Effects of reducing insemination time in human in vitro fertilization and embryo development by using sibling oocytes. Prolonged sperm-oocyte exposure and high sperm concentration affect human embryo viability and pregnancy rate. Shortened exposure of oocytes to spermatozoa improves in-vitro fertilization outcome: a prospective, randomized, controlled study. A prospective randomized controlled study of the effect of short coincubation of gametes during insemination on zona pellucida thickness. The effects of brief gamete co-incubation in human in vitro fertilization. Short coincubation of gametes in in vitro fertilization improves implantation and pregnancy rates: a prospective, randomized, controlled study. Extending the coincubation time of gametes improves in vitro fertilization.
Recent studies showed a beneficial effect of reducing the time of sperm-oocyte interaction on fertilization, division, and implantation rates of the oocytes obtained from randomized patients. In the present study, the effects of reduced insemination time on fertilization and embryo development were evaluated by using sibling oocytes from the same patient.
                A total of 464 oocytes from 36 patients was randomly allocated to be inseminated for either 1 hr (reduced) or 18 hr (regular).
                Fertilization rates were not significantly different between reduced (135/229; 59%) and regular (150/235; 64%) groups. Cleavage rates and embryo quality were similar in both groups. A total of 135 embryos (73 from the reduced and 62 from the regular group) was transferred to 36 patients. Thirty-four embryos implanted in 18 patients (25.2% implantation and 50.0% pregnancy rates).
                Fertilization, cleavage, and embryo development from 1-hr insemination is comparable, not superior, to those from an 18-hr insemination time, which is commonly used in in vitro fertilization programs. These data suggest that reduced insemination time can be used during in vitro fertilization to avoid unnecessarily longer exposure to spermatozoa. 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. A prospective, randomized study of 158 patients undergoing in-vitro fertilization (IVF) and embryo transfer was conducted to evaluate whether a shortened exposure of oocytes to spermatozoa enhances oocyte development, and subsequently influences the IVF outcome. A comparison was made between conventional treatment time and shorter exposure of retrieved oocytes to spermatozoa. Fertilization and cleavage rates, embryo quality, implantation and pregnancy rates in the study group (short exposure) versus controls (standard IVF procedure) were evaluated. Fertilization (56 versus 61%) and cleavage rates (96 versus 92%) were similar in the two groups respectively. However, embryo quality was significantly higher in the study group (P < 0.05). Moreover, the pregnancy and implantation rates were significantly increased (42.4 versus 26% per embryo transfer, and 16 versus 10% respectively; P < 0.05). Our results demonstrated that shorter exposure of oocytes to spermatozoa is superior to the standard time in IVF and may have a favourable effect on implantation rates by improving embryo quality. A prospective, randomized study was conducted to evaluate the thickness, of zona pellucida (ZP) after brief or standard exposure of human oocytes to spermatozoa, and to determine the correlation between ZP thickness, fertilization rate and embryo quality. The mean ZP thickness 48 h after insemination was found to be significantly less in fertilized oocytes than in non-fertilized oocytes in all treated groups (13.72 +/- 3.0 microns and 15.08 +/- 2.5 microns, respectively; p < 0.007). Zona pellucida thickness correlated positively with embryo quality. Brief exposure of gametes was found to influence ZP thickness. The ZP was significantly thinner after brief and intracytoplasmic sperm injection (ICSI) exposure of oocytes to spermatozoa than after standard in vitro fertilization (IVF). The mean ZP thickness 24 and 48 h after fertilization was significantly greater in standard IVF (16.43 +/- 2.8 microns and 15.22 +/- 2.7 microns, respectively) than in either the brief exposure or ICSI groups (12.78 +/- 2.4 microns and 13.01 +/- 3.5 microns vs. 13.46 +/- 2.2 microns and 13.16 +/- 2.4 microns; p < 0.0001). To investigate whether very short exposure of mature oocytes to sperm in vitro may affect the fertilization rates, embryo cleavage rates, and embryo quality between sibling oocytes in the same patient.
                Sibling oocytes of the same patient from 23 oocyte collection cycles were randomly allocated to the study group, with a 1-hr or 3-hr sperm-oocyte incubation, or the control group with the standard overnight gamete co-incubation. The fertilization rates, cleavage rates, and subsequent embryo quality were evaluated.
                Our results showed no statistically significant differences in fertilization rates, embryo cleavage rates, and quality of the embryos between the study group and the control group.
                Since the present study showed that long exposure of the oocyte to sperm has no advantage over short exposure, we prefer shortening the oocyte-sperm incubation period for reducing the negative effect induced by nonphysiologically high concentrations of spermatozoa. To examine the benefits of short coincubation of gametes compared to prolonged incubation in in vitro fertilization (IVF).
                Prospective randomized controlled study.
                Hospital-based fertility center.
                One hundred thirty patients (group 1) and 129 patients (group 2).
                Oocytes from group 1 were exposed to spermatozoa for 2 hours, and oocytes from group 2 were exposed to spermatozoa for 20 hours.
                Fertilization and cleavage rates, embryo quality, and pregnancy and implantation rates were evaluated. Estradiol (E(2)) and progesterone (P(4)) levels were measured in the wells of culture dishes after 2-hour exposure of oocytes/zygotes to spermatozoa in group 1 and after 20-hour exposure in both the groups.
                There was no difference between the two groups in the fertilization rate and the number of embryos obtained. However, the proportion of grade 1 embryos was significantly higher among group 1 compared to group 2 patients. Clinical pregnancy and implantation rates were significantly higher among group 1 compared to group 2. The significantly higher levels of E(2) and P(4) in the 20-hour cultures compared with the 2-hour cultures may have been detrimental to embryo quality, pregnancy, and implantation rates.
                Coincubation of gametes for 2 hours with standard or high insemination concentrations of spermatozoa significantly improved embryo quality and the pregnancy and implantation rates compared with overnight incubation of gametes. nan
This review has provided evidence that brief co-incubation of sperm and oocytes may improve the ongoing pregnancy and clinical pregnancy rates for infertile women undergoing IVF cycles. More RCTs are required to assess whether brief co-incubation would contribute to a higher live birth rate and a lower miscarriage rate compared to the standard overnight insemination protocol.