Sperm retention site and its influence on cleavage rate and early development following intracytoplasmic sperm injection.
BACKGROUND
Intracytoplasmic sperm injection (ICSI) has risen to the forefront of reproductive technology. In the present study, the location of the sperm injection was noted, and a prospective study was conducted to evaluate the effect of the sperm retention site on cleavage rates and embryo quality after ICSI.


METHODS
This study involved 336 ICSI patients (age 27-44; average 37.4) where 1545 oocytes were observed. An oocyte was divided into nine sites and the sperm retention site was observed microscopically after injection. The polar body was placed at either the twelve or six o'clock position. The injection pipette was introduced at the three o'clock position and oolemma rupture was ascertained by mild suction. The main outcome measures were the relationship of sperm remaining in position in the oocyte to fertilization rate and embryo quality.


RESULTS
When the injection pipette was introduced at the three o'clock position, about 80% of the sperm remained in the center or left of center. The fertilization rate was significantly lower (p < 0.05) when the sperm remained near the site of introduction. Embryo quality was not significantly affected by the sperm retention site.


CONCLUSIONS
About 12-14% of the spermatozoa remained near the introducing position, and in these cases the fertilization rate was low. However, once fertilization occurred, the sperm retention site had minimal impact on embryo quality. Injecting sperm near the spindle site may improve embryo quality.
Yanaihara
Atsushi
A
Department of Obstetrics and Gynecology, Showa University School of Medicine, Tokyo, Japan. atsushi-y@med.showa-u.ac.jp
Iwasaki
Shinji
S
Negishi
Momoko
M
Okai
Takashi
T
D000328:Adult; D002970:Cleavage Stage, Ovum / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods*