Timing of in-vitro fertilization of cumulus-free and cumulus-enclosed human oocytes

Abstract

In humans, in contrast to other species, sperm capacitation requires a very short time, as in-vitro fertilization has been obtained after only 45 mm of contact between oocytes and spermatozoa capacitated for 1 h. No fertilization occurred, whatever the duration of sperm capacit.ation, when gamete mixing did not exceed 30 mim. On the contrary, 85% of cumulus-free mature oocytes exposed to sperm for 1–4 h were fertilized. The presence of the pre-ovulatory, fully-expanded or compact cumulus mass did not represent a physical barrier to sperm progression, as we observed no delay in fertilization when oocytes were enclosed in the cumulus. The use of a short insemination protocol (1–4 h instead of 17–20 h) did not reduce the fertilization rate of denuded or cumulus-enclosed oocytes and had no significant effect on the morphological appearance of the embryos or their cleavage rates.