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 min of contact between oocytes and spermatozoa capacitated for 1 h. No fertilization occurred, whatever the duration of sperm capacitation, when gamete mixing did not exceed 30 min. 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.

Short gamete co-incubation during in vitro fertilization decreases the fertilization rate and does not improve embryo quality: a prospective auto controlled study

“…This result supports the data of previous studies [3][4][5][12][13][14][15] but is called into question by others [10,11,22], which have shown an improvement of the morphological embryo quality and of the pregnancy and implantation rates. The difference methods used for gamete co-incubation could explain these conflicting results.…”

“…However, several studies of gamete kinetic interaction in vivo have shown that (1) gamete contact and fertilization occur within 20 min post coitus in mammals [1,2] and (2) an average number of 15 spermatozoa are observed, in vitro, in the cumulus after 15 min of gamete contact. Furthermore, 80% of oocytes are fertilized after 1-h exposure to spermatozoa [3][4][5]. On the other hand, reactive oxygen species (ROS) released by the cellular metabolism have been implicated in (1) fatty acid peroxydation causing a decrease in membrane fluidity [6,7], (2) DNA fragmentation [8] and (3) embryo developmental arrest [9].…”

Effects of cumulus cells removal after 6 h co-incubation of gametes on the outcomes of human IVF

“…Short co-incubation of gametes has been performed routinely in our center since 2008. About 90% of fertilized oocytes released the second polar body at 6 h of insemination and 80% presented two pronuclei at 8 h of insemination [14][15][16][17]. We therefore chose a 6 h period of co-incubation.…”

The effect of two distinct levels of oxygen concentration on embryo development in a sibling oocyte study

“…Cleavage rate was defined as the total number of cleaved embryos from the total number of fertilized oocytes. Embryo quality was scored according to the presence of equal-sized blastomeres with no fragmentation (grade 1), <20 % fragmentation (grade 2), 20 %-50 % fragmentation (grade 3), and >50 % fragmentation (grade 4) [22] The grade was reduced by onehalf when embryos had unequal-sized blastomeres. A topquality embryo was defined as an 8-cell embryo grade 1 on day 3.…”