The frequency of chromosomal abnormalities in patients with reproductive failure

Selected genetic causes of miscarriages

Approximately 15–25% of pregnancies end in spontaneous abortion, which is an expulsion from the mother body of the fetus weighing less than 500 g or before the 20th week of gestation. Determining abortions etiology is difficult due to its multifactorial character. Chromosomal abnormalities cause 38.6–80% of miscarriages. The largest group (93%) of chromosomal aberrations found in miscarried fetuses are numerical changes – aneuploidies and polyploidies. Much rarer (7%) are unbalanced structural aberrations, which can arise de novo or can be inherited from a carrier parent. In couples with spontaneous abortions, reciprocal chromosomal translocations (RCT) occur the most frequently, next are Robertsonian translocations and inversions. More complex chromosome abnormalities, e.g. double aneuploidies are found in 3.8% of fetuses. Another group of causes responsible for abortions are monogenic diseases of embryo or fetus resulting from autosomal dominant, autosomal recessive or X-linked mutations. Among mutations which may contribute to pregnancy loss are factor V Leiden gene mutations (c.1601G>A, earlier 1691G>A) and prothrombin gene mutation (c.97G>A, earlier 20210G>A). The research on mutations in candidate genes, eg.: ALOX15, CR1, CYP1A1, CYP17, CYP2D6, FOXP3, HLA-G, IL-6, KHDC3L, NLRP7, NOS3, PLK4, SYCP3, TLR3, TNF, TP53 and VEGFA is still ongoing.

A case–control study identifying the frequency and spectrum of chromosomal anomalies and variants in a cohort of 1000 couples with a known history of recurrent pregnancy loss in the Eastern region of India

Background:

Recurrent pregnancy loss (RPL) is a common occurrence that affects up to 15% of couples in their reproductive years. In both males and females with RPL and infertility, chromosomal abnormalities play a significant impact.

Aim:

The study was designed to examine the involvement of chromosomal anomalies and the frequency of certain chromosomal variants persistent among couples experiencing RPL.

Setting and Design:

This case–control study was conducted on 1000 couples from January 2015 to September 2020 in the state of Odisha, India, strictly adhering to principles of Helsinki Declaration (1975). The study was performed at the School of Biotechnology, KIIT University in collaboration with inDNA Life Sciences Private Limited.

Materials and Methods:

A cohort of 1148 individuals with a history of RPL were selected for the study and they were screened with respect to fertile controls for the presence of any chromosomal anomaly using G-banding, nucleolar organizing region (NOR)-banding and fluorescence in situ hybridisation wherever necessary.

Statistical Analysis:

The connection between distinct polymorphic variations and the occurrence of RPL was assessed using Fisher's exact test. Significant was defined as a P ≤ 0.005.

Results:

One hundred and thirty-four individuals were found to harbor chromosomal anomalies. This study elucidates that along with balanced chromosomal translocations, the involvement of polymorphic variants also plays a significant role in cases of RPL.

Conclusion:

The cumulative occurrence of chromosomal anomalies and variants across our cohort of 1148 individuals indicates that the chromosomal assessment of all couples experiencing RPL must be performed by all the clinicians. This study aids us in identifying chromosomal polymorphisms as major players of RPL in addition to novel chromosomal translocations.

Clinical Features of Infertile Men Carrying a Chromosome 9 Translocation

Previous studies indicated that chromosome 9 translocations are involved in reduced male fertility and increased chance of miscarriage in the female partner. The aim of this study was to review the clinical features and genetic counselling requirements of infertile men carrying chromosome 9 translocations. This study analyzed fertile-age male carriers of chromosome 9 translocations, and included 12 clinical cases in our hospital. In our cases, three cases had oligozoospermia or severe oligozoospermia, while nine cases had normal semen. Of the latter nine cases, seven were associated with recurrent spontaneous abortions, and two produced a phenotypically normal child as confirmed by amniocentesis. Male chromosome 9 translocations and specific breakpoints from reported papers were searched using PubMed and CNKI database. A literature review identified 76 male patients who carried chromosome 9 translocations. Breakpoints at 9p12, 9p11, 9p10 and 9q34.1 were related to pregestational infertility, while breakpoints at 9p21, 9q10, 9q11, 9q13, 9q21.1, 9q22, 9q22.2, 9q22.3, 9q34, 9q34.2 and 9q34.3 exhibited gestational infertility. Chromosome translocations involving chromosome 9 lead to increased risk of miscarriage. Carriers of chromosome 9 translocations should be counselled to consider in vitro fertilization accompanied by preimplantation genetic diagnosis.

Chromosomal Aberrations in Couples with Pregnancy Loss: A Retrospective Study

BACKGROUND

Recurrent pregnancy loss is a challenging reproductive problem, and chromosomal anomalies approximately affect 2%-8% of couples with recurrent pregnancy loss. The chromosomal abnormality, especially balanced translocation rearrangement in either parent, is the important cause of recurrent spontaneous abortion.

AIMS

The aim of this study was to investigate the role and prevalence of chromosomal anomalies in recurrent miscarriages. The results will be helpful for counseling and make the decision for alternative options and precaution for the affected couples and also support to make a national database.

SETTINGS AND DESIGN

The present retrospective study was carried out in 172 couples (344 individuals) having the history of three or more recurrent spontaneous abortion. The cytogenetic analysis was done in all 344 individuals using G-banding and karyotyping.

RESULTS

Out of 172 couples, 17 couples (9.88%) had different types of structural or numerical chromosomal abnormalities. The structural aberrations were observed in 15 (8.72%) couples, and numerical aberrations were seen in 2 (1.16%) couples. Out of 17 couples, 8 (47.05%) had balanced translocations, 2 (11.76%) had the Robertsonian translocation, 5 (29.41%) had the pericentric inversion of chromosome 8, 9, and Y, and only 2 (11.76%) women showed sex chromosome numerical aberrations.

CONCLUSIONS

Cytogenetic analysis should be an important routine investigation in couples with repeated miscarriages. Cytogenetic analysis is essential and helpful for genetic counseling to take precaution and implementing proper reproductive alternatives. Studies on the genetic basis of pregnancy loss should be taken up to generate data on these issues from different regions.

Subtelomeric Rearrangements in Patients with Recurrent Miscarriage

Background

The subtelomeric rearrangements are increasingly being investigated in cases of idiopathic intellectual disabilities (ID) and congenital abnormalities (CA) but are also thought to be responsible for unexplained recurrent miscarriage (RM). Such rearrangements can go unnoticed through conventional cytogenetic techniques and are undetectable even with high-resolution molecular cytogenetic techniques such as array comparative genomic hybridization (aCGH), especially when DNA of the stillbirth or families are not available. The aim of the study is to evaluate the rate of subtelomeric rearrangements in patients with RM.

Materials and Methods

In this cross-sectional study, fluorescent in situ hybridization (FISH), based on ToTelVysion telomeric probes, was undertaken for 21 clinically normal couples exhibiting a “normal” karyotype with at least two abortions. Approximately 62% had RM with a history of stillbirth or CA/ID while the other 38% had only RM.

Results

FISH detected one cryptic rearrangement between chromosomes 3q and 4p in the female partner of a couple (III:4) [46,XX,ish t(3;4)(q28-,p16+;p16-,q28+)(D3S4559+,D3S4560-,D4S3359+; D3S4560+, D4S3359- ,D4S2930+)] who presented a history of RM and family history of ID and CA. Analysis of the other family members of the woman showed that her sisters (III:6 and III:11) and brother (III:8) were also carriers of the same subtelomeric translocation t(3;4)(q28;p16).

Conclusion

We conclude that subtelomeric FISH should be undertaken in couples with RM especially those who not only have abortions but also have had at least one child with ID and/or CA, or other clinically recognizable syndromes. For balanced and cryptic anomalies, subtelomeric FISH still remains the most suitable and effective tool in characterising such chromosomal rearrangements in RM couples.

Clinical Features of Chromosome 6 Translocation in Male Carriers: A Report of 10 Cases and Review of the Literature

BACKGROUND The literature indicates that chromosome 6 is involved in balanced translocation and is involved in reproductive failure. This aim of this study was to explore the clinical features of chromosome 6 translocation in male carriers. MATERIAL AND METHODS We identified 10 patients who were carriers of chromosome 6 translocations and excluded the patients with varicocele, ejaculatory duct obstruction, and the other cause of infertility. The karyotype was analyzed using G-banding. A search for translocations on chromosome 6 involved in male infertility was performed using PubMed. We included cases of balanced chromosome 6 translocations involving adult men of fertile age and excluded those cases of live-born children, or those without breakpoints involving chromosome 6, or those with complex chromosomal translocations or chimeras. RESULTS All 10 patients underwent genetic counseling for infertility. Semen analysis showed that 1 case had azoospermia, while 9 cases exhibited normal semen criteria. The respective partners of the 9 cases with normal semen parameters had a tendency to miscarry: 3 experienced spontaneous and induced abortion because of abnormal embryos; 3 experienced 3 incidents of spontaneous abortion, 2 experienced double spontaneous abortion, and 1 experienced biochemical pregnancy on 3 occasions. Most of the chromosome 6 breakpoints in translocation carriers obtained by the PubMed search were associated with spontaneous abortion. CONCLUSIONS Chromosome translocations involving chromosome 6 influence fertility status and lead to increased risk of miscarriage. Cytogenetic screening before opting for assisted reproductive technology and the breakpoints of chromosome 6 translocation should be considered for infertile male carriers.

Chromosomal abnormalities in recurrent miscarriages by conventional karyotyping analysis

Abstract Objectives: to describe the prevalence and types of chromosomal abnormalities in couples with recurrent miscarriage and products of conception. Methods: electronic searches were performed in the PubMed/Medline database and in the Portal Regional da Biblioteca Virtual em Saúde/BVS (Regional Website of the Virtual Library in Health/BVS) using the descriptors “chromosomal abnormalities and abortions and prevalence”. After applying the inclusion and exclusion criterias, 17 studies were selected. Results: 11 studies were conducted in couples with recurrent miscarriage and six in products of conception. The main results of the couples with recurrent miscarriage were: the frequency of chromosomal abnormalities which varied from 1.23% to 12% and there was a predominance alteration of the chromosomal structures (reciprocal translocations, followed by Robertsonian). In products of conception, the results observed were: the frequency of chromosomal abnormality was above 50% in approximately 70% of the studies; there was a predominance alteration of the numerical chromosomal (trisomy - chromosomes 16, 18, 21 and 22, followed by polyploidy and monosomy X). Conclusions: in summary, cytogenetic alterations represent an importante cause of pregnancy loss and its detection can help couples with genetic counseling. Therefore, the value of knowledge on the prevalence of cytogenetic abnormalities in miscarriage samples is unquestionable, once it is permitted a proper genetic counseling for the couple.

Cytogenetic analysis in couples with recurrent miscarriages: a retrospective study from Punjab, north India

Human reproduction is considered as the most inefficient event as ~15-20% of human pregnancies end in miscarriage and in the product of miscarriages, chromosomal anomalies are a common occurrence. The aim of the present retrospective study was to assess the frequency of chromosomal aberrations in couples with recurrent miscarriages in the region of Punjab and to compare with worldwide frequencies. In this study, a total of 440 cases were referred between the period 1995-2015. After lymphocyte culturing, giemsa-trypsin banding was done for each case to assess the chromosomal anomalies. The frequency of chromosomal aberrations among couples was found to be 3.41% in our study. Among these aberrations, balanced reciprocal translocations formed the largest group with 60% anomalies. We would conclude that clinicians should understand the importance of chromosomal analysis in these couples and refer them for karyotyping after two miscarriages to rule out the possible genetic cause of recurrent miscarriages.

Evaluation of 1100 couples with recurrent pregnancy loss using conventional cytogenetic, PGD, and PGS: hype or hope

Recurrent pregnancy loss (RPL) is an important clinical problem, mostly resulting from chromosomal or genetic defects, while in 30-60% of cases, it is idiopathic. The aim of this study is to evaluate the frequency and types of chromosomal abnormalities, also pre-implantation genetic diagnosis (PGD) and pre-implantation genetic screening (PGS) outcomes among Iranian couples with RPL. This retrospective study was conducted on 1100 Iranian couples (2200 individuals) with RPL referred to Royan Institute between 2008 and 2014. Karyotyping had been performed using standard cytogenetic techniques. PGD results of RPL patients with abnormal karyotypes and PGS results of RPL patients with normal karyotypes were also analyzed. The frequency of chromosomal abnormalities in these patients was 4.95%. Women demonstrated more abnormalities (6.82%) in comparison to men (3.09%). The successful rate of pregnancy after PGD and PGS was 52 and 18.64%, respectively. The observation of 4.95% chromosomal abnormalities among the patients with RPL could support this hypothesis that there is a direct relationship between chromosomal abnormalities and RPL. More than half of the patients who underwent PGD had successful pregnancy; therefore, this approach can improve the success rate of pregnancy in them. The results of PGS cycles showed that this technique could increase the live birth rate in RPL patients.

PGD for a complex chromosomal rearrangement by array comparative genomic hybridization

Patients carrying a chromosomal rearrangement (CR) have an increased risk for chromosomally unbalanced conceptions. Preimplantation genetic diagnosis (PGD) may avoid the transfer of embryos carrying unbalanced rearrangements, therefore increasing the chance of pregnancy. Only 7-12 loci can be screened by fluorescence in situ hybridization whereas microarray technology can detect genome-wide imbalances at the single cell level. We performed PGD for a CR carrier with karyotype 46,XY,ins(3;2)(p23;q23q14.2),t(6;14)(p12.2;q13) using array comparative genomic hybridization. Selection of embryos for transfer was only based on copy number status of the chromosomes involved in both rearrangements. In two ICSI-PGD cycles, nine and seven embryos were analysed by array, leaving three and one embryo(s) suitable for transfer, respectively. The sensitivity and specificity of single cell arrays was 100 and 88.8%, respectively. In both cycles a single embryo was transferred, resulting in pregnancy following the second cycle. The embryo giving rise to the pregnancy was normal/balanced for the insertion and translocation but carried a trisomy 8 and nullisomy 9 in one of the two biopsied blastomeres. After 7 weeks of pregnancy the couple miscarried. Genetic analysis following hystero-embryoscopy showed a diploid (90%)/tetraploid (10%) mosaic chorion, while the gestational sac was empty. No chromosome 8 aneuploidy was detected in the chorion, while 8% of the cells carried a monosomy for chromosome 9. In summary, we demonstrate the feasibility and determine the accuracy of single cell array technology to test against transmission of the unbalanced meiotic products that can derive from CRs. Our findings also demonstrate that the genomic constitution of extra-embryonic tissue cannot necessarily be predicted from the copy number status of a single blastomere.

A cytogenetic study of couples with repeated spontaneous abortions

BACKGROUND AND OBJECTIVE

The frequency of chromosomal aberrations in Iran is not definitely known. This study determined the frequency of chromosomal aberrations in a series of couples with two or more spontaneous abortions and compared the findings with that reported from other countries.

METHODS

This was a descriptive study conducted on 100 couples with recurrent abortions. Both partners were karyotyped as part of the primary investigation. Other probable causes of abortion were also investigated.

RESULTS

Chromosomal aberrations were found in 8 (8%) of the females and 5 (5%) of the males. The prevalence of chromosomal abnormalities was as follows: 4 (30.8%) balanced reciprocal translocations, 3 (23%) Robertsonian translocations, 3 (23%) pericentric inversions, 1 (7.7%) paracentric inversion, 1 (7.7%) chromosomal marker, and 1 (7.7%) polymorphism 9qh+.

CONCLUSIONS

The pattern of chromosomal aberrations was similar to that reported in other studies, but the prevalence of chromosomal aberrations was higher.