Risk factors related to chromosomal mosaicism in human blastocysts.

RESEARCH QUESTION: Do factors relating to patients, ART, or both, affect the incidence of chromosomal mosaicism in human blastocysts? DESIGN: Blastocysts (n = 5718) from 1198 PGT-A cycles were biopsied between 2015 and 2021. All samples were amplified with multiple displacement amplification, and MiSeq system was used for next-generation sequencing. Mosaicism prevalence, and ART and patient factors potentially affecting mosaicism, were analysed. RESULTS: Among 5718 blastocysts detected, 1245 were mosaic (21.8%). Day-6 biopsied blastocysts yielded a statistically significantly higher mosaicism rate than day-5 blastocysts (24.5% versus 19.1%; OR 1.174; 95% CI 1.017 to 1.355, P = 0.028). Mosaicism rate increased as morphological score declined (excellent quality [13.2%], good quality [19.0%], average quality [22.0%] and poor quality [26.4%], P < 0.001). Compared with excellent-quality embryos, the OR of mosaicism was 1.490 (95% CI 1.069 to 2.078, P = 0.019) for good-quality, 1.751 (95% CI 1.274 to 2.407, P = 0.001) for average-quality, and 2.113 (95% CI 1.512 to 2.952, P < 0.001) for poor-quality embryos. Biopsy technicians were related to the incidence of mosaicism. One of the four technicians had a significantly higher mosaicism rate than the others (27.9%; 20.9%; 20.5%; 20.5%, respectively; P < 0.001). Parental ages, female BMI, history of infertility, sperm quality, antral follicular counts, ovarian stimulation protocols, stimulation length, total gonadotrophin dosage and number of retrieved oocytes, were not related to the incidence of mosaicism. CONCLUSION: Slow developing, poor-quality blastocysts are at higher risk of mosaicism. Biopsy technician may contribute to artificial mosaicism as an extrinsic factor.

Which type of chromosomal mosaicism is compatible for embryo transfer: a systematical review and meta-analysis.

PURPOSE: Chromosomal mosaicism becomes a common phenomenon in Preimplantaion genetic testing (PGT). This meta-analysis was conducted to study which feature of chromosomal mosaicism was compatible for embryo transfer. METHODS: After searching the database PubMed, Embase, CCTR and related reviews up until May 2021. Two reviewers extracted relevant information and assessed study quality by the Newcastle-Ottawa scale independently. Summary Odd Radios (OR) were calculated using fixed- or random-effects models for clinical outcomes. A network meta-analysis compared the clinical outcomes of different chromosomes. RESULTS: A total of six studies with 1,106 cycles of single mosaic embryo transferred were included. Significant results of implantation rate (IR), miscarriage rate (MR), and ongoing pregnancy/live birth rate (OP/LBR) were observed when comparing embryos with mosaicism level < 50% and ≥ 50% [OR 1.42, 95% CI (1.06, 1.89); OR 0.45, 95% CI (0.27, 0.75); OR 1.74, 95% CI (1.28, 2.37)], and embryos with mosaicism with only affecting segmental chromosome(s) and only involving whole chromosome(s) [OR 1.31, 95% CI (1.01, 1.71); OR 0.57, 95% CI (0.36, 0.93); OR 1.51, 95% CI (1.15, 2.00)]. Embryos with only mosaic gains or losses had significant higher IR and OP/LBR than complex mosaicism [Gains vs complex: OR 1.75, 95% CI (1.20, 2.54); OR 1.73, 95% CI (1.16, 2.58). Losses vs complex: OR 1.90, 95% CI (1.34, 2.71); OR 2.10, 95% CI (1.44, 3.07)]. Mosaic embryos with only one chromosome involved had significant favorable outcomes of IR and OP/LBR than with three or more chromosomes involved [OR 1.76, 95% CI (1.23, 2.52); OR 1.86, 95% CI (1.25,2.78)]. Chr. 7, Chr. 2, Chr. 1, Chr. 18, Chr. 11, Chr. X, Chr. 13, Chr. 14, Chr. 12, and Chr. 9 were considered as prioritized chromosomes of mosaic embryos for transfer. CONCLUSIONS: This analysis support the embryos with mosaicism level ≥ 50%, whole chromosome(s) involved, multiple mosaic abnormalities were associated with worse pregnancy outcomes. Mosaicism level of 50% could be used as a threshold to assess the mosaic embryos.

Identification of common genetic polymorphisms associated with down-regulated gonadotropin levels in an exome-wide association study.

OBJECTIVE: To investigate whether common genetic polymorphisms are associated with gonadotropin levels after down-regulation with daily gonadotropin-releasing hormone agonist and whether the polymorphisms of candidate variants influence the ovarian response to exogenous gonadotropins. DESIGN: Genetic association study. SETTING: University-affiliated in vitro fertilization center. PATIENTS: Subjects enrolled in an exploratory exome-wide association study (n = 862), a replication exome-wide association study (n = 86), and a classifier validation study (n = 148) were recruited from September 2016 to October 2018, September 2019 to September 2020, and January 2021 to December 2021, respectively. The included patients were aged ≤40 years and had a basal follicle-stimulating hormone (FSH) ≤12 IU/L. INTERVENTIONS: All participants received a luteal phase down-regulation long protocol. Genome DNA was extracted from the peripheral blood leukocytes. For the exploratory and replication cohorts, exome sequencing was conducted on a HiSeq 2500 sequencing platform. The multiplex polymerase chain reaction amplification technique and next-generation sequencing also were performed in the exploratory and replication cohorts. For the samples of the validation cohort, Sanger sequencing was performed. MAIN OUTCOME MEASURES: The primary endpoint was the gonadotropin levels after down-regulation, and the secondary endpoints were hormone levels and follicle diameters during stimulation, the total dose of FSH, duration of FSH stimulation, number of oocytes retrieved, and clinical pregnancy rate. RESULTS: In the exploratory cohort, we identified that FSHB rs6169 (P=2.71 × 10-24) and its single-nucleotide polymorphisms in high linkage disequilibrium were associated with the down-regulated FSH level. The same locus was confirmed in the replication cohort. Women carrying the C allele of FSHB rs6169 exhibited higher average estradiol level during stimulation (P=6.82 × 10-5), shorter duration of stimulation, and less amount of exogenous FSH (Pduration=0.0002; Pdose=0.0024). In the independent validation set, adding rs6169 genotypes into the prediction model for FSH level after down-regulation enhanced the area under the curve from 0.560 to 0.712 in a logistic regression model, and increased prediction accuracy by 41.05% when a support vector machine classifier was applied. CONCLUSION: The C allele of FSHB rs6169 is a susceptibility site for the relatively high level of FSH after down-regulation, which may be associated with increased ovarian FSH sensitivity.