Abnormal sperm concentration and motility as well as advanced paternal age compromise early embryonic development but not pregnancy outcomes: a retrospective study of 1266 ICSI cycles.

Purpose: To investigate the effect of sperm concentration, motility and advanced paternal age on reproductive outcomes.

Methods: A retrospective analysis of 1266 intracytoplasmic sperm injection (ICSI) cycles between 2013 and 2017. The cohort was divided into four groups according to semen concentration based on the WHO criteria (2010): group A (conc. <1 M/ml), group B (1 ≤ conc. <5 M/ml), group C (5 ≤ conc. < 15 M/ml) and the control group D (conc. ≥15 M/ml). The primary outcome investigated was the blastulation rate. Secondary outcomes were fertilization rate, top quality blastocyst formation rate and ongoing pregnancy rate.

Results: After adjustment for maternal age and number of oocytes recovered, a significant difference was observed between group A and group D on the rate of fertilized oocytes [66.7 (40.0-80.0) vs 75.0 (57.1-90.2), adjusted p < 0.001] and the blastocyst formation rate [50.0 (33.3-66.3) vs 55.6 (40.0-75.0), adjusted p < 0.05]. However, the male factor did not affect the top quality blastocyst formation rate nor the ongoing pregnancy rate. Considering the age of the male partner as confounding factor, at the increase of each year of age, a reduction of 0.3% on the fertilization rate was observed but no other outcome was impacted. A negative correlation was also observed between sperm motility and fertilization rate in the group with a motility <5%.

Conclusion: Male factor infertility and advanced paternal age may compromise fertilization and blastulation rates but not top quality blastocyst formation rate or the establishment of pregnancy in ICSI cycles.