Abstract
Objective To evaluate the influence of aspiration volume and final sperm position relative to the needle on fertilization and embryo development competence in ICSI. Methods A retrospective study analyzed 385 ICSI procedure videos, measuring distances between the needle bevel base and the sperm at oolemma breakage and needle withdrawal moments. Outcomes assessed were fertilization and blastulation rates. Results Blastulation rates did not significantly differ across aspiration volumes: <4 pl (50%), 4-8 pl (41.2%), 8-12 pl (47.2%), >12 pl (37.9%). Fertilization failure was higher (19.6%) when the sperm was near the needle bevel base at needle withdrawal compared to 2.4% when just behind the needle tip (p<0.0001). Fertilization rates were 66% with sperm in the needle trumpet vs. 85% outside (p=0.0017). Conclusions Blastulation rate was unaffected by aspiration volumes below 12 pl. Sperm positioned near the needle bevel base at withdrawal increased fertilization failure risk. Positioning sperm in the trumpet before withdrawal decreased fertilization rates. Further studies are needed to validate these findings across different settings.