***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: A prospect i ve , r and omized 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 ( st and ard 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 st and ard time in IVF and may have a favourable effect on implantation rates by improving embryo quality OBJECTIVE To confirm whether brief exposure of human oocytes to spermatozoa in vitro results in equivalent fertilization rates and possibly better quality embryos than overnight coincubation and to determine if there was a difference in outcome with regard to the type of culture medium used . DESIGN Prospect i ve distribution of gametes between treatments in sequential patients . SETTING Assisted reproductive technology program in private hospital . PATIENT(S ) Consecutively treated subfertile couples entering an infertility program . INTERVENTION(S ) Assisted reproductive technology treatment for infertility involving oocyte retrieval and in vitro fertilization . MAIN OUTCOME MEASURE(S ) When possible , the outcome of fertilization and embryo quality were compared when gametes were coincubated for 1 hour or overnight . Two different formulations of human tubal fluid were compared in some cases . RESULT ( S ) There was no statistically significant difference in fertilization rates between a brief or overnight coincubation of gametes or between the two treatment groups with regard to the type of culture medium used . The quality of the embryos was significantly better in the 1-hour exposure group . The embryos in Basal XI human tubal fluid medium were of significantly better morphological quality than their siblings in D3 + human tubal fluid medium . CONCLUSION ( S ) Coincubation of oocytes and spermatozoa for a shorter period produced embryos of superior morphological quality than the generally accepted overnight protocol . A simple glucose and phosphate-free human tubal fluid medium result ed in early cleavage embryos of better morphological quality than a medium supplemented with glucose , taurine , and glutathione Human oocyte development was evaluated after a reduced time exposure to spermatozoa in vitro .  A total of 119 patients were assigned to two study groups in a r and omized prospect i ve study in which each patient 's oocytes were exposed to spermatozoa for either 1 h ( group 1 - 58 patients ) or the st and ard 16 h incubation period ( group 2 - 61 patients ) . The fertilization rate obtained in group 1 was higher than in group 2 ( 285/393 , 73 % , and 272/410 , 66 % respectively ) , suggesting that the spermatozoa-oocyte interaction occurs within 1 h. This was confirmed in a study in vitro using fluorescently labelled spermatozoa and normal oocyte-cumulus complexes . Spermatozoa enter the cumulus complex within 15 min , traverse the cumulus layer within 3 h , and first appear in the oocyte cortex at 4 h post-insemination . The incidence of polyspermy was higher in oocytes exposed to spermatozoa for 16 h ( 3 % ) than for 1 h ( 1 % ) . There was no difference in the cleavage rate or morphological characteristics of embryos from both study groups . However , when evaluating the timing of embryo development , group 1 generated a significantly higher percentage of four to five cell embryos when compared to group 2 ( 55 versus 39 % ; P < 0.001 ) , documented at 40 h post-insemination . The implantation and pregnancy rates for group 1 were 11 and 28 % , while the corresponding rates for group 2 were 8 and 15 % . This suggests that a reduced exposure of oocyte to spermatozoa favours embryo viability , possibly due to a decrease in potential damage from sperm metabolic waste products Purpose : 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 r and omized 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 . Methods : A total of 464 oocytes from 36 patients was r and omly allocated to be inseminated for either 1 hr ( reduced ) or 18 hr ( regular ) . Results : 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 ) . Conclusions : 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 BACKGROUND Traditionally oocytes have been exposed to sperm overnight , for 16 - 20 h. This long period of co-incubation , however , has been shown to create problems with high levels of reactive oxygen species ( ROS ) , which may affect embryo viability and cause hardening of the zona pellucida . Recently , a positive effect of reducing the co-incubation time to 90 - 120 min was reported . The objective of this study was to evaluate whether a further reduction of the co-incubation period could benefit the outcome of IVF . METHODS In this prospect i ve study , 777 sibling oocytes from 81 women undergoing IVF were divided via alternate allocation to co-incubation for either 30 s ( ultrashort co-incubation ) ( group A ) or for 90 min ( st and ard co-incubation ) ( group B ) . Endpoints were normal fertilization ( two-pronuclear , 2PN ) , polyspermy ( > 2PN ) , embryo quality ( EQ ) , clinical pregnancy ( CP ) and implantation ( IR ) . RESULTS The normal fertilization rates of the two groups were comparable : group A 58.6 % versus group B 58.0 % . Significantly lower rates of polyspermy were seen in group A compared to group B ( 2.8 versus 7.2 % , P = 0.008 ) . No statistically significant differences in EQ , CP or IR were seen . CONCLUSION This is the first study demonstrating the achievement of good fertilization rates in IVF with ultrashort co-incubation . Significantly lower rates of polyspermy were seen in the group with ultrashort compared to the st and ard co-incubation group . Further studies are , however , needed in order to evaluate whether ultrashort co-incubation has any effect on the outcome of IVF Comparisons were made among techniques used to treat male factor infertility . Patients with semen quality below that recognized by World Health Organization criteria as normal had a better success rate when treated by gamete intrafallopian transfer than by in vitro fertilization ( 25 % v. 7 % pregnancy rate per patient ) . When < 2 x 10(6 ) motile sperm were recovered , the fertilization rate and embryo cleavage rate were higher for microdrop insemination than for conventional insemination . When 7000 - 370,000 motile sperm were recovered ,  microdrop insemination  result ed in a higher fertilization rate ( 46 % ) and a higher incidence of pregnancies ( 23 % of patients treated ) than subzonal sperm microinjection ( SUSM ) . However , for patients with 5000 - 50,000 motile sperm , the immediate transfer of SUSM oocytes to the Fallopian tube increased pregnancy rates for this technique to 24 % of patients treated . Direct microinjection of epididymal sperm from azoospermic men into the cytoplasm of oocytes result ed in pronuclear formation in 27 % of oocytes ; in comparison , pronuclear formation occurred in 5 % of SUSM oocytes . These data led to formulation of a logical treatment programme for male factor infertility Altering the coincubation time for spermatozoa and oocytes in vitro leads to varying results . Some authors suggest that longer exposure of spermatozoa to oocytes through coincubation is detrimental to fertilization and /or embryo development , possibly because of reactive oxygen species produced by the spermatozoa ( 1–5 ) . Other studies indicate that a decreased exposure time does not alter fertilization rates ( 3,6–9 ) and may even improve such rates ( 10–13 ) . In this report , we describe the results of our r and omized study on the effects of two coincubation times on in vitro fertilization ( IVF ) rates and embryo quality OBJECTIVE To examine the benefits of short coincubation of gametes compared to prolonged incubation in in vitro fertilization ( IVF ) . DESIGN Prospect i ve r and omized controlled study . SETTING Hospital-based fertility center . PATIENT(S ) One hundred thirty patients ( group 1 ) and 129 patients ( group 2 ) . INTERVENTION(S ) Oocytes from group 1 were exposed to spermatozoa for 2 hours , and oocytes from group 2 were exposed to spermatozoa for 20 hours . MAIN OUTCOME MEASURE(S ) 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 . RESULT ( S ) 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 . CONCLUSION ( S ) Coincubation of gametes for 2 hours with st and ard or high insemination concentrations of spermatozoa significantly improved embryo quality and the pregnancy and implantation rates compared with overnight incubation of gametes Purpose Evaluate the effect of short gamete incubation on fertilization rate and embryo quality . Methods A prospect i ve study has been performed . Two thous and five hundred and forty seven sibling oocytes from 240 couples undergoing IVF attempts were allocated to a short ( 1 h ) or a st and ard ( 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 st and ard 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 st and ard 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 st and ard 18 h insemination procedure Abstract Purpose : To investigate whether very short exposure ofmature oocytes to sperm in vitro may affect the fertilizationrates , embryo cleavage rates , and embryo quality betweensibling oocytes in the same patient . Methods : Sibling oocytes of the same patient from 23 oocyte collection cycles were r and omly allocated to the study group , with a 1-hr or 3-hr sperm — oocyte incubation , or the controlgroup with the st and ard overnight gamete co-incubation . The fertilization rates , cleavage rates , and subsequentembryo quality were evaluated . Results : Our results showed no statistically significant differencesin fertilization rates , embryo cleavage rates , and quality of the embryos between the study group and thecontrol group . Conclusions : Since the present study showed that long exposureof the oocyte to sperm has no advantage over shortexposure , we prefer shortening the oocyte — 
    Output:
    
Reduced gamete exposure time may be associated with beneficial outcomes .