appropriate. The use of biomarkers such as oncofetal fibronectin, placental alpha-macroglobulin-1 and IGFBP-1 where cervical screening is not available or to diagnosis PPROM would identify those that require close monitoring and allow the institution of antibiotics especially where infection is considered a predisposing factor. Irrespective of the approach to prevention, timing the administration of corticosteroids and where necessary tocolysis and magnesium sulfate are associated with an improved outcome. The role of genetics, infections and probiotics and how these emerging dimensions help in the diagnosis of preterm birth and consequently prevention are exciting and hopefully may identify sub-populations for targeted strategies.

Cell free DNA screening for fetal aneuploidy in Ireland: An observational study of outcomes following insufficient fetal fraction

OBJECTIVES

To determine maternal factors associated with low fetal fraction (FF). To determine the proportion of women who receive a result from repeat non-invasive prenatal testing (NIPT) testing. To identify any significant associations between pregnancy interventions or outcomes and low FF.

STUDY DESIGN

Retrospective observational study of 4465 women undergoing antenatal screening by targeted cell free DNA (cfDNA) testing at an Irish tertiary maternity hospital between January 2017 and December 2022. Patients who failed to obtain a result after the first NIPT were analyzed in two cohorts; those who received a result on a repeat sample and those who failed to ever achieve a result despite a second, third or fourth cfDNA test.

RESULTS

Risk of insufficient FF significantly increased with elevated maternal BMI (OR 1.07; 95% CI 1.01-1.13, p = 0.03) and in-vitro fertilization (IVF) (OR 3.4; 95% CI 1.19-9.4, p = 0.02). Women with no result were more likely to have diagnostic invasive testing (p < 0.01), but had no increased risk of aneuploidy. Repeated failed NIPT attempts due to low FF were significantly associated with the subsequent development of hypertensive diseases of pregnancy (p = 0.03). Greater than 70% of patients who were unsuccessful in a first or second attempt at NIPT due to low FF yielded a result following a second or third sample.

CONCLUSIONS

High BMI and IVF conceptions are greater contributors to low FF than fetal aneuploidy. Repeating NIPT yields a result in greater than 70% of cases. WHAT'S ALREADY KNOWN ABOUT THIS TOPIC?: Fetal fraction (FF) in prenatal cfDNA testing is influenced by maternal and pregnancy factors including body mass index (BMI) and IVF. Low FF has been associated with adverse pregnancy outcomes including fetal aneuploidy and hypertensive diseases of pregnancy. WHAT DOES THIS STUDY ADD?: In a large Irish population, increasing maternal BMI and in-vitro fertilization are the most significant contributors to repeated test failures due to low FF. Greater than 70% of patients with test failure due to low FF will receive a result on 2nd and 3rd NIPT attempts. Patients with no result from NIPT were more likely to undergo diagnostic invasive testing but the risk of aneuploidy was not significantly increased.

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.

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.

Cell-free DNA Screening for Aneuploidy

Cell-free DNA (cfDNA) screening has high detection for the common fetal autosomal aneuploidies, but is not diagnostic. The positive predictive value should be utilized in counseling after a positive cell-free DNA screen, and diagnostic testing should be offered for confirmation. cfDNA screening does not report a result in ~3% of cases; nonreportable results indicate an increased risk for aneuploidy and some adverse perinatal outcomes. False-positive cfDNA screening occurs due to confined placental mosaicism, maternal copy number variants, mosaicism, and cancer. Pretest education and counseling should be provided with emphasis on the potential benefits, risks, and limitations before cfDNA screening.

Association between the first and second trimester cell free DNA fetal fraction and spontaneous preterm birth

OBJECTIVE

To evaluate whether the fetal fraction of cell-free DNA at the first and second trimesters is associated with spontaneous preterm birth.

METHODS

This was a retrospective cohort study with singleton pregnancies who underwent noninvasive prenatal testing. According to pregnancy outcome, eligible patients were divided into a delivery group ≥37 weeks of pregnancy (term group) and <37 weeks of pregnancy (spontaneous preterm group). Stepwise linear regression was used to identify maternal characteristics associated with the fetal fraction of cell-free DNA. Logistic regression analysis was performed to evaluate the association between the fetal fraction of cell-free DNA and spontaneous preterm birth, adjusted for confounding factors.

RESULTS

14,020 cases were included in the study, 13292 cases (94.81%) in the term group and 728 cases (5.19%) in the spontaneous preterm group. The cell-free fraction of fetal DNA was inversely correlated with maternal age and body mass index. Positively correlated with gestational age, fertility, and assisted reproductive technology. After adjusting for the covariates, logistic regression analysis revealed no statistically significant association between the fetal fraction of cell-free DNA and spontaneous preterm birth.

CONCLUSION

In our original study, we found no association between the fetal fraction on NIPT and subsequent spontaneous preterm birth.

Position statement from the International Society for Prenatal Diagnosis on the use of non-invasive prenatal testing for the detection of fetal chromosomal conditions in singleton pregnancies

What is already known about this topic?

What does this study add?

Circulating biomarkers associated with placental dysfunction and their utility for predicting fetal growth restriction

Fetal growth restriction (FGR) leading to low birth weight (LBW) is a major cause of neonatal morbidity and mortality worldwide. Normal placental development involves a series of highly regulated processes involving a multitude of hormones, transcription factors, and cell lineages. Failure to achieve this leads to placental dysfunction and related placental diseases such as pre-clampsia and FGR. Early recognition of at-risk pregnancies is important because careful maternal and fetal surveillance can potentially prevent adverse maternal and perinatal outcomes by judicious pregnancy surveillance and careful timing of birth. Given the association between a variety of circulating maternal biomarkers, adverse pregnancy, and perinatal outcomes, screening tests based on these biomarkers, incorporating maternal characteristics, fetal biophysical or circulatory variables have been developed. However, their clinical utility has yet to be proven. Of the current biomarkers, placental growth factor and soluble fms-like tyrosine kinase 1 appear to have the most promise for placental dysfunction and predictive utility for FGR.

Associations of circulating cell-free DNA, C-reactive protein, and cardiometabolic risk among low-active smokers with elevated depressive symptoms

Background and aims

Cell-free DNA (cfDNA) is elevated in several disease states. Metabolic syndrome is a constellation of factors associated with poor cardiometabolic outcomes. This study examined associations of cfDNA from the nucleus (cf-nDNA) and mitochondria (cf-mtDNA), C-reactive protein (CRP), and metabolic syndrome risk, in low-active smokers with depressive symptoms.

Methods

Participants (N = 109; mean age 47) self-reported medical history. Physical activity was determined by accelerometry and anthropometrics were measured. Blood was collected and analyzed for cf-nDNA, cf-mtDNA, CRP, triglycerides, high-density lipoprotein, hemoglobin A1c. A continuous metabolic syndrome composite risk score was calculated. Relationships of cf-nDNA, cf-mtDNA, CRP, and cardiometabolic risk were examined with correlations and linear regression.

Results

CRP and cf-nDNA were significantly associated with metabolic syndrome risk (r = .39 and r = .31, respectively), cf-mtDNA was not (r = .01). In a linear regression, CRP and cf-nDNA significantly predicted the metabolic syndrome risk score, findings that remained significant controlling for age, gender, nicotine dependence, and physical activity.

Conclusions

Associations of cf-nDNA with both CRP and metabolic risk suggest a role for cf-nDNA in inflammatory processes associated with metabolic syndrome. The negative findings for cf-mtDNA suggest distinct roles for cf-nDNA and cf-mtDNA in these processes.

The association between fetal fraction and pregnancy-related complications among Chinese population

To examine the association of fetal fraction with a wide spectrum of pregnancy-related complications among Chinese population, we carried out a single-institution retrospective cohort study of women with negative Noninvasive prenatal testing (NIPT) results and singleton pregnancies between May 2018 and May 2020. Indicators of pregnancy-related complications were examined individually, including preterm birth, low birth weight, hypertensive disorders of pregnancy, gestational diabetes, oligohydramnios and intrahepatic cholestasis. We evaluated disease odds ratios (ORs) and 95% confidence intervals (CIs), after controlling for potential confounders including body mass index (BMI), maternal age and gestational week at NIPT. A total of 3534 women were included in our analyses. Women with fetal fraction<15.15% had increased risk of gestational hypertension (OR 4.41, CI [1.65, 12.45]) and oligohydramnios (OR 2.26, CI [1.33, 3.80]) compared to women with fetal fraction≥15.15%. No significant associations with fetal fraction were found for preterm birth, low birth weight, gestational diabetes, and intrahepatic cholestasis. In Summary, fetal fraction is inversely associated with the risk of gestational hypertension and oligohydramnios.

Is there a maternal blood biomarker that can predict spontaneous preterm birth prior to labour onset? A systematic review

Introduction

The ability to predict spontaneous preterm birth (sPTB) prior to labour onset is a challenge, and it is currently unclear which biomarker(s), may be potentially predictive of sPTB, and whether their predictive power has any utility. A systematic review was conducted to identify maternal blood biomarkers of sPTB.

Methods

This study was conducted according to PRISMA protocol for systematic reviews. Four databases (MEDLINE, EMBASE, CINAHL, Scopus) were searched up to September 2021 using search terms: “preterm labor”, “biomarker” and “blood OR serum OR plasma”. Studies assessing blood biomarkers prior to labour onset against the outcome sPTB were eligible for inclusion. Risk of bias was assessed based on the Newcastle Ottawa scale. Increased odds of sPTB associated with maternal blood biomarkers, as reported by odds ratios (OR), or predictive scores were synthesized. This review was not prospectively registered.

Results

Seventy-seven primary research articles met the inclusion criteria, reporting 278 unique markers significantly associated with and/or predictive of sPTB in at least one study. The most frequently investigated biomarkers were those measured during maternal serum screen tests for aneuploidy, or inflammatory cytokines, though no single biomarker was clearly predictive of sPTB based on the synthesized evidence. Immune and signaling pathways were enriched within the set of biomarkers and both at the level of protein and gene expression.

Conclusion

There is currently no known predictive biomarker for sPTB. Inflammatory and immune biomarkers show promise, but positive reporting bias limits the utility of results. The biomarkers identified may be more predictive in multi-marker models instead of as single predictors. Omics-style studies provide promising avenues for the identification of novel (and multiple) biomarkers. This will require larger studies with adequate power, with consideration of gestational age and the heterogeneity of sPTB to identify a set of biomarkers predictive of sPTB.

Factors Affecting the Fetal Fraction in Noninvasive Prenatal Screening: A Review

A paradigm shift in noninvasive prenatal screening has been made with the discovery of cell-free fetal DNA in maternal plasma. Noninvasive prenatal screening is primarily used to screen for fetal aneuploidies, and has been used globally. Fetal fraction, an important parameter in the analysis of noninvasive prenatal screening results, is the proportion of fetal cell-free DNA present in the total maternal plasma cell-free DNA. It combines biological factors and bioinformatics algorithms to interpret noninvasive prenatal screening results and is an integral part of quality control. Maternal and fetal factors may influence fetal fraction. To date, there is no broad consensus on the factors that affect fetal fraction. There are many different approaches to evaluate this parameter, each with its advantages and disadvantages. Different fetal fraction calculation methods may be used in different testing platforms or laboratories. This review includes numerous publications that focused on the understanding of the significance, influencing factors, and interpretation of fetal fraction to provide a deeper understanding of this parameter.

Single-molecule sequencing reveals a large population of long cell-free DNA molecules in maternal plasma

In the field of circulating cell-free DNA, most of the studies have focused on short DNA molecules (e.g., <500 bp). The existence of long cell-free DNA molecules has been poorly explored. In this study, we demonstrated that single-molecule real-time sequencing allowed us to detect and analyze a substantial proportion of long DNA molecules from both fetal and maternal sources in maternal plasma. Such molecules were beyond the size detection limits of short-read sequencing technologies. The proportions of long cell-free DNA molecules in maternal plasma over 500 bp were 15.5%, 19.8%, and 32.3% for the first, second, and third trimesters, respectively. The longest fetal-derived plasma DNA molecule observed was 23,635 bp. Long plasma DNA molecules demonstrated predominance of A or G 5' fragment ends. Pregnancies with preeclampsia demonstrated a reduction in long maternal plasma DNA molecules, reduced frequencies for selected 5' 4-mer end motifs ending with G or A, and increased frequencies for selected motifs ending with T or C. Finally, we have developed an approach that employs the analysis of methylation patterns of the series of CpG sites on a long DNA molecule for determining its tissue origin. This approach achieved an area under the curve of 0.88 in differentiating between fetal and maternal plasma DNA molecules, enabling the determination of maternal inheritance and recombination events in the fetal genome. This work opens up potential clinical utilities of long cell-free DNA analysis in maternal plasma including noninvasive prenatal testing of monogenic diseases and detection/monitoring of pregnancy-associated disorders such as preeclampsia.

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.

Fetal fraction of cell free DNA in screening for hypertensive disorders at 11-13 weeks

OBJECTIVE

To investigate whether first-trimester maternal plasma fetal fraction is altered in women that subsequently develop preeclampsia (PE) or gestational hypertension (GH) and to examine its potential value in improving the performance of screening for PE and GH by maternal factors and maternal serum pregnancy associated plasma protein-A (PAPP-A), mean arterial pressure (MAP) and uterine artery pulsatility index (UtA-PI).

METHODS

The study population of 10,131 pregnancies undergoing cell free fetal DNA testing at 11-13 weeks' gestation included 91 (0.9%) cases with preterm-PE, 222 (2.2%) cases with term-PE, 360 (3.6%) with GH and 9,458 (93.4%) cases unaffected by hypertensive disorders. Maternal plasma fetal fraction levels were expressed as multiples of the median (MoM) after adjustment for maternal factors and crown-rump length. The performance of screening for preterm-PE, term PE and GH by maternal factors and MoM values of fetal fraction, PAPP-A, UtA-PI and MAP was evaluated by receiver operating characteristic (ROC) curves.

RESULTS

The median fetal fraction MoM was significantly lower in the preterm-PE (0.825; IQR 0.689-1.115 MoM, p < .001), term-PE (0.946; IQR 0.728-1.211 MoM, p = .028) and GH (0.928; IQR 0.711-1.182 MoM, p < .001) groups than in the unaffected group (1.002; IQR 0.785-1.251 MoM). However, the performance of screening for PE or GH by maternal factors alone or by maternal factors and PAPP-A, UtA-PI and MAP was not significantly improved by the addition of fetal fraction.

CONCLUSIONS

First trimester maternal plasma fetal fraction is not useful in screening for hypertensive disorders of pregnancy.

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.

Association between Levels of Total Cell-Free DNA and Development of Preeclampsia-A Literature Review

Objectives  The aim of the study is to synthesize the evidence and evaluate the total cell-free deoxyribonucleic (cfDNA) associated with the prediction of preeclampsia (PE). Total cfDNA is constituted by both cell-free fetal DNA (cffDNA) originated mainly from the placenta, and maternal cfDNA derived from maternal leukocytes. Methods  A systematic review was conducted by searching PubMed and Medline. Literature reporting levels of total cfDNA in the development of PE was included. Studies that only reported cffDNA, but no cfDNA concentrations were not included in this review. Results  Eight studies were included. Seven reported values of cfDNA in PE patients, regardless of early or late onset PE, six of which demonstrated a significant increase of cfDNA in patients who subsequently developed PE. Seven studies evaluated cfDNA levels in the first trimester, six of which showed significant increase of cfDNA concentrations in women who later developed PE. Five studies investigated cfDNA levels in the second trimester, all presenting increased total cfDNA levels in the PE group compared with normal controls. Conclusion  Total cfDNA may play a role as a biochemical marker of PE, compared with fetal cfDNA. Large prospective studies with homogeneous populations and standardized methodology are needed to further confirm its predictive value.

Non-Invasive Prenatal Testing: Current Perspectives and Future Challenges

Fetal aneuploidies are among the most common causes of miscarriages, perinatal mortality and neurodevelopmental impairment. During the last 70 years, many efforts have been made in order to improve prenatal diagnosis and prenatal screening of these conditions. Recently, the use of cell-free fetal DNA (cff-DNA) testing has been increasingly used in different countries, representing an opportunity for non-invasive prenatal screening of pregnant women. The aim of this narrative review is to describe the state of the art and the main strengths and limitations of this test for prenatal screening of fetal aneuploidies.

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.

Association between cell-free DNA fetal fraction and gestational diabetes

OBJECTIVE

To determine the association between cell-free DNA (cfDNA) fetal fraction and gestational diabetes (GDM) in a cohort of women presenting for cfDNA screening for fetal aneuploidy.

METHODS

A retrospective cohort study of women with singleton pregnancies who had cfDNA screening at a single institution at 10 to 20 weeks gestation between October 2011 and October 2017. Fetal fractions were adjusted for gestational age (GA) using multiples of the median (MoM). Multivariable logistic regression was used to estimate the odds ratio (OR) of GDM controlling for potential confounders.

RESULTS

Two thousand six hundred twenty-three pregnancies met criteria. Women with GDM had a lower fetal fraction (0.93 MoM vs. 1.05 MoM, P = .002). However, the association between fetal fraction and GDM was not significant after adjusting for body mass index (BMI) [OR 0.84, 95% confidence interval (CI) 0.52-1.36; P = .48]. Since insulin resistance increases at later GAs, separate analysis on women with GA 14 to 20 weeks was performed. Again, the association between fetal fraction and GDM was not significant after adjusting for BMI, (OR 0.81, 95% CI 0.31-2.12; P = .67).

CONCLUSION

Low or high fetal fraction of cfDNA was not associated with GDM. Although fetal fraction was lower among women diagnosed with GDM, this relationship was no longer statistically significant once maternal BMI was taken into account.

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.

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.

Implementation of maternal blood cell-free DNA testing in early screening for aneuploidies

Several externally blinded validation and implementation studies in the last 9 years have shown that it is now possible, through analysis of cell-free (cf) DNA in maternal blood, to effectively detect a high proportion of fetuses affected by trisomies 21, 18, and 13 at a much lower false-positive rate (FPR) than all other existing screening methods. This article is aimed at reviewing technical and clinical considerations for implementing cfDNA testing in routine practice, including methods of analysis, performance of the test, models for clinical implementation, and interpretation of results.

Could high levels of cell-free DNA in maternal blood be associated with maternal health and perinatal outcomes?

The aim of this study was to evaluate the maternal and foetal factors affect higher cell-free DNA (cfDNA) levels and to investigate a possible relationship between high cfDNA levels and adverse perinatal outcomes. From a total of 4594 women who underwent non-invasive prenatal testing from January 2016 to March 2018 in our hospital, 112 women had high levels of cfDNA, which was not appropriate for testing. Maternal characteristics and perinatal outcomes were compared between patients with high levels of cfDNA and normal levels of cfDNA. Patients with high levels of cfDNA had greater risks than patients with normal cfDNA levels of pregnancy complications but no statistically significant difference was found. Patients with high cfDNA levels had higher foetal death rates with a statistically significant difference (9.8% versus 1.8%, p = .024). An increase in foetal death could be expected in patients with increased cfDNA levels; therefore, these patients should be carefully followed up during pregnancy.IMPACT STATEMENTWhat's already known about this topic? Most studies about cfDNA levels are focussed on the foetal fraction. There are new arguments about maternal health and cfDNA. It is known that autoimmune diseases as systemic lupus erythematosus (SLE) and maternal obesity increase cell turnover. There are also clinical studies suggesting a relationship between low molecular weight heparin therapy and the amount of cfDNA.What do the results of this study add? This is the first study evaluating the maternal and foetal biological factors affecting cfDNA concentrations and investigating the possible relationship between high cfDNA levels and adverse perinatal outcomes in patients with high levels of cfDNA compared to patients with normal levels of cfDNA. In the present study, it was found that an increase in foetal death could be expected in patients with higher cfDNA levels.What are the implications of these findings for clinical practice and/or further research? If potential effects and underlying causes of increased cfDNA could be explained, cfDNA might be used as a biomarker for adverse perinatal outcomes.

Association between fetal fraction at the second trimester and subsequent spontaneous preterm birth

OBJECTIVE

To evaluate the association between the fetal fraction of cell-free DNA at the second trimester and subsequent spontaneous preterm birth.

METHODS

In this retrospective cohort study, data were collected from women with singleton pregnancies who underwent noninvasive prenatal testing at 14 to 25 weeks of gestation. The eligible patients were classified into three groups according to pregnancy outcome: birth at ≥37 weeks of gestation (term group), delivery at <34 weeks of gestation (early spontaneous preterm), and delivery at 34⁺⁰ to 36⁺⁶  weeks of gestation (late spontaneous preterm). Stepwise linear regression was performed to determine the maternal characteristics associated with the fetal fraction of cell-free DNA. Logistic regression was used to determine the relationship between the fetal fraction of cell-free DNA and pregnancy outcomes by adjusting for history of preterm birth.

RESULTS

A total of 8129 singleton pregnancies met the recruitment criteria. Among them, 7790 (95.83%) were in the term group, 284 (3.49%) were in the late spontaneous preterm group, and 55 (0.68%) were in the early spontaneous preterm group. The fetal fraction of cell-free DNA was negatively correlated with body mass index, maternal age, nulliparity, and history of spontaneous preterm birth; positively correlated with gestational age; and not correlated with assisted reproduction or surface antigen of hepatitis B virus (HBsAg) positivity. After adjusting for history of preterm birth, a logistic regression analysis demonstrated no statistically significant associations between the fetal fraction of cell-free DNA and spontaneous preterm birth in any of the preterm groups (<34 weeks, 34⁺⁰ to 36⁺⁶  weeks, and <37 weeks).

CONCLUSION

Our preliminary study found no relationship between the fetal fraction on NIPT at the second trimester and subsequent spontaneous preterm birth.

[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.

Cell-Free Fetal DNA in the Early and Late First Trimester

OBJECTIVE

The aim of this work was to investigate the association between maternal and fetal characteristics and the fetal fraction at 8-14 weeks' gestation, with emphasis on the change in the fetal fraction upon repeat sampling.

METHOD

One sample for cell-free DNA (cfDNA) testing was collected at the same time as the biochemical markers for combined first trimester screening (visit 1) and another at the nuchal translucency scan (visit 2). Chromosome-selective cfDNA analysis was performed on frozen plasma.

RESULTS

Overall, 321 women were included at visit 1, and 307 had a repeat blood sampling. A fetal fraction was obtained in 532 samples (238 samples with repeat fetal fraction). The fetal fraction decreased with maternal BMI (p < 0.001), was lower in Asian women (p = 0.03), and increased with β-hCG levels (p < 0.001) and gestational age (p = 0.04). Before 10 weeks' gestation, the fetal fraction was lower (p = 0.02), as was the probability of a sufficient fetal fraction (p = 0.03) after adjustment for maternal BMI. Asian women had a higher increase in fetal fraction upon repeat sampling (p < 0.001).

CONCLUSION

Before 10 weeks' gestation, the fetal fraction is significantly lower but seems to increase more rapidly compared to later gestations. Presently, combined first trimester screening with cfDNA testing should not include samples before 10 weeks' gestation.

First-trimester screening for trisomies by cfDNA testing of maternal blood in singleton and twin pregnancies: factors affecting test failure

OBJECTIVE

To examine factors affecting the rate of failure to obtain a result from cell-free DNA (cfDNA) testing of maternal blood for fetal trisomies 21, 18 and 13 in singleton and twin pregnancies in the first trimester.

METHODS

This was a prospective study of 23 495 singleton and 928 twin pregnancies undergoing screening for fetal trisomy by targeted cfDNA testing at 10 + 0 to 14 + 1 weeks' gestation. Multivariate logistic regression analysis was used to determine significant predictors of failure to obtain a result after first sampling.

RESULTS

There was no result from cfDNA testing after first sampling in 3.4% (798/23 495) of singletons, 11.3% (91/806) of dichorionic twins and 4.9% (6/122) of monochorionic twins. Multivariate logistic regression analysis demonstrated that the risk of test failure, first, increased with increasing maternal age (odds ratio (OR), 1.02; 95% CI, 1.01-1.04) and weight (OR, 1.05; 95% CI, 1.04-1.05), decreasing gestational age (OR, 0.85; 95% CI, 0.79-0.91), serum pregnancy-associated plasma protein-A (PAPP-A) multiples of the median (MoM) (OR, 0.56; 95% CI, 0.49-0.65) and free β-human chorionic gonadotropin (β-hCG) MoM (OR, 0.67; 95% CI, 0.60-0.74), second, was higher in women of black (OR, 1.72; 95% CI, 1.33-2.20) and South Asian (OR, 1.99; 95% CI, 1.56-2.52) than those of white racial origin, in dichorionic twin than in singleton pregnancy (OR, 1.75; 95% CI, 1.34-2.26) and in pregnancies conceived by in-vitro fertilization than in those conceived naturally (OR, 3.82; 95% CI, 3.19-4.55) and, third, was lower in parous than in nulliparous women (OR, 0.63; 95% CI, 0.55-0.74).

CONCLUSIONS

Maternal age, weight, racial origin and parity, gestational age, dichorionicity, method of conception and serum levels of free β-hCG and PAPP-A are independent predictors of cfDNA test failure. The risk of test failure is higher in dichorionic twin than in singleton pregnancies, mainly because a higher proportion of twins are conceived by in-vitro fertilization and more of the women are nulliparous. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

The Effect of Maternal Obesity on Placental Cell-Free DNA Release in a Mouse Model

BACKGROUND

The fetal fraction of cell-free DNA (cfDNA) in maternal plasma is decreased in obese women. The underlying mechanism is not well understood. The amount of cfDNA released from the placenta has not been directly examined in maternal obesity.

OBJECTIVE

We sought to quantify release of cfDNA from the placenta and fetal membranes in maternal diet-induced obesity using explant cultures in an established mouse model.

STUDY DESIGN

C57BL6/J females were fed either 60% high-fat diet or 10% fat-matched control diet for 14 weeks prepregnancy and throughout gestation. Placentas and fetal membranes were collected on e18 and randomly allocated to time 0-, 1-, or 6-hour culture times. The CfDNA was isolated from culture media, quantified, and normalized to tissue weight.

RESULTS

Placentas from obese dams released significantly less cfDNA compared to those of lean dams at time 0 (45.8 ± 4.3 ng/mg vs 65.6 ± 7.9 ng/mg, P = .02). Absolute cfDNA levels increased with longer placental culture, with no significant differences between obese and lean dams at 1 and 6 hours. Membranes released significantly less cfDNA than did placentas at every time point.

CONCLUSIONS

Maternal obesity is associated with decreased release of cfDNA from the placenta compared to lean controls immediately after tissue harvest. This may provide an alternative explanation for the lower fetal fraction of cfDNA noted in maternal obesity.

Screening for fetal growth restriction using fetal biometry combined with maternal biomarkers

Fetal growth restriction is a major determinant of perinatal morbidity and mortality. Screening for fetal growth restriction is a key element of prenatal care but it is recognized to be problematic. Screening using clinical risk assessment and targeting ultrasound to high-risk women is the standard of care in the United States and United Kingdom, but the approach is known to have low sensitivity. Systematic reviews of randomized controlled trials do not demonstrate any benefit from universal ultrasound screening for fetal growth restriction in the third trimester, but the evidence base is not strong. Implementation of universal ultrasound screening in low-risk women in France failed to reduce the risk of complications among small-for-gestational-age infants but did appear to cause iatrogenic harm to false positives. One strategy to making progress is to improve screening by developing more sensitive and specific tests with the key goal of differentiating between healthy small fetuses and those that are small through fetal growth restriction. As abnormal placentation is thought to be the major cause of fetal growth restriction, one approach is to combine fetal biometry with an indicator of placental dysfunction. In the past, these indicators were generally ultrasonic measurements, such as Doppler flow velocimetry of the uteroplacental circulation. However, another promising approach is to combine ultrasonic suspicion of small-for-gestational-age infant with a blood test indicating placental dysfunction. Thus far, much of the research on maternal serum biomarkers for fetal growth restriction has involved the secondary analysis of tests performed for other indications, such as fetal aneuploidies. An exemplar of this is pregnancy-associated plasma protein A. This blood test is performed primarily to assess the risk of Down syndrome, but women with low first-trimester levels are now serially scanned in later pregnancy due to associations with placental causes of stillbirth, including fetal growth restriction. The development of "omic" technologies presents a huge opportunity to identify novel biomarkers for fetal growth restriction. The hope is that when such markers are measured alongside ultrasonic fetal biometry, the combination would have strong predictive power for fetal growth restriction and its related complications. However, a series of important methodological considerations in assessing the diagnostic effectiveness of new tests will have to be addressed. The challenge thereafter will be to identify novel disease-modifying interventions, which are the essential partner to an effective screening test to achieve clinically effective population-based screening.

Cell-free fetal DNA and spontaneous preterm birth

Inflammation is known to play a key role in preterm and term parturition. Cell-free fetal DNA (cff-DNA) is present in the maternal circulation and increases with gestational age and some pregnancy complications (e.g. preterm birth, preeclampsia). Microbial DNA and adult cell-free DNA can be pro-inflammatory through DNA-sensing mechanisms such as Toll-like receptor 9 and the Stimulator of Interferon Genes (STING) pathway. However, the pro-inflammatory properties of cff-DNA, and the possible effects of this on pregnancy and parturition are unknown. Clinical studies have quantified cff-DNA levels in the maternal circulation in women who deliver preterm and women who deliver at term and show an association between preterm labor and higher cff-DNA levels in the 2nd, 3rd trimester and at onset of preterm birth symptoms. Together with potential pro-inflammatory properties of cff-DNA, this rise suggests a potential mechanistic role in the pathogenesis of spontaneous preterm birth. In this review, we discuss the evidence linking cff-DNA to adverse pregnancy outcomes, including preterm birth, obtained from preclinical and clinical studies.

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.

Circulating Maternal Total Cell-Free DNA, Cell-Free Fetal DNA and Soluble Endoglin Levels in Preeclampsia: Predictors of Adverse Fetal Outcome? A Cohort Study

BACKGROUND

The diagnosis of preeclampsia (PE) is based on the measurement of maternal blood pressure and proteinuria; however, these parameters are not used in the prediction of adverse fetal outcomes that may occur due to fetal stress. The plasma concentrations of total cell-free DNA (cf-DNA), cell-free fetal DNA (cff-DNA) and soluble endoglin (sEng) are higher in women with established PE than in normotensive controls, and the increase is particularly marked in those with severe PE. We aimed to evaluate the levels of cf-DNA, cff-DNA and sEng in pregnant Egyptian women with PE in order to assess the severity of the disease and to detect their potential utility in the future prediction of time of delivery and adverse fetal outcome.

SUBJECTS AND METHODS

The study included 107 pregnant females with established PE during their third trimester (51 with mild PE and 56 with severe PE), together with 93 normotensive pregnant women. Absolute quantitation of the hemoglobin subunit beta (HBB) and testis-specific protein, Y-linked 1 (TSPY1) genes for the measurement of cf-DNA and cff-DNA in maternal blood, respectively, was carried out using real-time polymerase chain reaction (PCR) together with the measurement of serum sEng using ELISA.

RESULTS

An almost twofold increase in cf-DNA and cff-DNA was detected in the severe PE group over the mild group, and both were significantly different from the control group. Significantly higher levels of cf-DNA, cff-DNA and sEng, with variable magnitudes, were detected in the preterm labor and unfavorable fetal outcome groups compared with the term and favorable outcome groups, respectively. The three markers were almost equivalent with regard to the area under the curve for predicting adverse fetal outcome in the severe PE group. The same was also true for cf-DNA and cff-DNA within the mild PE group.

CONCLUSIONS

Incorporation of cf-DNA, cff-DNA and sEng into the prenatal care service should be considered as a serious addition for the screening and detection of adverse pregnancy outcomes in view of their significant elevations in cases of preeclamptic women whose babies ultimately suffered a poor outcome.

Cell-free DNA fetal fraction and preterm birth

BACKGROUND

Cell-free deoxyribonucleic acid (DNA) is increasingly being used to screen for fetal aneuploidy. The majority of fetal cell-free DNA in the maternal blood results from release from the syncytiotrophoblast as a result of cellular apoptosis and necrosis. Elevated levels of fetal cell-free DNA may be indicative of underlying placental dysfunction, which has been associated with preterm birth. Preliminary studies have demonstrated that fetal cell-free DNA is increased in pregnancies complicated by spontaneous preterm birth. There are limited data on the association between fetal cell-free DNA levels and fetal fraction and preterm birth in asymptomatic women in the first and second trimesters. Preliminary studies have failed to find an association between first-trimester cell-free DNA levels and preterm birth, whereas there is conflicting evidence as to whether elevated second-trimester cell-free DNA is associated with a subsequent spontaneous preterm birth clinical event.

OBJECTIVE

The objective of the study was to evaluate the association between first- and second-trimester cell-free DNA fetal fraction and preterm birth.

STUDY DESIGN

This was a retrospective cohort study of women with singleton pregnancies at increased risk for aneuploidy who had cell-free DNA testing at 10-20 weeks' gestation between October 2011 and May 2014. The cohort was subdivided by gestational age at the time of cell-free DNA testing (10-14 weeks or 14.1-20 weeks). The primary outcome was preterm birth less than 37 weeks' gestation, and the secondary outcomes were preterm birth at less than 34 weeks' gestation and spontaneous preterm birth at less than 37 and 34 weeks' gestation.

RESULTS

Among 1349 pregnancies meeting inclusion criteria 119 (8.8 %) had a preterm birth prior to 37 weeks with 49 cases (3.6 %) delivering prior to 34 weeks. Whereas there was no significant association between fetal fraction and the preterm birth outcomes for those who underwent cell-free DNA testing at 10-14 weeks' gestation, there were significant associations among those screened at 14.1-20.0 weeks' gestation. Fetal fraction greater than or equal to the 95th percentile at 14.1-20.0 weeks' gestation was associated with an increased risk for preterm birth less than 37 and 34 weeks' gestation (adjusted odds ratio, 4.59; 95% confidence interval, 1.39-15.2; adjusted odds ratio, 22.0; 95% confidence interval, 5.02-96.9).

CONCLUSION

Elevated fetal fraction levels at 14.1-20.0 weeks' gestation were significantly associated with an increased incidence of preterm birth. Our findings warrant future exploration including validation in a larger, general population and investigation of the potential mechanisms that may be responsible for the initiation of preterm labor associated with increased fetal cell-free DNA.

Screening for trisomies by cell-free DNA testing of maternal blood: consequences of a failed result

OBJECTIVES

First, to report the distribution of the fetal fraction of cell-free (cf) DNA and the rate of a failed cfDNA test result in trisomies 21, 18 and 13, by comparison with pregnancies unaffected by these trisomies, second, to examine the possible effects of maternal and fetal characteristics on the fetal fraction, and third, to consider the options for further management of pregnancies with a failed result.

METHODS

This was a cohort study of 10 698 singleton pregnancies undergoing screening for fetal trisomies 21, 18 and 13 by cfDNA testing at 10-14 weeks' gestation. There were 160 cases of trisomy 21, 50 of trisomy 18, 16 of trisomy 13 and 10 472 were unaffected by these trisomies. Multivariate regression analysis was used to determine significant predictors of fetal fraction and a failed cfDNA test result amongst maternal and fetal characteristics.

RESULTS

Fetal fraction decreased with increasing body mass index and maternal age, was lower in women of South Asian racial origin than in Caucasians and in assisted compared to natural conceptions. It increased with fetal crown-rump length and higher levels of serum pregnancy-associated plasma protein-A and free β-human chorionic gonadotropin. The median fetal fraction was 11.0% (interquartile range (IQR), 8.3-14.4%) in the unaffected group, 10.7% (IQR, 7.8-14.3%) in trisomy 21, 8.6% (IQR, 5.0-10.2%) in trisomy 18 and 7.0% (IQR, 6.0-9.4%) in trisomy 13. There was a failed result from cfDNA testing after first sampling in 2.9% of the unaffected group, 1.9% of trisomy 21, 8.0% of trisomy 18 and 6.3% of trisomy 13. In the cases with a failed result, 7% of women had invasive testing, mainly because of high risk from the combined test and/or presence of sonographic features suggestive of trisomies 18 and 13. All cases of trisomies were detected prenatally.

CONCLUSIONS

In cases of a failed cfDNA test, the rate of trisomies 18 and 13, but not trisomy 21, is higher than in those with a successful test. In the management of such cases, the decision in favor of invasive testing should depend on the risk of prior screening and the results of detailed ultrasound examination. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Detection of circulating trophoblast particles in maternal blood using density gradient centrifugation in preeclampsia and in normotensive pregnancies

OBJECTIVE

Preeclampsia (PE) is a frequent pregnancy-related disease and a major cause of maternal and fetal morbidity and mortality. Despite that, exact mechanisms of its pathophysiology remain largely unknown. In pregnancies complicated by PE, changes in the regulation of apoptosis seem to result in increased apoptotic shedding of trophoblast particles (TPs) into maternal circulation. Since the number of TP in peripheral blood is low, their detection necessitates pre-analytical enrichment.

METHODS

In this prospective multicenter pilot study we aimed to analyze TP in peripheral blood of 29 women with PE and of 13 unaffected controls using the OncoQuick®plus system for cell enrichment. Using immunocytochemistry, slides were evaluated microscopically for TP. Statistical analyses were performed using Welch's t-test or Fisher's exact test.

RESULTS

TP were detected in 10 (34.5%) women with PE and in two (15.4%) of unaffected controls. More than one TP were only found in PE. Comparing the mean counts of TP between groups, we detected significantly more TP in PE (p = 0.046).

CONCLUSIONS

The OncoQuick®plus system can be applied to detect TP in both women with PE and in normotensive pregnancies. Longitudinal studies investigating the role of TP as a screening method for patients at risk for PE are warranted.

Validation of two-channel sequencing-by-synthesis for noninvasive prenatal testing of fetal whole and partial chromosome aberrations

OBJECTIVE

To validate Illumina's two-channel NextSeq 500 sequencing system for noninvasive prenatal testing (NIPT) of fetal whole chromosome and partial aberrations.

METHODS

A total of 162 plasma samples, previously sequenced for NIPT on a SOLiD 5500xl platform, were sequenced on the NextSeq 500 using 75-bp single-end sequencing, followed by analysis using the WISECONDOR algorithm.

RESULTS

For whole chromosome aneuploidy detection, all samples were classified correctly (in total 3× T13, 3× T18, 8× T21 and 145× euploid). Three partial aberrations (36-Mb terminal loss of 5p, 14-Mb gain on 18p and 33-Mb terminal loss of 13q) were also correctly identified. Fetal fractions in 34 male samples sequenced on both the SOLiD 5500xl and NextSeq 500 platform showed no significant difference. To test robustness, two sample sets, containing both euploid and aneuploid samples, were sequenced on different NextSeq 500 machines, revealing identical results. With unchanged laboratory flow, the NIPT turnaround time could be reduced from 15-16 calendar days to 7-8 calendar days, after switching from the SOLiD 5500xl to the NextSeq 500 platform.

CONCLUSIONS

The NextSeq 500 platform can be used for NIPT to detect both whole and partial chromosome aberrations. It has fast turnaround times and is suitable for mid-sized laboratories.