Procedure-related risk of miscarriage following amniocentesis and chorionic villus sampling: a systematic review and meta-analysis

Statistical Approach to Decreasing the Error Rate of Noninvasive Prenatal Aneuploid Detection caused by Maternal Copy Number Variation

Analyses of cell-free fetal DNA (cff-DNA) from maternal plasma using massively parallel sequencing enable the noninvasive detection of feto-placental chromosome aneuploidy; this technique has been widely used in clinics worldwide. Noninvasive prenatal tests (NIPT) based on cff-DNA have achieved very high accuracy; however, they suffer from maternal copy-number variations (CNV) that may cause false positives and false negatives. In this study, we developed an algorithm to exclude the effect of maternal CNV and refined the Z-score that is used to determine fetal aneuploidy. The simulation results showed that the algorithm is robust against variations of fetal concentration and maternal CNV size. We also introduced a method based on the discrepancy between feto-placental concentrations to help reduce the false-positive ratio. A total of 6615 pregnant women were enrolled in a prospective study to validate the accuracy of our method. All 106 fetuses with T21, 20 with T18, and three with T13 were tested using our method, with sensitivity of 100% and specificity of 99.97%. In the results, two cases with maternal duplications in chromosome 21, which were falsely predicted as T21 by the previous NIPT method, were correctly classified as normal by our algorithm, which demonstrated the effectiveness of our approach.

Reproductive management through integration of PGD and MPS-based noninvasive prenatal screening/diagnosis for a family with GJB2-associated hearing impairment

A couple with a proband child of GJB2 (encoding the gap junction protein connexin 26)-associated hearing impairment and a previous pregnancy miscarriage sought for a reproductive solution to bear a healthy child. Our study aimed to develop a customized preconception-to-neonate care trajectory to fulfill this clinical demand by integrating preimplantation genetic diagnosis (PGD), noninvasive prenatal testing (NIPT), and noninvasive prenatal diagnosis (NIPD) into the strategy. Auditory and genetic diagnosis of the proband child was carried out to identify the disease causative mutations. The couple then received in-vitro-fertilization treatment, and eight embryos were obtained for day 5 biopsy. PGD was performed by short-tandem-repeat linkage analysis and Sanger sequencing of GJB2 gene. Transfer of a GJB2c.235delC heterozygous embryo resulted in a singleton pregnancy. At the 13th week of gestation, genomic DNA (gDNA) from the trio family and cell-free DNA (cfDNA) from maternal plasma were obtained for assessment of fetal chromosomal aneuploidy and GJB2 mutations. NIPT and NIPD showed the absence of chromosomal aneuploidy and GJB2-associated disease in the fetus, which was later confirmed by invasive procedures and postnatal genetic/auditory diagnosis. This strategy successfully prevented the transmission of hearing impairment in the newborn, thus providing a valuable experience in reproductive management of similar cases and potentially other monogenic disorders.

How to perform transabdominal chorionic villus sampling: a practical guideline

The spread of both first trimester screening for chromosomal abnormalities and the possibility to check for single gene disorders at DNA-analysis has increased the request for chorionic villus sampling (CVS) in the first trimester. In order to perform placental biopsy, two routes are possible: the transcervical (TC) and the transabdominal (TA). In early days, the trancervical technique was the most diffused, but since its introduction into clinical practice, the TA technique has become the approach of choice in detriment of the TC technique. In our institution, we have a 30-year experience in TA-CVS with more than 26 000 procedures performed. Considering the expertise and the volume of procedures undertaken at our unit, we suggest a practical guideline for novel operators in TA-CVS.

Emerging issues in invasive prenatal diagnosis: Safety and competency in the post-NIPT era

BACKGROUND

Numbers of invasive prenatal procedures are declining in response to improved aneuploidy screening methods.

OBJECTIVE

To assess current practice and attitudes of clinicians performing invasive prenatal diagnosis in regard to patient consent and safety, maintaining procedural competence and uptake of chromosomal microarrays (CMAs).

METHODS

Anonymous online survey of the Australian Association of Obstetrical and Gynaecological Ultrasonologists conducted in March 2015.

RESULTS

The survey had a 45% response rate with 59 respondents from Australia. Of these, 34 were subspecialists in maternal fetal medicine or obstetric and gynaecological ultrasound. Fifty-six (95%) currently performed amniocentesis or chorionic villus sampling. Of these, 14 (25%) performed <25 procedures and 8 (14%) performed >150 annually, with most respondents (60%) proposing 10-25 amniocenteses/year as adequate activity to maintain their skills. The majority neither expected referrers to provide results of hepatitis B and HIV serology, nor followed up missing results. There was uncertainty regarding the procedure-related vertical transmission risk of HBV in women with high viral load, with most respondents stating they were either unsure of the risk (22%) or that the risk was unknown (30%). Fifty per cent of practitioners routinely ordered CMA after invasive testing; all recommended CMA following a diagnosis of structural abnormality.

CONCLUSIONS

In a period of declining testing, many Australian specialists are performing <25 procedures annually. Consideration of the potential risks of bloodborne viruses is limited. CMAs are rapidly being incorporated into clinical practice. These data have implications for patient consent and safety, and workforce training and practice.

Advantages and Disadvantages of Different Implementation Strategies of Non-Invasive Prenatal Testing in Down Syndrome Screening Programmes

BACKGROUND

Implementation of non-invasive prenatal testing (NIPT) in Down syndrome screening programmes requires health policy decisions about its combination with other tests and its timing in pregnancy.

AIM

Our aim was to aid health policy decision makers by conducting a quantitative analysis of different NIPT implementation strategies.

METHODS

Decision trees were created to illustrate all plausible alternatives in a theoretical cohort of 100,000 pregnant women in five screening programmes: classical screening by the first-trimester combined test (FCT), pre-selection of high-risk women prior to NIPT by the FCT, NIPT as the first screening test at 10 weeks and at 13 weeks, and the simultaneous conductance of NIPT and the FCT.

RESULTS

Pre-selection by FCT prior to NIPT reduces the number of amniocenteses to a minimum because of a reduction of false-positive NIPT results. If NIPT is the first screening test, it detects almost all fetal Down syndrome cases. NIPT at 10 weeks reassures women early in pregnancy, while NIPT at 13 weeks prevents unnecessary tests due to spontaneous miscarriages and allows for immediate confirmation by amniocentesis.

CONCLUSION

Every implementation strategy has its advantages and disadvantages. The most favourable implementation strategy may be NIPT as the first screening test at 13 weeks, offering the most accurate screening test for Down syndrome, when the risk for spontaneous miscarriage has declined remarkably and timely confirmation by amniocentesis can be performed.

Age Does Matter: A Pilot Comparison of Placenta-Derived Stromal Cells for in utero Repair of Myelomeningocele Using a Lamb Model

INTRODUCTION

Fetal amniotic membranes (FM) have been shown to preserve spinal cord histology in the fetal sheep model of myelomeningocele (MMC). This study compares the effectiveness of placenta-derived mesenchymal stromal cells (PMSCs) from early-gestation versus term-gestation placenta to augment FM repair to improve distal motor function in a sheep model.

METHODS

Fetal lambs (n = 4) underwent surgical MMC creation followed by repair with FM patch with term-gestation PMSCs (n = 1), FM with early-gestation PMSCs (n = 1), FM only (n = 1), and skin closure only (n = 1). Histopathology and motor assessment was performed.

RESULTS

Histopathologic analysis demonstrated increased preservation of spinal cord architecture and large neurons in the lamb repaired with early-gestation cells compared to all others. Lambs repaired with skin closure only, FM alone, and term-gestation PMSCs exhibited extremely limited distal motor function; the lamb repaired with early-gestation PMSCs was capable of normal ambulation.

DISCUSSION

This pilot study is the first in vivo comparison of different gestational-age placenta-derived stromal cells for repair in the fetal sheep MMC model. The preservation of large neurons and markedly improved motor function in the lamb repaired with early-gestation cells suggest that early-gestation placental stromal cells may exhibit unique properties that augment in utero MMC repair to improve paralysis.

A Cost-Effectiveness Analysis of First Trimester Non-Invasive Prenatal Screening for Fetal Trisomies in the United States

Background

Non-invasive prenatal testing (NIPT) is a relatively new technology for diagnosis of fetal aneuploidies. NIPT is more accurate than conventional maternal serum screening (MSS) but is also more costly. Contingent NIPT may provide a cost-effective alternative to universal NIPT screening. Contingent screening used a two-stage process in which risk is assessed by MSS in the first stage and, based on a risk cutoff, high-risk pregnancies are referred for NIPT. The objective of this study was to (1) determine the optimum MSS risk cutoff for contingent NIPT and (2) compare the cost effectiveness of optimized contingent NIPT to universal NIPT and conventional MSS.

Study Design

Decision-analytic model using micro-simulation and probabilistic sensitivity analysis. We evaluated cost effectiveness from three perspectives: societal, governmental, and payer.

Results

From a societal perspective, universal NIPT dominated both contingent NIPT and MSS. From a government and payer perspective, contingent NIPT dominated MSS. Compared to contingent NIPT, adopting a universal NIPT would cost $203,088 for each additional case detected from a government perspective and $263,922 for each additional case detected from a payer perspective.

Conclusions

From a societal perspective, universal NIPT is a cost-effective alternative to MSS and contingent NIPT. When viewed from narrower perspectives, contingent NIPT is less costly than universal NIPT and provides a cost-effective alternative to MSS.

Utilization of noninvasive prenatal testing: impact on referrals for diagnostic testing

OBJECTIVE

Since the introduction of noninvasive prenatal testing (NIPT), a marked decrease in prenatal diagnostic testing (chorionic villus sampling [CVS] and amniocentesis) has been observed with unknown potential effects on genetic diagnosis of these pregnancies. The purpose of this study was to understand the impact of NIPT on genetics counseling referrals, diagnostic testing with CVS/amniocentesis, and appropriate use of NIPT.

STUDY DESIGN

A retrospective cohort study was performed on all women referred for genetic counseling and prenatal testing during the 2 years preceding the introduction of NIPT (pre-NIPT) and 2 years following (post-NIPT). The primary outcome was the difference in the number of women referred for genetic counseling and prenatal diagnosis during the pre-NIPT period compared with the post-NIPT period. The secondary outcome was the difference in the number of women referred who were not considered candidates for NIPT between the 2 study periods.

RESULTS

There was a statistically significant reduction in the number of referrals for genetic counseling and diagnostic testing in the post-NIPT compared with the pre-NIPT period (2824 vs 3944, P = .001), a reduction of 28.4%. During the post-NIPT period there was a significant reduction in referrals of women who would not be candidates for NIPT (467 pre-NIPT vs 285 post-NIPT, P = .043). In women who had diagnostic testing with CVS during the study period, 32.4% of the aneuploidies identified would not have been detected by NIPT.

CONCLUSION

There was a significant reduction in the number of patients referred for genetic counseling and prenatal diagnosis following the introduction of NIPT. In addition, there was a significant reduction in the number of patients referred for counseling and testing who would not be candidates for NIPT. This suggests that an increasing number of potential patients are being offered NIPT screening instead of diagnostic testing, including those at risk for fetal single gene disorders and aneuploidies not detectable by NIPT, potentially leading to misdiagnosis.

Transcervical chorionic villus sampling: a practical guide

First trimester screening for fetal aneuploidies has made the implementation of diagnostic techniques essential. Chorionic villus sampling (CVS) is the method of choice for obtaining chorionic villi for molecular and cytogenetic analysis in the first trimester. Two techniques have been developed, a transcervical and a transabdominal. The selection criteria have been based historically on factors, such as placental location, parity, maternal weight and preference of the operator. In our institution, we developed an elevated level of expertise in the field of transcervical approach, resulting in good quality of samples and comparable fetal loss rate to other approaches. Despite three decades of transcervical CVS performance, little consensus in terms of its technique and clinical guidelines exists. Considering the expertise and the volume of procedures performed at our center, we suggest a practical clinical guideline for transcervical CVS.

Copy number variants, aneuploidies, and human disease

In the perinatal setting, chromosome imbalances cause a range of clinically significant disorders and increase the risk for other particular phenotypes. As technologies have improved to detect increasingly smaller deletions and duplications, collectively referred to as copy number variants (CNVs), clinicians are learning the significant role that these types of genomic variants play in human disease and their high frequency in ∼ 1% of all pregnancies. This article highlights key aspects of CNV detection and interpretation used during the course of clinical care in the prenatal and neonatal periods. Early diagnosis and accurate interpretation are important for targeted clinical management.

Cell-free DNA versus intact fetal cells for prenatal genetic diagnostics: what does the future hold?

Prenatal screening and diagnosis is currently focused on the development of a noninvasive prenatal diagnostic test capable of detecting abnormalities similar to those attainable with an invasive test. One contender is cell-free fetal DNA circulating in maternal plasma and the other is intact fetal cells either from the maternal blood or the cervix. Once adequate fetal DNA is available, laboratory analytic techniques, such as sequencing and microarray, can be applied allowing detection of most cytogenetic and Mendelian fetal disorders. The question is: how close are we to achieving this feat, and what does the future hold?

Prenatal genetic care: debates and considerations of the past, present and future

After karyotyping invasively obtained fetal material for decades, the field of prenatal genetic care has changed tremendously since the turn of the century. The introduction of novel technologies and strategies went along with concerns and debates, in which key issues were costs, the finding of variants of unknown or uncertain clinical relevance, commercialization and ethical and social issues. At present, there is an explosion of new genomic technologies, which need critical assessment prior to implementation, especially in the prenatal field. The key issues of the debates we had in the past will again play a major role in guiding us toward careful implementation of these new techniques in future.

Estimation of Detection Rates of Aneuploidy in High-Risk Pregnancy Using an Approach Based on Nuchal Translucency and Non-Invasive Prenatal Testing: A Cohort Study

OBJECTIVES

The aim was to investigate aneuploidy detection using an approach based on nuchal translucency (NT) and non-invasive prenatal testing (NIPT).

METHODS

This was a cohort study including 5,306 high-risk pregnancies with NT measurements and chorionic villus samples (CVS) tested for full karyotype.

RESULTS

The fetal karyotype was normal in 4,172 (78.6%) cases and abnormal in 1,134 (21.4%), including 1,009 with a likely clinically significant adverse outcome. Universal CVS with full karyotyping would lead to the diagnosis of all clinically significant abnormalities. A policy of relying solely on NIPT would have led to the diagnosis of 88.9% of clinically significant abnormalities. A strategy whereby NIPT is the main method, with CVS reserved for cases with NT ≥3.0 mm, would require CVS in 21.7% of cases, identify 94.8% of significant abnormalities and avoid miscarriage in 41 pregnancies compared to CVS for all.

CONCLUSIONS

A policy of NIPT for increased-risk cases and CVS with full karyotype if the NT was ≥3.0 mm reduced the risk of miscarriage yet still identified 95% of clinically significant aneuploidy.

Comparing outcomes and costs between contingent and combined first-trimester screening strategies for Down's syndrome

OBJECTIVE

To compare a contingent strategy with a combined strategy for prenatal detection of Down's syndrome (DS) in terms of cost, outcomes and safety.

STUDY DESIGN

The contingent strategy was based on a simulation, removing measurement of the free beta subunit of human chorionic gonadotropin (free βhCG) and calculating the DS risk retrospectively in 32,371 pregnant women who had been screened with the combined strategy in the first trimester. In the contingent strategy, a risk between 1:31 and 1:1000 in the first trimester indicated further testing in the second trimester (alpha-fetoprotein, inhibin A, unconjugated oestriol and free βhCG). The cut-off risk values for the contingent and combined strategies in the first trimester were 1:30 and 1:250, respectively, and the cut-off risk value for integrated screening in the second trimester was 1:250. Costs were compared in terms of avoided DS births, and the ratio of loss of healthy fetuses following invasive procedures per avoided DS birth was calculated.

RESULTS

The combined strategy had sensitivity of 40/44 (90.9%) and a false-positive rate of 2.8%. Corresponding values for the contingent strategy were 39/44 (88.6%) and 1.3%, respectively. Only 11% of pregnant women required tests in the second trimester, and the approximate cost reduction for each avoided DS birth was 5000€. The ratio of lost healthy fetuses following invasive procedures per avoided DS birth improved by up to 0.65.

CONCLUSION

The contingent strategy has similar effectiveness to the combined strategy, but has lower costs and fewer invasive procedures.

Cell-free DNA screening for fetal aneuploidy as a clinical service

Non-invasive prenatal testing (NIPT) through the analysis of cell free (cf)DNA is revolutionizing prenatal screening for fetal aneuploidy. Current methods used in clinical practice include shotgun massively parallel sequencing (s-MPS); targeted (t-MPS); and an approach that takes advantage of single nucleotide polymorphism (SNP) differences between mother and fetus. Efficacy of cfDNA testing for the common autosomal trisomies far exceeds that of conventional screening. Depending on the methodology used, reasons for discordancy between cfDNA results and fetal karyotype can include true fetal mosaicism, confined placental mosaicism, presence of a maternal karyotype abnormality, insufficient counting due to low fetal fraction, and a vanishing twin. Among the possible cfDNA strategies a Primary test has the highest performance but is expensive, while a Contingent cfDNA test can achieve high performance at a relatively low cost. Practicalities to be considered in the provision of testing include pretest counseling about the scope and accuracy of the testing, the interpretation of results when there is a low fetal fraction and follow-up studies for positive test results. The role of first trimester nuchal translucency measurement and conventional biochemical testing needs to be reassessed in the context of the use of cfDNA.

First trimester contingent testing with either nuchal translucency or cell-free DNA. Cost efficiency and the role of ultrasound dating

OBJECTIVE

To evaluate the performance and cost efficacy of different first-trimester contingent screening strategies based on an initial analysis of biochemical markers.

DESIGN

Retrospective study.

SETTING

Swedish National Quality Register for prenatal diagnosis.

POPULATION

35,780 women with singleton pregnancies.

METHODS

Serum values from first trimester biochemistry were re-analyzed in a contingent approach. For risks between 1:40 and 1:1000, risk estimates from nuchal translucency measurements were added and outcomes were compared using either a final cut-off risk of 1:200 to proceed with invasive testing or offering non-invasive prenatal testing. In a subgroup of 12,836 women with regular menstrual cycles the same analyses were performed using data on the last menstrual period for determining gestational age. The costs of detecting one case of aneuploidy were compared.

MAIN OUTCOME MEASURES

Comparison of screening strategies.

RESULTS

The detection rate was the same (87%) in the contingent group as in complete combined screening, with only 41% requiring a nuchal translucency scan. As an alternative, offering non-invasive prenatal testing to the intermediate risk group would result in a detection rate of 98%, but the cost to detect one case of trisomy 21 would be 83% higher than the cost associated with traditional combined screening.

CONCLUSIONS

First trimester examination using a contingent approach will achieve similar results compared with full combined screening. Non-invasive prenatal testing will not be cost-effective when a high proportion of pregnancies need further testing.

Diagnosis of congenital syphilis and toxoplasmosis

Syphilis, toxoplasmosis, and cytomegalovirus represent disparate entities. The bacterial spirochaete Treponema pallidum ssp. pallidum causes syphilis, the ‘The Great Imitator'; the organism's sole natural host is humans and it remains exquisitely sensitive to penicillin. By contrast, the zoonotic parasite Toxoplasma gondii causes toxoplasmosis. Infection is usually self-limited, although serious disease can occur in the immunocompromised. Meanwhile, the human cytomegalovirus (CMV; human herpesvirus 5) is a relatively prevalent enveloped DNA betaherpesvirus with infection specific to humans. Despite nomenclatural, ecological and therapeutic disparities, however, these agents exhibit several concordances, including various, and at times, cryptic syndromes in child and often mother; congenital infections with potentially devastating outcomes; diagnostic dilemmas. This article primarily discusses the latter of these issues in relationship to congenital syphilis and toxoplasmosis in the Australian context.