Estimation on risk of spontaneous abortions by genomic disorders from a meta-analysis of microarray results on large case series of pregnancy losses

A cohort study of neurodevelopmental disorders and/or congenital anomalies using high resolution chromosomal microarrays in southern Brazil highlighting the significance of ASD

Chromosomal microarray (CMA) is the reference in evaluation of copy number variations (CNVs) in individuals with neurodevelopmental disorders (NDDs), such as intellectual disability (ID) and/or autism spectrum disorder (ASD), which affect around 3-4% of the world's population. Modern platforms for CMA, also include probes for single nucleotide polymorphisms (SNPs) that detect homozygous regions in the genome, such as long contiguous stretches of homozygosity (LCSH). These regions result from complete or segmental chromosomal homozygosis and may be indicative of uniparental disomy (UPD), inbreeding, population characteristics, as well as replicative DNA repair events. In this retrospective study, we analyzed CMA reading files requested by geneticists and neurologists for diagnostic purposes along with available clinical data. Our objectives were interpreting CNVs and assess the frequencies and implications of LCSH detected by Affymetrix CytoScan HD (41%) or 750K (59%) platforms in 1012 patients from the south of Brazil. The patients were mainly children with NDDs and/or congenital anomalies (CAs). A total of 206 CNVs, comprising 132 deletions and 74 duplications, interpreted as pathogenic, were found in 17% of the patients in the cohort and across all chromosomes. Additionally, 12% presented rare variants of uncertain clinical significance, including LPCNVs, as the only clinically relevant CNV. Within the realm of NDDs, ASD carries a particular importance, owing to its escalating prevalence and its growing repercussions for individuals, families, and communities. ASD was one clinical phenotype, if not the main reason for referral to testing, for about one-third of the cohort, and these patients were further analyzed as a sub-cohort. Considering only the patients with ASD, the diagnostic rate was 10%, within the range reported in the literature (8-21%). It was higher (16%) when associated with dysmorphic features and lower (7%) for "isolated" ASD (without ID and without dysmorphic features). In 953 CMAs of the whole cohort, LCSH (≥ 3 Mbp) were analyzed not only for their potential pathogenic significance but were also explored to identify common LCSH in the South Brazilians population. CMA revealed at least one LCSH in 91% of the patients. For about 11.5% of patients, the LCSH suggested consanguinity from the first to the fifth degree, with a greater probability of clinical impact, and in 2.8%, they revealed a putative UPD. LCSH found at a frequency of 5% or more were considered common LCSH in the general population, allowing us to delineate 10 regions as potentially representing ancestral haplotypes of neglectable clinical significance. The main referrals for CMA were developmental delay (56%), ID (33%), ASD (33%) and syndromic features (56%). Some phenotypes in this population may be predictive of a higher probability of indicating a carrier of a pathogenic CNV. Here, we present the largest report of CMA data in a cohort with NDDs and/or CAs from the South of Brazil. We characterize the rare CNVs found along with the main phenotypes presented by each patient and show the importance and usefulness of LCSH interpretation in CMA results that incorporate SNPs, as well as we illustrate the value of CMA to investigate CNV in ASD.

The impact of air pollutants on spontaneous abortion: a case-control study in Tongchuan City

OBJECTIVES

Studies related to air pollutants and spontaneous abortion in urban northwestern China are scarce, and the main exposure windows of pollutants acting on pregnant women are unclear.

STUDY DESIGN

Case-control study.

METHODS

Data were collected from pregnant women in Tongchuan City from 2018 to 2019. A total of 289 cases of spontaneous abortion and 1156 cases of full-term labor were included and analyzed using a case-control study. Logistic regression models were developed to explore the relationship between air pollutants and spontaneous abortion after Chi square analysis and Air pollutant description.

RESULTS

O3 (odds ratio [OR] = 1.028) is a risk factor for spontaneous abortion throughout pregnancy. PM2.5 (OR = 1.015), PM10 (OR = 1.010), SO2 (OR = 1.026), and NO2 (OR = 1.028) are risk factors for spontaneous abortion in the 30 days before the last menstrual period. PM2.5 (OR = 1.015), PM10 (OR = 1.013), SO2 (OR = 1.036), and NO2 (OR = 1.033) are risk factors for spontaneous abortion in the 30-60 days before the last menstrual period. PM2.5 (OR = 1.028), PM10 (OR = 1.013), SO2 (OR = 1.035), and NO2 (OR = 1.059) are risk factors for spontaneous abortion in the 60-90 days before the last menstrual period.

CONCLUSION

Exposure to high levels of air pollutants may be a cause of increased risk of spontaneous abortion, especially in the first trimester of the last menstrual period.

Patterns of Cytogenomic Findings from a Case Series of Recurrent Pregnancy Loss Provide Insight into the Extent of Genetic Defects Causing Miscarriages

Background  A retrospective study was performed to evaluate the patterns of cytogenomic findings detected from a case series of products of conception (POC) in recurrent pregnancy loss (RPL) over a 16-year period from 2007 to 2023. Results  This case series of RPL was divided into a single analysis (SA) group of 266 women and a consecutive analysis (CA) group of 225 women with two to three miscarriages analyzed. Of the 269 POC from the SA group and the 469 POC from the CA group, a spectrum of cytogenomic abnormalities of simple aneuploidies, compound aneuploidies, polyploidies, and structural rearrangements/pathogenic copy number variants (pCNVs) were detected in 109 (41%) and 160 cases (34%), five (2%) and 11 cases (2%), 35 (13%) and 36 cases (8%), and 10 (4%) and 19 cases (4%), respectively. Patterns with recurrent normal karyotypes, alternating normal and abnormal karyotypes, and recurrent abnormal karyotypes were detected in 74 (33%), 71 (32%), and 80 (35%) of consecutive miscarriages, respectively. Repeat aneuploidies of monosomy X and trisomy 16, triploidy, and tetraploidy were detected in nine women. Conclusions  A comparable spectrum of cytogenomic abnormalities was noted in the SA and CA groups of RPL. A skewed likelihood of 2/3 for recurrent normal and abnormal karyotypes and 1/3 for alternating normal and abnormal karyotypes in consecutive miscarriages was observed. Routine cytogenetic analysis should be performed for consecutive miscarriages. Further genomic sequencing to search for detrimental and embryonic lethal variants causing miscarriages and pathogenic variants inducing aneuploidies and polyploidies should be considered for RPL with recurrent normal and abnormal karyotypes.

Genetic analysis of chorionic villus tissues in early missed abortions

Chromosomal abnormalities are the most common etiology of early spontaneous miscarriage. However, traditional karyotyping of chorionic villus samples (CVSs) is limited by cell culture and its low resolution. The objective of our study was to investigate the efficiency of molecular karyotyping technology for genetic diagnosis of early missed abortion tissues. Chromosome analysis of 1191 abortion CVSs in early pregnancy was conducted from August 2016 to June 2021; 463 cases were conducted via copy-number variations sequencing (CNV-seq)/quantitative fluorescent-polymerase chain reaction (QF-PCR) and 728 cases were conducted using SNP array. Clinically significant CNVs of CVSs were identified to clarify the cause of miscarriage and to guide the couples' subsequent pregnancies. Among these, 31 cases with significant maternal cell contamination were removed from the study. Among the remaining 1160 samples, 751 cases (64.7%) with genetic abnormalities were identified, of which, 531 (45.8%) were single aneuploidies, 31 (2.7%) were multiple aneuploidies, 50 (4.3%) were polyploidies, 54 (4.7%) were partial aneuploidies, 77 (6.6%) had submicroscopic CNVs (including 25 with clinically significant CNVs and 52 had variants of uncertain significance), and 8 cases (0.7%) were uniparental disomies. Our study suggests that both SNP array and CNV-seq/QF-PCR are reliable, robust, and high-resolution technologies for genetic diagnosis of miscarriage.

Prevalence of chromosomal alterations in first-trimester spontaneous pregnancy loss

Pregnancy loss is often caused by chromosomal abnormalities of the conceptus. The prevalence of these abnormalities and the allocation of (ab)normal cells in embryonic and placental lineages during intrauterine development remain elusive. In this study, we analyzed 1,745 spontaneous pregnancy losses and found that roughly half (50.4%) of the products of conception (POCs) were karyotypically abnormal, with maternal and paternal age independently contributing to the increased genomic aberration rate. We applied genome haplarithmisis to a subset of 94 pregnancy losses with normal parental and POC karyotypes. Genotyping of parental DNA as well as POC extra-embryonic mesoderm and chorionic villi DNA, representing embryonic and trophoblastic tissues, enabled characterization of the genomic landscape of both lineages. Of these pregnancy losses, 35.1% had chromosomal aberrations not previously detected by karyotyping, increasing the rate of aberrations of pregnancy losses to 67.8% by extrapolation. In contrast to viable pregnancies where mosaic chromosomal abnormalities are often restricted to chorionic villi, such as confined placental mosaicism, we found a higher degree of mosaic chromosomal imbalances in extra-embryonic mesoderm rather than chorionic villi. Our results stress the importance of scrutinizing the full allelic architecture of genomic abnormalities in pregnancy loss to improve clinical management and basic research of this devastating condition.