Prolonged sperm-oocyte exposure and high sperm concentration affect human embryo viability and pregnancy rate.
A reduced time interval of oocyte exposure to spermatozoa was investigated to assess whether it could enhance oocyte development and improve embryo viability, especially in cases of male factor infertility. A total of 167 patients were included in a prospective randomized study. They were randomly allocated to two major study groups, A (n = 85) and B (control group; n = 82). The oocytes from group A patients were exposed to spermatozoa for only 1 h; those from group B were exposed for 16 h. The two study groups were then subdivided according to semen quality for further analysis of the results. Significantly higher percentages were obtained in group A than in group B in terms of the fertilization rate (74 versus 68%, P < 0.025), cleavage rate (53 versus 41%, P < 0.005), pregnancy rate (27 versus 12%, P < 0.05) and implantation rate (11 versus 6%, P < 0.05). In addition, an increased fertilization rate was achieved in oocytes exposed to male factor spermatozoa for only 1 h compared with the conventional incubation period (78 versus 65%, P < 0.01). Advanced cellular stages (55 versus 41%, P < 0.02) and higher implantation rates (13 versus 4%, P < 0.05) were attained in the subgroup whose oocytes were exposed to normal spermatozoa for 1 h compared with the male factor spermatozoa with the standard culture interval. The higher fertilization rates, enhanced embryo development and viability achieved in group A indicate that prolonged exposure of oocytes to high concentrations of spermatozoa is detrimental, decreasing sperm-oocyte interaction and subsequent embryo implantation, particularly in male factor patients.
Gianaroli
L
L
SISMER, Medicine Reproductive Unit, Bologna, Italy.
Fiorentino
A
A
Magli
M C
MC
Ferraretti
A P
AP
Montanaro
N
N
D000328:Adult; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation; D010064:Embryo Implantation; D004622:Embryo, Mammalian / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D007248:Infertility, Male; D008297:Male; D011247:Pregnancy; D011446:Prospective Studies; D013076:Sperm Count; D013997:Time Factors