Review of Prenatal Aneuploidy Screening Uptake Rate and Trends in Iran, and Developed Countries

: Prenatal screening of different anomalies including chromosomal aneuploidies have become a part of routine pregnancy care in most countries around the world. These tests can help pregnant mothers to have informed decisions. In this study we gathered relevant scientific and governmental/official data about uptake rate of these screenings in different developed countries and Iran. We have tried to use the latest articles and reports, and also consider to the global trend of screening and abortion policies in developed countries. Also, some pitfalls when comparing prenatal screening of different countries will be explained. These data can help to have a better insight about Iran’s prenatal screening status when compared with developed countries to improve public health policies.

The Role of de novo Variants in Patients with Congenital Diaphragmatic Hernia

The genetic etiology of congenital diaphragmatic hernia (CDH), a common and severe birth defect, is still incompletely understood. Chromosomal aneuploidies, copy number variations (CNVs), and variants in a large panel of CDH-associated genes, both de novo and inherited, have been described. Due to impaired reproductive fitness, especially of syndromic CDH patients, and still significant mortality rates, the contribution of de novo variants to the genetic background of CDH is assumed to be high. This assumption is supported by the relatively low recurrence rate among siblings. Advantages in high-throughput genome-wide genotyping and sequencing methods have recently facilitated the detection of de novo variants in CDH. This review gives an overview of the known de novo disease-causing variants in CDH patients.

Expanded Noninvasive Prenatal Testing for Chromosomal aneuploidies and Copy Number Variants in a Cohort of 16128 Single Pregnancies

Background: Noninvasive prenatal testing (NIPT) is based on second-generation genomic sequencing technology to scan cell-free fetal DNA originating from the placenta in maternal plasma. As the depth of sequencing increases, it can be used to focus on chromosomal aneuploidies, copy number variants (CNVs), and monogenic diseases. It can significantly improve the accuracy of prenatal screening and reduces the number of invasive testing.Methods: In this study, we retrospectively analyzed 16128 naturally conceived singleton pregnancies who underwent expanded NIPT to calculate the true positive rate (TPR) of chromosomal aneuploidies and CNVs, and analyzed the potential influence of maternal sex chromosome abnormalities (SCAs) and maternal CNVs on expanded NIPT results.Results: After invasive prenatal diagnosis and follow-up, 103 pregnancies were found to be true-positive, including 73 cases of chromosomal abnormalities and 30 cases of CNVs. The TPR of T21 was 84.62%, T18 was 50.00%, T13 was 22.22%, SCA was 34.06%, and CNVs was 40.28%. In addition, we found that the positive rate of aneuploidies increased with maternal age and that maternal SCAs accounted for 13.33% of the 60 false positive cases of SCAs.Conclusion: Expanded NIPT showed high sensitivity and specificity in detecting diseases of chromosomal abnormalities. It also shows good performance in detecting CNVs, but maternal SCAs and CNVs confused some NIPT results, indicating it is still necessary to study the potential maternal influence on expanded NIPT results and to report related clinical validation studies.

Detection of Aneuploidies in Products of Conception and Neonatal Deaths in Iranian Patients Using the Multiplex Ligation-Dependent Probe Amplification (MLPA)

Background: Around 70% of all pregnancies (Including 15% of clinically-recognized ones) are lost due to various fetal or maternal disorders. Chromosomal aneuploidies are among the most common causes of pregnancy loss. Standard chromosome analysis using G-banding technique (Karyotype) is the technique of choice in studying such abnormalities; however, this technique is time-consuming and sensitive, and limited by vulnerabilities such as cell culture failure. The use of molecular cytogenetic techniques, including array-based techniques and Multiplex Ligation-Dependent Probe Amplification (MLPA), has been proposed to overcome the limitations of this method to study the products of conception. This study has been designed to investigate the feasibility of using MLPA technique as a standalone genetic testing, with histopathologic examinations and genetic counseling to detect aneuploidies in products of conception and neonatal deaths. Methods: Forty-two verified fetal and neonatal samples were studies and genetic counseling was scheduled for all parents. Histopathologic examinations were carried out on the products of conception, and appropriate fetal tissues were separated for genetic studies. Following DNA extraction and purification, MLPA was carried out to investigate chromosomal aneuploidies. Results: Nine samples (21.42%) were diagnosed to be affected with aneuploidy. Detected aneuploidies were trisomy 22 (n=3), trisomy 21(n=1), trisomy 18 (n=2), trisomy 16 (n=1), trisomy 13 (n=1), and monosomy of chromosome X (n=1). The MLPA analysis results were conclusive for all of the fetal samples (Success rate: 100%). Conclusion: These results suggest that MLPA, as a standalone genetic testing, is an accurate, rapid, and reliable method in overcoming the limitations of standard cytogenetic techniques in genetic investigation of products of conception.

Chromosomal aneuploidies and associated rare genetic syndromes involved in male infertility

Background and objectives: Recent investigations have reported more than 70 genetic syndromes involved in male infertility; however, the majority of these syndromes are extremely rare. We aimed to report the most common chromosomal abnormalities and associated rare genetic syndromes in the context of human male infertility. Materials and Methods: We performed a review of published articles considering the most common chromosomal aneuploidies and rare genetic syndromes associated with male infertility on PubMed, Web of Science, and Scopus. Results: Chromosomal abnormalities are frequently found in infertile men, with an incidence rate of 2-15%. The chromosomal aberrations include the sex and autosomal chromosome abnormalities, as well as numerical and structural defects in chromosomes. There are various rare genetic syndromes involved in male infertility that are caused by structural and numerical abnormalities in chromosomes. Klinefelter syndrome is the most common type of sex chromosome aneuploidy in infertile males. Besides, Y chromosome microdeletions, particularly in azoospermia factor regions, serve as the second most common genetic cause of impaired spermatogenetic in infertile men. These molecular genetic abnormalities not only can be inherited, but also they may transmit to the next generation through assisted reproductive techniques and result in the birth of boys with higher risk of congenital abnormalities and infertility. Despite the normal secondary male sexual characteristics, some patients are azoospermic or severe oligozoospermic men. Therefore, identification of these molecular genetic factors and rare genetic disorders is essential in men with unexplained infertility. Discussion and conclusion: Since most of molecular genetic abnormalities can be transmitted to the next generation, identification of these rare genetic disorders is crucial for men with unexplained infertility. It is also essential for clinicians and physicians of reproductive medicine and andrologists to initiate genetic evaluation, aneuploidy screening and counseling prior to any therapeutic procedures.

CORRELATION BETWEEN INCIDENCE OF X-MONOSOMY AND COSMIC BACKGROUND RADIATION

Objective: Examining the incidence of X-monosomy among chromosomal aneuploidies with relation to cosmic background radiation. Method: We have processed the results of prenatal chromosome investigations performed in the 26-year period between 1990 and 2015. In the current study, we have paid special attention to abnormalities affecting the fetal sex chromosomes. The incidence of X-monosomy among sex chromosomal aneuploidies was studied in view of the intensity of cosmic background radiation. Results: In the 26-year period total of 43,272 fetal chromosomal investigations were carried out at our Department. In that period, sex chromosomal abnormality was detected in 230 cases (0.53 %), 92 of which (0.21 %) turned out to be X-monosomies. An uneven incidence ratio of X-monosomy could be observed as producing a wave line. As compared to nearby years, a peak was noted in 1997 (17 cases), somewhat smaller peak involving six cases was observed in 2002, likewise, 2008 yielded another small peak with five cases. Similar curves were obtained when mosaic and non-mosaic forms were studied separately. Based on the above, we looked for a mutagenic effect that could have been present in an explicit form around about the year 1997 and be associated with the higher incidence of X-monosomy in that period. An increase in the intensity of cosmic radiation could be one of those effects. The extremely high rate of chromosomal aberrations in 1997 coincided with the local minimum of the solar flares, therefore solar radiation could not be blamed for those aberrations. At the same time, however is suggestive of a causal relationship between the increase in galactic cosmic background radiation flux and higher incidence of X-monosomy around about 1997. Conclusions: Examining the incidence of sex chromosome aberrations, with special regard to X-monosomy, we have concluded the latter occurred more frequently during higher cosmic background radiation.

International experience in organizing non-invasive prenatal testing

Non-invasive prenatal testinging (NIPT) is a relatively new method aimed at detecting fetal chromosomal aneuploidies by analyzing extracellular fetoplacental DNA in the blood of a pregnant woman. NIPT has high sensitivity and specificity, and many professional communities now recommend its use as a screening method. Since its introduction into clinical practice in Hong Kong in 2011, NIPT has expanded rapidly around the world. The experience of various countries in organizing non-invasive prenatal testing is described in this article. Key words: NIPT, non-invasive prenatal testing, extracellular fetoplacental DNA, prenatal screening, prenatal diagnosis, invasive prenatal diagnosis, aneuploidy

Reanalysis of discarded blastocysts for autosomal aneuploidy after sex selection in cleavage-stage embryos

Objective: The goal of the present study was to investigate the rate of chromosomal aneuploidies in surplus embryos after sex determination at the cleavage stage. Then, the same chromosomal aneuploidies were evaluated in blastocysts after extended culture.Methods: Sixty-eight surplus embryos were biopsied at the cleavage stage and incubated for an additional 3 days to allow them to reach the blastocyst stage. The embryos were reanalyzed via fluorescence in situ hybridization (FISH) to examine eight chromosomes (13, 15, 16, 18, 21, 22, X, and Y) in both cleavage-stage embryos and blastocysts.Results: Although the total abnormality rate was lower in blastocysts (32.35%) than in cleavage-stage embryos (45.58%), the difference was not significant (p=0.113). However, when we restricted the analysis to autosomal abnormalities, we observed a significant difference in the abnormality rate between the cleavage-stage embryos (44.11%) and the blastocysts (17.64%, p=0.008). A higher rate of sex chromosomal abnormalities was also observed in cleavage-stage embryos (29.4%) than in blastocysts (14.70%, p=0.038). Conclusion: The data indicated that embryo biopsy should be conducted at the blastocyst stage rather than the cleavage stage. The results also emphasized that examination of common chromosomal aneuploidies apart from sex selection cycles can be conducted in the blastocyst stage with the FISH method.

Analysis of cell-free DNA in a consecutive series of 13,607 routine cases for the detection of fetal chromosomal aneuploidies in a single center in Germany

Purpose Noninvasive prenatal testing (NIPT) is a highly sensitive and specific method for detection of fetal chromosomal aneuploidies from maternal plasma. The objective of this study was to determine the performance of a new paired-end sequencing-based NIPT assay in 13,607 pregnancies from a single center in Germany. Methods Samples from 13,607 pregnant women who previously underwent NIPT were analyzed using VeriSeq NIPT Solution v2 assay for presence of common fetal trisomies and monosomy X. Follow-up to determine clinical truth was carried out. Results Of the 13,607 cases, 13,509 received a NIPT call resulting in a low study failure rate of 0.72%. There were 188 (1.4%) high-risk calls: 117 trisomy 21, 34 trisomy 18, 23 trisomy 13, one trisomy 21 + 13, and 13 monosomy X. High sensitivities and specificities of ≥ 98.89% were reported for all four aneuploidy conditions. Of the high-risk cases, clinical follow-up data were available for 77.1% (145/188). Clinical follow-up of high-risk calls revealed an overall positive predictive value of 84.8% (potential range 65.4–88.3%). NIPT results were provided for samples across a range of fetal fractions, down to 2% fetal fraction. Conclusion The VeriSeq NIPT Solution v2 assay detected fetal chromosomal aneuploidies across a range of fetal fractions with high sensitivities and specificities observed based on known clinical outcomes, a high overall PPV, and a low failure rate.