Abstract
Study question
Does sperm DNA fragmentation (SDF) reduce the ratio of good-quality embryos in day 3 (D3) and day 5 (D5) of embryonic development?
Summary answer
High sperm DNA fragmentation (SDF >15%) is associated with poor embryo quality at blastocyst-stage per cycle in unselected patients undergoing IVF and ICSI.
What is known already
It has been shown that the proportion of spermatozoa with DNA fragmentation is higher in infertile men than in semen from fertile men. However, the controversy regarding the impact that sperm genome damage can have on IVF or ICSI treatments is evident in the published literature. The effects of SDF would become evident after activation of the embryonic genome at 8-cell stage, compromising not only the quality of the embryos obtained, but also the reproductive outcomes, as reduced implantation rates, higher miscarriages rates and thus, a decreased chance of pregnancy.
Study design, size, duration
This multicentric observational retrospective study included 1339 couples who underwent 2759 IVF-ICSI cycles using autologous oocytes from January 2000 to March 2019. All men have an SDF test in their ejaculated spermatozoa by TUNEL assay (Terminal deoxynucleotidyl transferase dUTP nick end labeling). The subjects were divided into two groups according to their sperm DNA integrity: low (≤15%) (n = 2287 cycles) or high (>15%) (n = 472) SDF.
Participants/materials, setting, methods
Embryo quality was assessed complying morphological standards at cleavage-stage on D3 and at blastocyst-stage on D5 (inner cell mass (ICM) and trophectoderm (TE) grade (A, B, C or D)) in according to ASEBIR’s embryo selection criteria, being embryos of good quality those categorized as A+B. The outcomes were calculated in relation to the total number of zygotes obtained. The results were compared by Student t test; p value <0.05 was considered significant.
Main results and the role of chance
The SDF average of the low group was 5.8% (95% CI 5.6–5.9) whereas in high group was 23.7% (95% CI 23.0–24.4). The female age was equal, 37.1 years (95%CI 37.0–37.2) and 37.1 years (95% CI 36.8–37.4) respectively. A total of 9796 embryos were evaluated. The optimal cleavage-stage embryo rate per cycle was 25.0% (95% CI 21.7–28.3) (8.0 average cells number, 1.5 embryo fragmentation average, symmetry 1, mononucleated cells) versus 26.7% (95%CI 19.1–34.2) (7.9 average cells number, 1.8 embryo fragmentation average, symmetry 1, mononucleated cells) when comparing between groups (p < 0.001). Blastocyst-stage arrival rate (number of embryos at D5) per cycle was 55.8% (95% CI 54.3–57.2) in ≤ 15% SDF group (embryo quality score was ICM A:12.1%, B:69.5%, C:8.8%, D:4.5%; TE A: 7.5%, B:42.2%, C:42.2%, D:8.1%) and 55.9% (95% CI 52.8–59.1) in the >15% SDF group (ICM A:12.0%, B:68.7%, C:10.6%, D: 5.2%; TE A:9.1%, B:44.8%, C:37.8%, D:8.3%) (p < 0.001). The good quality blastocyst rate per cycle was significantly higher in the group with SDF ≤15%, 27.7% (95%CI 26.5–29.0) versus SDF >15% (27.4% (95%CI 24.6–30.2)). Of the total number of blastocysts, the proportion of A+B blastocyst was 60.5% (95% CI 58.3–62.7) and 64.2% (95% CI 59.2–69.2) (p < 0.001), respectively.
Limitations, reasons for caution
The retrospective and multicenter nature of this study leads to uncontrolled biases derived from the clinical practice. Although the results were not adjusted for female’s age, it was not statistically different between groups. Embryo morphology evaluation was performed by senior embryologists, it still remains a subjective evaluation, though.
Wider implications of the findings: In this study, a higher amount of data was compiled so that a large number of embryos were analyzed. The DNA integrity of the sperm may be an important consideration when poor quality embryos were obtained in the previous cycle when deciding on the next clinical strategy to apply.
Trial registration number
NA
A cost for high levels of sperm competition in rodents: increased sperm DNA fragmentation
