Examining the predictive value of fetal fraction on hypertensive disorders of pregnancy.

BACKGROUND: Cell-free fetal DNA (cffDNA) screening is routinely performed in pregnancy. Abnormal fetal fraction has been associated with adverse pregnancy outcomes, including hypertensive disorders of pregnancy, which are associated with severe maternal and neonatal morbidity and mortality. OBJECTIVE: This study examined whether abnormal fetal fraction, defined in this study as fetal fraction either <6 or >15 on the basis of restricted-cubic-spline-plot within our study population, was associated with HDP in a retrospective sample, as well as whether fetal fraction improves the prediction of hypertensive disorders of pregnancy (HDP). We hypothesized that abnormal fetal fraction would be associated with HDP and that adding fetal fraction to a model would significantly improve its strength to predict HDP. STUDY DESIGN: This was a retrospective cohort study of 729 patients delivering singleton, non-anomalous pregnancies with conclusive cffDNA screening. The primary outcome was HDP. Logistic regression models tested associations between fetal fraction and HDP. We evaluated the impact of including fetal fraction on the prediction of hypertensive disorders of pregnancy (HDP) by comparing the area under the receiver operating characteristic (ROC) curve (AUC) between predictive models with and without fetal fraction. RESULTS: Among the study sample, there was an HDP rate of 11.5 %. Abnormal fetal fraction was defined as <6 % percentile and >15 %, HDP incidence was significantly higher in patients with fetal fraction <6 % compared to patients with fetal fraction in normal range (fetal fraction 6-15 %) (19.5 % vs 10.7 %, p = 0.006 on post hoc comparison). Model 1 had one predictor (fetal fraction) with an AUC of 0.59, Model 2 had three predictors (BMI, nulliparity, history of HDP) with an AUC of 0.71, and Model 3 had four predictors (BMI, nulliparity, history of HDP, and fetal fraction) with an AUC of 0.73. Models 2 and 3 were not significantly different (p = 0.18). CONCLUSIONS: More patients who developed HDP had low fetal fraction and fewer patients who developed HDP had high fetal fraction compared to those patients who did not develop HDP. Based on results from multivariable regression models, we cannot conclude that fetal fraction improves HDP prediction. However, developing standardized values for abnormal fetal fraction may be clinically useful.

Performance of Massive Parallel Sequencing-Based Cell-Free DNA Testing in Compromised Pregnancies.

Background/Objectives: Non-Invasive prenatal test (NIPT) is used as a universal or contingent test after prior risk assessment. Screening is mainly performed for common trisomies (T21, T13, T18), although other chromosomal anomalies may be detected. Our objective was to study the performance of GWNIPT in the detection of chromosomal abnormalities in pregnancies in which an invasive prenatal study was performed and in early pregnancy losses, in comparison with the reference test. Method: VeriSeqTM NIPT Solution v2, a genome-wide NIPT (GWNIPT), was performed prior to invasive testing in fetal diagnostic study cases (FDS, n = 155) and in early pregnancy losses (EPL, n = 68). Results: In the FDS group, the diagnostic test (QFPCR, array and karyotype) detected anomalies in 32 pregnancies (21%), in twenty of them (61%) also detected by GWNIPT. Eleven of the twelve cases undetected by GWNIPT were balanced translocations (n = 4) or deletions/duplications <7 Mb (n = 7). In the EPL group, GWNIPT detected anomalies in 46% of cases (31/68) but comparison with reference test (QFPCR and karyotype) in products of conception (POC) was only possible in 18 cases. Concordant results between POC and GWNIPT test were obtained in 16 of the 18 cases. In EPL, with GWNIPT testing, common trisomies accounted for 25.8% of cases (8/31), rare trisomies 54.8% (17/31) and microdeletions/duplications 16.1% (5/31). Conclusions: The GWNIPT test may be useful in clinical practice in prenatal and in EPL's genetic diagnosis when the appropriate sample is not available.

Advancements of non-invasive prenatal testing: the role of obstetricians.

Since its debut in 2011, Non-Invasive Prenatal Testing (NIPT) has continually demonstrated its effectiveness in detecting an expanding number of diseases. NIPT offers a less invasive approach to prenatal chromosomal disease screening, providing prospective parents with vital information to better prepare for their potential pregnancy outcomes. NIPT was primarily designed for screening trisomy 13, 18, and 21. However, its scope has since broadened to encompass microdeletions and autosomal dominant monogenic diseases. Conversely, the normalization of NIPT can have unintended consequences. Some patients opt for NIPT without any medical indications, driven by a desire to remain cautious. This over-screening for chromosomal abnormalities can exacerbate pregnancy-related anxiety, as individuals might feel pressured into taking the test unnecessarily. While NIPT can be highly successful when conducted correctly, it is not infallible, and obstetricians play a crucial role in managing patient expectations. This includes providing genetic counseling to individuals with relevant genetic information regarding their personal and family histories. In the context of NIPT, a bioinformatics analysis is performed on a cell-free DNA (cfDNA) sample extracted from the mother's placenta to determine the fetal fraction (FF). This FF measurement is vital for quality control and ensuring statistical confidence in the test results. Raising awareness among clinicians about the significance of FF enhances patient care and alleviate concerns about the possibility of failed NIPT. This paper aims to explore the ongoing debates and more specifically the significance and pitfalls of NIPT on a psychosocial and ethical scale, all while highlighting the importance of genetic counseling.

The performance evaluation of NIPT for fetal chromosome microdeletion/microduplication detection: a retrospective analysis of 68,588 Chinese cases.

Background: Chromosomal abnormalities are the main cause of birth defects in newborns. Since the inception of noninvasive prenatal testing (NIPT) technology, it has primarily been applied to the detection of common trisomy (T21, T18, T13). However, the application of NIPT in microdeletion and microduplication detection is still controversial. Methods: This study retrospectively analyzed the data of 68,588 cases that underwent NIPT at Ganzhou Maternal and Child Health Hospital in China. These data were used to evaluate the performance of NIPT in fetal chromosome microdeletion/microduplication detection and to investigate the key factors affecting the NIPT performance. Results: A total of 281 cases (0.41%) had positive NIPT results with copy number variants (CNVs), of which 161 were validated by karyotyping and chromosome microarray analysis (CMA). Among the 161 cases, 92 were confirmed as true positives through karyotyping or CMA, including 61 microdeletion cases and 31 microduplication cases, resulting in a positive predictive value (PPV) of 57.14%. Improvements in library construction methods increased the fraction of cell-free fetal DNA (cffDNA) from 13.76% to 18.44%, leading to a significant improvement in the detection rate (0.47% vs. 0.15%) and PPV (59.86% vs. 28.57%) of NIPT for CNVs. Conclusion: This study proved the robust performance of NIPT for fetal chromosome microdeletion/microduplication detection. In addition, the cffDNA fraction is a key factor influencing NIPT, with increased cffDNA fraction improving the performance of NIPT.

Stretch Causes cffDNA and HMGB1-Mediated Inflammation and Cellular Stress in Human Fetal Membranes.

Danger-associated molecular patterns (DAMPs) are elevated within the amniotic cavity, and their increases correlate with advancing gestational age, chorioamnionitis, and labor. Although the specific triggers for their release in utero remain unclear, it is thought that they may contribute to the initiation of parturition by influencing cellular stress mechanisms that make the fetal membranes (FMs) more susceptible to rupture. DAMPs induce inflammation in many different tissue types. Indeed, they precipitate the subsequent release of several proinflammatory cytokines that are known to be key for the weakening of FMs. Previously, we have shown that in vitro stretch of human amnion epithelial cells (hAECs) induces a cellular stress response that increases high-mobility group box-1 (HMGB1) secretion. We have also shown that cell-free fetal DNA (cffDNA) induces a cytokine response in FM explants that is fetal sex-specific. Therefore, the aim of this work was to further investigate the link between stretch and the DAMPs HMGB1 and cffDNA in the FM. These data show that stretch increases the level of cffDNA released from hAECs. It also confirms the importance of the sex of the fetus by demonstrating that female cffDNA induced more cellular stress than male fetuses. Our data treating hAECs and human amnion mesenchymal cells with HMGB1 show that it has a differential effect on the ability of the cells of the amnion to upregulate the proinflammatory cytokines and propagate a proinflammatory signal through the FM that may weaken it. Finally, our data show that sulforaphane (SFN), a potent activator of Nrf2, is able to mitigate the proinflammatory effects of stretch by decreasing the levels of HMGB1 release and ROS generation after stretch and modulating the increase of key cytokines after cell stress. HMGB1 and cffDNA are two of the few DAMPs that are known to induce cytokine release and matrix metalloproteinase (MMP) activation in the FMs; thus, these data support the general thesis that they can function as potential central players in the normal mechanisms of FM weakening during the normal distension of this tissue at the end of a normal pregnancy.

Antenatal RHD screening to guide antenatal anti-D immunoprophylaxis in non-immunized D- pregnant women.

In pregnancy, D- pregnant women may be at risk of becoming immunized against D when carrying a D+ fetus, which may eventually lead to hemolytic disease of the fetus and newborn. Administrating antenatal and postnatal anti-D immunoglobulin prophylaxis decreases the risk of immunization substantially. Noninvasive fetal RHD genotyping, based on testing cell-free DNA extracted from maternal plasma, offers a reliable tool to predict the fetal RhD phenotype during pregnancy. Used as a screening program, antenatal RHD screening can guide the administration of antenatal prophylaxis in non-immunized D- pregnant women so that unnecessary prophylaxis is avoided in those women who carry a D- fetus. In Europe, antenatal RHD screening programs have been running since 2009, demonstrating high test accuracies and program feasibility. In this review, an overview is provided of current state-of-the-art antenatal RHD screening, which includes discussions on the rationale for its implementation, methodology, detection strategies, and test performance. The performance of antenatal RHD screening in a routine setting is characterized by high accuracy, with a high diagnostic sensitivity of ≥99.9 percent. The result of using antenatal RHD screening is that 97-99 percent of the women who carry a D- fetus avoid unnecessary prophylaxis. As such, this activity contributes to avoiding unnecessary treatment and saves valuable anti-D immunoglobulin, which has a shortage worldwide. The main challenges for a reliable noninvasive fetal RHD genotyping assay are low cell-free DNA levels, the genetics of the Rh blood group system, and choosing an appropriate detection strategy for an admixed population. In many parts of the world, however, the main challenge is to improve the basic care for D- pregnant women.

Association of fetal fraction and cell-free fetal DNA with adverse pregnancy outcomes: A systematic review.

BACKGROUND: Adverse pregnancy outcomes, which can be caused by multiple factors, present a significant threat to the health of mothers and their babies. Cell-free fetal DNA (cffDNA) from placental trophoblast cells might be able to reflect placental and fetal status. Previous studies have yielded controversial results regarding the association of FF or cffDNA with various adverse pregnancy outcomes. A previous study has attempted to systematically assess the association between low fetal fraction (FF) and adverse pregnancy outcomes, but it failed to perform quantitative analyses due to the few studies included. In the present study, we attempted to quantitatively assess the association of FF (or cffDNA) with adverse pregnancy outcomes and further analyze the causes of heterogeneity. OBJECTIVES: To investigate the association of high/low FF or cffDNA with adverse pregnancy outcomes. SEARCH STRATEGY: We searched the databases of PubMed, Embase, Cochrane, and Web of Science from January 1, 1990, to June 15, 2022 in this meta-analysis. SELECTION CRITERIA: Studies on the relationships of adverse pregnancy outcomes in women with FF or cell free DNA were included. Non-English literature was excluded. DATA COLLECTION AND ANALYSIS: Data about pregnancy outcomes and cell free DNA were extracted and meta-analyzed. Subgroup analysis was performed by different outcomes. MAIN RESULTS: There were 11 studies included involving 8280 participants. No significant heterogeneity was observed among the studies (I2 = 27%, 25%), and a fixed-effect model was used for weighted quantitative analysis. The results revealed that the FF or cffDNA during pregnancy was significantly associated with adverse pregnancy outcomes in pregnant women (OR = 1.57, 95% CI [1.24, 1.99], P = 0.233). The overall incidence of the maternal adverse outcomes was 8% (95% CI: 5-13). Subgroup analysis of different outcomes showed an evident association between low FF or cffDNA and hypertensive disorders of pregnancy (HDP) (OR = 1.76, 95% CI [1.36, 2.27], P = 0.581). There was no evidence that the occurrence of spontaneous preterm birth (sPTB) and placental abnormality was associated with FF or cffDNA. No association was observed between low FF or cffDNA during pregnancy and adverse outcomes in fetuses (OR = 1.39, 95% CI [0.99, 1.94], P = 0.242). The overall incidence of adverse outcomes in fetuses was 8% (95% CI: 6-11). There were controversies over the association between high FF or cffDNA and HDP, and sPTB and small for gestational age infant, among different studies. CONCLUSIONS: Pregnant women with low FF or cffDNA during the first or second trimester of pregnancy have an overall increased risk of adverse pregnancy outcomes, especially HDP. However, the association between FF and various pregnancy outcomes needs to be further explored by more prospective studies.

Noninvasive Prenatal Diagnosis of SEA-Thalassemia by Combining 1000 Genomes Database and Relative Haplotype Dosage.

To explore a noninvasive method for diagnosis of SEA-thalassemia and to investigate whether the regional factors affect the accuracy of this method. The method involved using a public database and bioinformatics software to construct parental haplotypes for proband and predicting fetal genotypes using relative haplotype dosage. We screened and downloaded sequencing data of couples who were both SEA-thalassemia carriers from the China National Genebank public data platform, and matched the sequencing data format with that of the reference panel using Ubuntu system tools. We then used Beagle software to construct parental haplotypes, predicted fetal haplotypes by relative haplotype dosage. Finally, we used Hidden Markov Model and Viterbi algorithm to determine fetal pathogenic haplotypes. All noninvasive fetal genotype diagnosis results were compared with gold standard gap-PCR electrophoresis results. Our method was successful in diagnosing 13 families with SEA-thalassemia carriers. The best diagnostic results were obtained when Southern Chinese Han was used as the reference panel, and 10 families showed full agreement between our noninvasive diagnostic results and the gap-PCR electrophoresis results. The accuracy of our method was higher when using a Chinese Han as the reference panel for haplotype construction in the Southern Chinese Han region as opposed to Beijing Chinese region. The combined use of public databases and relative haplotype dosage for diagnosing SEA-thalassemia is a feasible approach. Our method produces the best noninvasive diagnostic results when the test samples and population reference panel are closely matched in both ethnicity and geography. When constructing parental haplotypes with our method, it is important to consider the effect of region in addition to population background alone.

Cell­free fetal DNA at 11­13 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 ß-human chorionic gonadotropin (ß-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, ß-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.

Performance of noninvasive prenatal screening for fetal sex chromosome aneuploidies in a cohort of 116,862 pregnancies.

BACKGROUND: Noninvasive prenatal screening (NIPS) has shown good performance in screening common aneuploidies. However, its performance in detecting fetal sex chromosome aneuploidies (SCAs) needs to be evaluated in a large cohort. RESEARCH DESIGN AND METHODS: In this retrospective observation, a total of 116,862 women underwent NIPS based on DNA nanoball sequencing from 2015 to 2022. SCAs were diagnosed based on karyotyping or chromosomal microarray analysis (CMA). Among them, 2,084 singleton pregnancies received karyotyping and/or CMA. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of NIPS for fetal SCAs were evaluated. RESULTS: The sensitivity was 97.7% (95%CI, 87.7-99.9), 87.3% (95% CI, 76.5-94.4), 96.1% (95%CI, 86.5-99.5), and 95.7% (95% CI, 78.1-99.9), the PPV was 25.8% (95%CI, 19.2-33.2), 80.9% (95%CI, 69.5-89.4), 79.0% (95%CI, 66.8-88.3), and 53.7% (95%CI, 37.4-69.3) for 45,X, 47,XXY, 47,XXX, and 47,XYY, respectively. The specificity was 94.1% (95%CI, 93.0-95.1) for 45,X, and more than 99.0% for sex chromosome trisomy (SCT). The NPV was over 99.0% for all. CONCLUSIONS: NIPS screening for fetal SCAs has high sensitivity, specificity and NPV. The PPV of SCAs was moderate, but that of 45,X was lower than that of SCTs. Invasive prenatal diagnosis should be recommended for high-risk patients.

First Trimester Contingent Screening for Aneuploidies with Cell-Free Fetal DNA in Singleton Pregnancies - a Swiss Single Centre Experience.

Introduction: Switzerland was amongst the first countries to offer cell-free fetal DNA (cffDNA) testing covered by the health insurance to pregnant women with a risk ≥ 1:1000 for trisomies at first trimester combined screening (FTCS). The aim of this study is to evaluate the implementation of this contingent model in a single tertiary referral centre and its effect on gestational age at diagnosing trisomy 21. Materials and Methods: Between July 2015 and December 2020 all singleton pregnancies at 11-14 weeks of gestation without major fetal malformation were included and stratified according to their risk at FTCS. Statistical analysis was performed by GraphPad Version 9.1 for Windows. Results: 4424 pregnancies were included. Of 166 (3.8%) pregnancies with a NT ≥ 3.5 mm and/or a risk ≥ 1:10 at FCTS, 130 (78.3%) opted for direct invasive testing. 803 (18.2%) pregnancies had an intermediate risk, 692 (86.2%) of them opted for cffDNA first. 3455 (78.1%) pregnancies had a risk < 1:1000. 63 fetuses were diagnosed with trisomy 21, 47 (74.6%) directly by invasive procedures after FTCS, 16 (25.4%) by cffDNA first. Conclusions: Most women choose cffDNA or invasive testing as second tier according to national guidelines. Despite the delay associated with cffDNA testing after FCTS, 75% of all trisomy 21 are still diagnosed in the first trimester with this contingent screening model.

Exploring factors impacting haplotype-based noninvasive prenatal diagnosis for single-gene recessive disorders.

Haplotype-based noninvasive prenatal diagnosis (NIPD) is applicable for various recessive single-gene disorders in proband families. However, a comprehensive exploration of critical factors influencing the assay performance, such as fetal fraction, informative single nucleotide polymorphism (SNP) count, and recombination events, has yet to be performed. It is critical to identify key factors affecting NIPD performance, including its accuracy and success rate, and their impact on clinical diagnostics to guide clinical practice. We conducted a prospective study, recruiting 219 proband families with singleton pregnancies at risk for eight recessive single-gene disorders (Duchenne muscular dystrophy, spinal muscular atrophy, phenylketonuria, methylmalonic acidemia, hemophilia A, hemophilia B, non-syndromic hearing loss, and congenital adrenal hyperplasia) at 7-14 weeks of gestation. Haplotype-based NIPD was performed by evaluating the relative haplotype dosage (RHDO) in maternal circulation, and the results were validated via invasive prenatal diagnosis or newborn follow-ups. Among the 219 families, the median gestational age at first blood draw was 8+5 weeks. Initial testing succeeded for 190 families and failed for 29 due to low fetal fraction (16), insufficient informative SNPs (9), and homologous recombination near pathogenic variation (4). Among low fetal fraction families, successful testing was achieved for 11 cases after a redraw, while 5 remained inconclusive. Test failures linked to insufficient informative SNPs correlated with linkage disequilibrium near the genes, with F8 and MMUT exhibiting the highest associated failure rates (14.3% and 25%, respectively). Homologous recombination was relatively frequent around the DMD and SMN1 genes (8.8% and 4.8%, respectively) but led to detection failure in only 44.4% (4/9) of such cases. All NIPD results from the 201 successful families were consistent with invasive diagnostic findings or newborn follow-up. Fetal fraction, informative SNPs count, and homologous recombination are pivotal to NIPD performance. Redrawing blood effectively improves the success rate for low fetal fraction samples. However, informative SNPs count and homologous recombination rates vary significantly across genes, necessitating careful consideration in clinical practice. We have designed an in silico method based on linkage disequilibrium data to predict the number of informative SNPs. This can identify genomic regions where there might be an insufficient number of SNPs, thereby guiding panel design. With these factors properly accounted for, NIPD is highly accurate and reliable.

Fetal fraction of cell-free DNA in noninvasive prenatal testing and adverse pregnancy outcomes: a nationwide retrospective cohort study of 56,110 pregnant women.

BACKGROUND: Noninvasive prenatal testing by cell-free DNA analysis is offered to pregnant women worldwide to screen for fetal aneuploidies. In noninvasive prenatal testing, the fetal fraction of cell-free DNA in the maternal circulation is measured as a quality control parameter. Given that fetal cell-free DNA originates from the placenta, the fetal fraction might also reflect placental health and maternal pregnancy adaptation. OBJECTIVE: This study aimed to assess the association between the fetal fraction and adverse pregnancy outcomes. STUDY DESIGN: We performed a retrospective cohort study of women with singleton pregnancies opting for noninvasive prenatal testing between June 2018 and June 2019 within the Dutch nationwide implementation study (Trial by Dutch Laboratories for Evaluation of Non-Invasive Prenatal Testing [TRIDENT]-2). Multivariable logistic regression analysis was used to assess associations between fetal fraction and adverse pregnancy outcomes. Fetal fraction was assessed as a continuous variable and as <10th percentile, corresponding to a fetal fraction <2.5%. RESULTS: The cohort comprised 56,110 pregnancies. In the analysis of fetal fraction as a continuous variable, a decrease in fetal fraction was associated with increased risk of hypertensive disorders of pregnancy (adjusted odds ratio, 2.27 [95% confidence interval, 1.89-2.78]), small for gestational age neonates <10th percentile (adjusted odds ratio, 1.37 [1.28-1.45]) and <2.3rd percentile (adjusted odds ratio, 2.63 [1.96-3.57]), and spontaneous preterm birth from 24 to 37 weeks of gestation (adjusted odds ratio, 1.02 [1.01-1.03]). No association was found for fetal congenital anomalies (adjusted odds ratio, 1.02 [1.00-1.04]), stillbirth (adjusted odds ratio, 1.02 [0.96-1.08]), or neonatal death (adjusted odds ratio, 1.02 [0.96-1.08]). Similar associations were found for adverse pregnancy outcomes when fetal fraction was <10th percentile. CONCLUSION: In early pregnancy, a low fetal fraction is associated with increased risk of adverse pregnancy outcomes. These findings can be used to expand the potential of noninvasive prenatal testing in the future, enabling the prediction of pregnancy complications and facilitating tailored pregnancy management through intensified monitoring or preventive measures.

Diagnóstico prenatal no invasivo basado en ADN libre fetal: actualización

El descubrimiento del ADN libre fetal circulando en sangre materna ha revolucionado la práctica de la Obstetricia y cambiado el paradigma del diagnóstico prenatal. En los últimos 5 años hemos avanzado del tamizaje de aneuplodías con muchos falsos positivos a uno mucho más efectivo y con cifras de falsos positivos muy bajas. Este es, sin duda, el mejor método de tamizaje actual que se tiene en Obstetricia.

The discovery of cell free fetal DNA (cff-DNA) in maternal circulation has profoundly changed the clinical practice of Obstetrics and knocked down an old paradigm in prenatal diagnosis. Over the past five years screening for chromosomal abnormalities has moved from one with a high false positive rate into another more effective and at lower false positive rate. Undoubtedly, this test is the best effective screening tool in Obstetrics.

Diagnóstico prenatal no invasivo: Ácidos nucleicos de origen fetal en sangre materna / Non invasive prenatal diagnosis: Fetal nucleic acid analysis in maternal blood

Las técnicas actuales de diagnóstico prenatal de enfermedades génicas y cromosómicas incluyen procedimientos invasivos que conllevan un pequeño, pero significativo, riesgo. Por muchos años se ha estudiado la posibilidad de utilizar células fetales en circulación materna; sin embargo, ha fracasado su implementación clínica debido a su escasez y persistencia luego del parto. Desde hace más de una década se detectó ADN fetal libre en sangre de embarazadas. Este sería de origen placentario e indetectable después del parto, y fuente de material fetal para el desarrollo de técnicas diagnósticas utilizando sangre materna. No obstante, la mayoría del ADN libre en circulación materna es de origen materno con una contribución fetal del 3% al 6% aumentando a lo largo de la gestación. Dado que los métodos actuales no permiten separar el ADN libre fetal del materno, las aplicaciones se focalizan en el análisis de genes no presentes en la madre, tales como secuencias del cromosoma Y, o gen RHD en madres Rh negativas, o mutaciones paternas o de novo. Asimismo, la detección de ARN fetal libre en sangre de embarazadas abrió la posibilidad de obtener información acerca de patrones de expresión génica de tejidos embrionarios y, utilizando genes que se expresan sólo en la unidad feto-placentaria, se podría establecer un control de presencia de material fetal, independiente del material genético de la madre. El presente trabajo describe las evidencias acerca del pasaje de ácidos nucleicos fetales a circulación materna, su aplicación actual en el diagnóstico prenatal y posibles usos futuros.

Current prenatal diagnosis of monogeneic and chromosomal diseases, includes invasive procedures which carry a small but significant risk. For many years, analysis of fetal cells in maternal circulation has been studied, however it has failed its clinical use due to the scarcity of these cells and their persistance after delivery. For more than a decade, the presence of cell-free fetal DNA in maternal blood has been identified. These fetal DNA fragments would derive from the placenta and are not detected after delivery, making them a source of fetal material for carrying out diagnosis techniques using maternal blood. However, the vast majority of cell free DNA in maternal circulation is of maternal origin, with the fetal component contributing from 3% to 6% and rising towards term. Available methodologies do not allow separation of fetal from maternal cell free DNA, so current applications have been focused on the analysis of genes not present in the mother, such as Y chromosome sequences, or RHD gene in RhD-negative women, or paternal or de novo mutations. Also, the detection of cell-free fetal RNA in maternal blood offers the possibility of obtaining information regarding genetic expression profiles of embrionic tissues, and using genes expressed only at the feto-placental unit, controls for the presence of fetal material could be established, regardless of maternal genetic tissue. The present article describes the evidences regarding the passage of fetal nucleic acids to maternal circulation, its current prenatal diagnosis application and possible future perspectives.