Influence of sperm quality on the development to blastocyst stage and its ploidy status

Study question: Does the sperm quality correlate with the ploidy status of the derived blastocysts? Summary answer: Blastocyst derived from poor quality sperm have the same probability to be euploid compared to ones formed from normal semen. What is known already: Thanks to the ICSI, in severe male factor infertility it becomes possible to offer IVF treatments, although extremely impaired sperm quality may have an impact on fertilization rates. Several study analyzing the clinical outcomes obtained with embryos derived from normal sperm samples compared to severe sperm morphology abnormalities, report very conflicting data. High rate of DNA fragmentation, mitochondrial dysfunction and chromosomal aneuploidy seem to be significantly higher in the spermatozoa from oligozoospermic and/or asthenozoospermic and/or teratozoospermic (OAT) males compared with unaffected controls. However, to date few data regarding the impact of the sperm quality on embryogenesis are reported. Study design, size, duration: This cohort retrospective study was performed from January 2014 to December 2015 on 148 Preimplantation Genetic Screening (PGS) cycles. The genetic outcome of 586 blastocysts were analyzed by mean of Whole Genome Amplification (WGA) and array-Comparative Genomic Hybridization (a-CGH). All mature oocytes retrieved were injected and cultured individually until the blastocyst stage at 37°C, 6%CO2, 5%O2. All biopsies were performed at blastocyst stage. Mean female and male ages were 34.95±4.5 and 38.05±5.9 years old, respectively. Participants/materials, setting, methods: All the patients enrolled in this study submitted to the following selection criteria: maternal age ≤36 years old, only standard ICSI to be performed, normal karyotype of both parents, genetic diseases and female infertility factors were excluded. All cycles were divided in 4 groups on the basis of semen parameters performed according to WHO 2010: group 1 normal; group 2 OAT ; group 3 severe OAT; group 4 NOA (Non-Obstructive Azospermia) and testis cancer patients. Main results and the role of chance: The number of cycles enrolled were 88, 53, 20, 18 in groups 1, 2, 3, 4, respectively. The number of oocytes injected were 775, 508, 180, 184 in groups 1, 2, 3, 4, respectively. There was no difference in fertilization rate between groups 2, 3, 4: 66.1% (336/508), 66.1% (119/180), 55.5% (120/184), respectively; a statistically higher (p<0.01) fertilization rate was found in group 1: 77.2% (598/775). The number of embryos obtained were 598, 336, 119, 120 in groups 1, 2, 3, 4, respectively. The blastocysts obtained were: 414 (69.2%), 241 (71.7%), 71 (59.7%), 62 (51.7%), respectively. The apparently lower blastocyst formation rate found in the group 4 compared to the other 3 groups does not reach a statistical significance, probably due to the low number of cycles enrolled in this group. Surprisingly, the rate of euploid/biopsied blastocysts was the same in all groups, even in number 4 in which sperms are recovered from testis: 45.5% (140/308), 53.8% (99/184), 58.6% (34/58) and 55.6% (20/36) in groups 1, 2, 3, 4, respectively. Pregnancy rates were 59.0% (46/78), 66.7% (30/45), 62.5% (10/16), 64.3% (9/14) in groups 1, 2, 3, 4, respectively (NS). Limitations, reasons for caution: The number of cycles eligible to be included in the study is still quite low, due to the strict inclusion criteria established in order to select male factor only patients; therefore, further cycles need to be performed to confirm these preliminary results. For that reason, the study is still ongoing. Wider implications of the findings: Our data gives strong hope to men with an extremely low semen quality. Due to the poor fertilization rate expected, it is advisable to increase the number of oocytes to inseminate and to extend the culture until the blastocyst stage since blastocysts euploidy probability is independent from the semen used.