***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: OBJECTIVE To examine the relationship of early human embryonic development with the level of reactive oxygen species ( ROS ) in the culture media on the first day ( day 1 ROS ) after insemination . DESIGN A prospect i ve study . SETTING Patients undergoing assisted reproduction in a teaching hospital . PATIENT(S ) Patients undergoing conventional IVF ( n = 104 ; 115 cycles ) and intracytoplasmic sperm injection ( ICSI ) ( n = 91 ; 96 cycles ) were included . Both fertilization and early cultures were performed in human tubal fluid with 5 % serum substitute supplement . INTERVENTION(S ) Day 1 ROS levels in the central well ( sample ) and the outer well ( control ) of each embryo culture dish were measured after overnight incubation by chemiluminescence assay using luminol as the probe . MAIN OUTCOME MEASURE(S ) Fertilization rate and embryo quality at day 3 and 5 were recorded for each cycle . Age , parity , and demographic features were also compared . RESULT ( S ) High day 1 ROS levels in culture media were associated with low blastocyst rate , low fertilization rate , low cleavage rate , and high embryonic fragmentation with ICSI but not with conventional IVF . High day 1 ROS levels in culture media were associated with lower pregnancy rates in both IVF and ICSI cycles . CONCLUSION ( S ) Reactive oxygen species generated in culture media by day 1 may be an important biochemical marker for early embryonic growth . Increased embryonic fragmentation and slow cleavage rate may be partially attributed to early exposure of embryos to high ROS levels in ICSI cycles . Differential growth of ICSI embryos incubated under identical conditions may be in part due to differences in ROS levels of the culture medium surrounding these embryos 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 OBJECTIVE To examine the effects of increased sperm DNA damage in relation to seminal oxidative stress in men with idiopathic and male factor infertility . Prospect i ve study . SETTING S Infertility clinic at a tertiary care academic institution . PATIENT(S ) Ninety-two infertile men with normal female partners . Sixteen fertile donors served as the control group . INTERVENTION(S ) St and ard semen analysis and assessment of levels of seminal oxidative stress . Assisted reproductive techniques in 33 of the 92 patients ( IUI [ n = 19 ] , IVF [ n = 10 ] , and intracytoplasmic sperm injection [ n = 4 ] ) . MAIN OUTCOME MEASURE(S ) Sperm DNA damage by sperm chromatin structure assay . Results were expressed as DNA fragmentation index . RESULT ( S ) Patients were classified as having either idiopathic ( n = 23 ) or male factor infertility ( n = 69 ) . Patients with idiopathic and male factor infertility had significantly higher DNA fragmentation index and oxidative stress compared with the case of fertile donors . A clinical pregnancy was achieved in 9 ( 27 % ) of 33 patients with assisted reproductive techniques . Significantly higher DNA fragmentation index and oxidative stress were found in men who failed to initiate a pregnancy after assisted reproductive techniques ( n = 24 ) , compared with the cases of those who succeeded and of the fertile donors . DNA fragmentation index was correlated positively with oxidative stress ( r = 0.27 ) , and negatively with fertilization ( r = -0.70 ) and embryo quality ( r = -0.70 ) . CONCLUSION ( S ) Sperm DNA damage is significantly increased in men with idiopathic and male factor infertility and in men who failed to initiate a pregnancy after assisted reproductive techniques . Such an increase may be related to high levels of seminal oxidative stress 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 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 evaluate sperm DNA fragmentation and semen parameters to diagnose male factor infertility and predict pregnancy after IVF . DESIGN Prospect i ve study . SETTING Academic research laboratory . PATIENT(S ) Seventy-five couples undergoing IVF and 28 fertile donors . INTERVENTION(S ) Sperm DNA fragmentation was measured by the alkaline Comet assay in semen and sperm after density gradient centrifugation ( DGC ) . Binary logistic regression was used to analyze odds ratios ( OR ) and relative risks ( RR ) for IVF outcomes . MAIN OUTCOME MEASURE(S ) Semen parameters and sperm DNA fragmentation in semen and DGC sperm compared with fertilization rates , embryo quality , and pregnancy . RESULT ( S ) Men with  sperm DNA fragmentation  at more than a diagnostic threshold of 25 % had a high risk of infertility ( OR : 117.33 , 95 % confidence interval [ CI ] : 12.72 - 2,731.84 , RR : 8.75 ) . Fertilization rates and embryo quality decreased as sperm DNA fragmentation increased in semen and DGC sperm . The risk of failure to achieve a pregnancy increased when sperm DNA fragmentation exceeded a prognostic threshold value of 52 % for semen ( OR : 76.00 , CI : 8.69 - 1,714.44 , RR : 4.75 ) and 42 % for DGC sperm ( OR : 24.18 , CI : 2. 
    Output:
    
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 .