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

PURPOSE: Evaluate the effect of short gamete incubation on fertilization rate and embryo quality. METHODS: A prospective study has been performed. Two thousand five hundred and forty seven sibling oocytes from 240 couples undergoing IVF attempts were allocated to a short (1 h) or a standard (18 h) insemination procedure. Diploid fertilization rate (two pronuclei, 2PN), polyspermy (>2PN) and embryo quality were compared. RESULTS: The fertilization rate was statistically lower in the short insemination group compared to the standard insemination one (64.9% and 70.1%; P = 0.039), with a similar polyspermy rate observed between the two groups. A slight, but non significant, increase was observed concerning good embryo quality rate in the short insemination group when compared to the standard insemination, both at day 2 (60.1 vs. 58.1%; P = 0.06) and day 3 (53.2 vs. 48.5%; P = 0.22). CONCLUSION: This new study highlights that a 1 h gamete exposure decreases the fertilization rate and does not improve embryo quality compared with a standard 18 h insemination procedure.