Somatic chromosomal abnormalities in couples undergoing infertility treatment by intracytoplasmic sperm injection

[Systematic karyotyping before ICSI: A necessary procedure? Analysis of case studies in the Nancy University Hospital Fertility Centre]

INTRODUCTION

A constitutional karyotype is often assayed for the couple before ICSI management. The objective of this study was to assess the prevalence of chromosomal abnormality in an infertile population, the impact on the care of couples and its cost.

METHODS

A single-center retrospective study was carried out at the Fertility Center of the University Hospital of Nancy, including all infertile couples who underwent a karyotype analysis from June 2009 to December 2016.

RESULTS

1252 couples were included. 7.9% had at least one abnormal karyotype. A change in care affected 22% of these couples, i.e. 1.7% of the total population. 9% of couples with karyotype abnormality underwent PGD. In the male population, the percentage of abnormal spermograms is significantly higher in the group with karyotype abnormality compared to the control group (85.7% vs. 46.5%, P<0.001).

DISCUSSION

The constitutional karyotype, due to its high economic and human cost, and limited interest, is a screening method for chromosomal abnormalities that has no place systematically before performing IVF. The future lies in the restriction of the indications for prescribing the karyotype as well as in the realization of PGS in targeted situations.

Somatic/gonadal mosaicism for structural autosomal rearrangements: female predominance among carriers of gonadal mosaicism for unbalanced rearrangements

Background

Mosaicism for chromosomal structural rearrangements (Rea) is rare and the timing and mechanisms of mosaic Rea formation, maintenance, and clinical manifestation are poorly understood. To date, there are no published data on the cytogenetic profile of mosaic Reas. The question as to whether the proportion of abnormal cells in the carrier’s cultured blood is clinically significant remains unanswered. A previous study showed a strong female preponderance among carriers of mosaicism for Rea with pericentromeric breaks, indicating female-specific instability in early embryos. However, there is no corresponding study on male to female sex ratio (SR) among carriers of somatic and/or gonadal mosaicism for non-centromeric Rea. Population rates of mosaic Rea carriers calculated from consecutive series of patients referred for various reasons and from prenatal samples have not been established. Therefore the objectives of the present study were several-fold: (1) a study on profiles of Rea involved, (2) comparative analysis of the proportion of cells with unbalanced Rea in blood cultures from asymptomatic and affected carriers, (3) comparative analysis of SR in carriers of mosaicism for balanced and unbalanced Rea, and (4) determination of the population frequency of mosaicism for autosomal Rea.

Results

One hundred and three cases of mosaicism for autosomal non-centromeric Rea (N/Rea; normal line/structural rearrangement) in which the sex of the carrier had been specified were identified in the literature. Among balanced Rea, there was a prevalence of reciprocal translocations (89 %) over inversions (11 %). Among unbalanced Rea, deletions were the most frequent (40 %), followed by duplications (25 %) and rings (16 %). Derivatives and other chromosome abnormalities were less frequent (9 and 10 %). Eight of eleven (73 %) affected carriers of unbalanced Rea displayed a high proportion (>50 %) of abnormal cells compared to 4/37 (11 %) in asymptomatic carriers, p < 0.0001. Among carriers of mosaicism for balanced Rea there was a slight male predominance, 24 M/22 F, unlike the strong female predominance among carriers of mosaicism for unbalanced Rea, 11 M/46 F, p < 0.0001. Among ten carriers of unbalanced Rea with reproductive failure, only one was a male with infertility, and one was a partner of a woman experiencing recurrent spontaneous abortion. Population rates of mosaics for reciprocal translocaton (N/rcp), inversion (N/inv), and unbalanced Rea (N/unbal Rea) calculated from published data on consecutive series of patients with reproductive failures were 0.02 ‰, 0.005 ‰, and 0.002 ‰, correspondingly. Among 30,376 infertile patients three carriers of mosaicism for balanced Rea were identified (two cases of N/rcp and one case of N/inv), whereas among 26,384 patients with habitual abortion seven carriers were detected (five N/rcp and two N/inv). Among all 56,760 tested patients with reproductive failures only one was found to be a carrier of mosaicism for an unbalanced Rea (N/del, mosaicism for deletion).

Conclusions

A high proportion of Rea cells (>50 %) detected in cultured T-lymphocytes is associated with clinical manifestation of chromosomal imbalance. A strong female prevalence among carriers of mosaicism for unbalanced Rea suggests male-specific selection against abnormal cells rather than impairment of male gametogenesis, as the latter suggests a better prognosis for male fetuses. These findings should be taken into consideration when genetic counseling of patients referred after a diagnosis of mosaicism for an unbalanced rearrangement in a fetus.

Prevalence of chromosomal abnormalities in infertile couples in romania

The purpose of this study was to establish a correlation between the presence of chromosomal abnormalities in one of the partners and infertility. This retrospective study was performed at the Department of Reproductive Medicine, Life Memorial Hospital, Bucharest, Romania, between August 2007 to December 2011. Two thousand, one hundred and ninety-five patients with reproductive problems were investigated, and the frequency of chromosomal abnormalities was calculated. The control group consisting of 87 fertile persons who had two or more children, was investigated in this retrospective study. All the patients of this study were investigated by cytogenetic techniques and the results of the two groups were compared by a two-tailed Fisher's exact test. In this study, 94.99% patients had a normal karyotype and 5.01% had chromosomal abnormalities (numerical and structural chromosomal abnormalities). In the study group, numerical chromosomal abnormalities were detected in 1.14% of infertile men and 0.62% of infertile women, and structural chromosomal abnormalities were detected in 1.38% of infertile men and 1.87% of infertile women, respectively. The correlation between the incidence of chromosomal anomalies in the two sexes in couple with reproductive problems was not statistically significant. Recently, a possible association between infertility and chromosomal abnormalities with a significant statistical association has been reported. Our study shows that there is no association between chromosomal abnormalities and infertility, but this study needs to be confirmed with further investigations and a larger control group to establish the role of chromosomal abnormalities in the etiology of infertility.