Complex chromosomal rearrangements in female carriers experiencing recurrent pregnancy loss or poor obstetric history and literature review

Purpose: Complex chromosomal rearrangements (CCRs) often remain unidentified as they are rarely observed in the general population. Females with CCRs are generally recognized on the identification of an affected child with multiple congenital anomalies (MCA) or having a history of repeated pregnancy loss/bad obstetric history (RPL/BOH). In contrast, males with CCRs are diagnosed primarily due to infertility. This study aimed to carry out a systematic epidemiological analysis of CCRs in one of the largest series from the Indian population. In addition, a review of the literature on female CCR carriers experiencing RPL/BOH has been compiled in an attempt to identify the genomic landscape of breakpoints, commonly involved chromosomes, and the breakpoint regions.

Methods: A total of 8560 healthy individuals with normal physical and mental well-being and had no history of any obvious genetic disorder at the time of presentation were referred for chromosome analysis in view of RPL/BOH between 1994 and 2024. Of them, 8158 had a normal chromosome complement whereas, 402 (4.7%) showed chromosomal aberrations. CCRs were detected in seven individuals, i.e., one partner in each of seven couples with structural rearrangements, all of whom were females. Comprehensive characterization of CCR was carried out using various molecular cytogenetic techniques.

Results: Seven CCR carriers had a total of 25 pregnancies: 20 leading to miscarriages (80%), one leading to the birth of an abnormal child (4%), two medically terminated pregnancies (8%) due to abnormal antenatal findings, and the remaining two were healthy (8%). A total of 13 different chromosomes with 24 non-recurring breakpoints were identified in these cases. Chromosome (#) 2 showed four breaks (16.7%), followed by #1, #4, #6, and #13 with three breaks each (12.5% each), while one break each (4.2% each) was seen on the remaining eight chromosomes (#3, #5, #8, #11, #14, #15, #17, and #21). Type I and type IV CCRs were observed in five (71.4%) and one case (14.3%), respectively, along with a "not a true" CCR (14.3%) in the present study group. Overall, the prevalence of CCRs in couples with RPL/BOH was 0.16%.

Conclusions: To the best of our knowledge, this is the first study on the epidemiology of CCRs in couples with RPL/BOH of Indian origin. The incidence of CCRs in couples experiencing RPL/BOH in the present cohort was found to be 0.16% with type I CCR being the most predominant of all types, which is congruent with observations from non-Hispanic white and South East Asian populations. The uniqueness and rarity of each CCR pose a challenge in genetic and reproductive counseling.