Preimplantation genetic testing is not a preferred recommendation for patients with X chromosome abnormalities

Abstract

STUDY QUESTION: Should women with X chromosome abnormalities (XCAs) be recommended to have embryos selected by both morphological and cytogenetic assessment through preimplantation genetic testing (PGT) rather than morphological assessment only in conventional IVF/ICSI treatment? SUMMARY ANSWER: PGT is not a preferred recommendation for women with XCAs in the absence of other PGT indications. WHAT IS KNOWN ALREADY: XCAs are the most frequent sort of chromosomal aberrations in infertile women. Patients with a complete or partial absence of one X chromosome, diagnosed as Turner Syndrome (TS), demonstrate low spontaneous pregnancy rates (5-7%) and high miscarriage rates (22.8-30.8%), as well as high chances of birth defects (20%). PGT is known to improve pregnancy rates and decrease the incidence of miscarriage in couples with chromosomal aberrations such as Robertsonian and reciprocal translocations and Klinefelter Syndrome. STUDY DESIGN, SIZE, DURATION: A retrospective cohort study was conducted with 394 women with XCAs and undergoing their first oocyte retrieval and first embryo transfer cycle from June 2011 to August 2019 in the Reproductive Hospital Affiliated to Shandong University. PARTICIPANTS/MATERIALS, SETTING, METHODS: Pregnancy outcomes were compared between the conventional IVF/ICSI group (n=284) and the PGT group (n=110) in the first fresh or frozen embryo transfer cycle for each woman with XCAs. Three platforms were applied in PGT: fluorescence in situ hybridisation (FISH, n=34), array comparative genomic hybridisation (aCGH, n=24) and next-generation sequencing (NGS, n=51). The embryo aneuploidy rate and distribution of embryonic chromosomal aberrations revealed by aCGH or NGS were analysed and stratified by maternal age and type of XCAs to assess the effect of maternal XCAs on embryo karyotypes. MAIN RESULT AND THE ROLE OF CHANCE: The live birth rate (LBR) per embryo transfer was similar between the PGT group and IVF/ICSI group both in the first cycle of fresh or frozen embryo transfer respectively (39.13% in PGTFISH vs 42.58% in IVF/ICSI, Padj=0.558; 66.67% in PGTFISH vs 52.08% in PGTaCGH/NGS vs 53.06% in IVF/ICSI, Padj=0.756), as was the clinical pregnancy rate (60.87% in PGTFISH vs 50.97% in IVF/ICSI, Padj =0.672; 88.89% in PGTFISH vs 58.33% in PGTaCGH/NGS vs 69.39% in IVF/ICSI, Padj =0.480) and the pregnancy loss rate (35.71% in PGTFISH vs 16.46% in IVF/ICSI, Padj =0.136; 12.50% in PGTFISH vs 10.71% in PGTaCGH/NGS vs 23.53% in IVF/ICSI, Padj =0.352). The rates of maternal and neonatal complications were also comparable between the PGT and IVF/ICSI groups with fresh and frozen transfers respectively (10.00% vs 8.85%, P=1.000; 21.74% vs 14.55%, P=0.272). Intriguingly, the distribution of embryonic chromosome abnormalities was more frequent on autosomes 22 (20.39%), 21 (18.45%) and 16 (17.47%), compared with the X chromosome (8.73%). LIMITATIONS, REASONS FOR CAUTION: Selection bias is an inherent drawback of a retrospective study. First, our participants hosted 4.84% X chromosome mosaicism with few typical somatic anomalies of TS. Second, the incidences of history of recurrent miscarriage and abnormal offspring in the PGT group were higher than in IVF/ICSI group although binary logistic regression analysis was performed to attenuate the modifying effect of confounding factors. Third, FISH performed in this study only used X/Y probes and lacked the reference of autosome, which might have resulted in misdiagnosis and bias. Finally, intrinsic disadvantages could not be totally avoided due to the retrospective nature of this study. WIDER IMPLICATION OF THE FINDINGS: In the current study, comparable pregnancy outcomes were revealed among a large cohort of women with XCAs undergoing their first cycles of PGT or conventional IVF/ICSI treatment. Moreover, the X chromosome abnormality was illustrated to cause no higher frequency of aberrations in embryos. Our data provided perspectives for genetic and reproductive counselling to XCAs individuals and their families.