***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: BACKGROUND Recently , advances in human  IVF-embryo transfer ( ET ) have been reported using sequential media and blastocyst stage ET . In our previous report , using a prospect i ve , r and omized study , no advantage was found using the blastocyst stage ET compared with day 3 ET . This study was performed in order to evaluate implantation and pregnancy rates of hatching blastocyst stage ET compared with conventional day 3 ET . METHODS AND RESULTS A total of 480 patient cycles were evaluated using a prospect i ve , r and omized study . The pregnancy rate and implantation rate were compared between the day 3 ET ( n = 240 ) and hatching blastocyst stage ET ( Hat ET ; n = 240 ) . The Hat ET group had a pregnancy rate of 29.3 % ( 55 out of 188 ) and an implantation rate of 21.4 % ( 67 out of 313 ) . The day 3 ET group had a pregnancy rate of 29.2 % ( 70 out of 240 ) and an implantation rate of 19.1 % ( 93 out of 488 ) . In the Hat ET group , the pregnancy rate , implantation rate and ongoing pregnancy rate of day 5 ET and day 6 ET were all higher than the respective rates in the day 7 - 9 ET group . CONCLUSION We found that the pregnancy rate and implantation rate of ET with hatching stage blastocysts had no advantage compared with the conventional day 3 ET OBJECTIVE : To evaluate the efficacy of blastocyst transfer in comparison with cleavage stage transfer . STUDY DESIGN : A r and omized , prospect i ve study was conducted in Infertility clinic , Department of Obstetrics and Gynecology , Mahatma G and hi Hospital , Jaipur on 300 patients aged 25 - 40 years undergoing in-vitro fertilization (IVF)/intra-cytoplasmic sperm injection ( ICSI ) cycle from May 2010-April 2011 . When three or more Grade -I embryos were observed on day 2 of culture , patients were divided r and omly into two study groups , cleavage stage transfer and blastocyst transfer group having 150 patients each . Primary outcomes evaluated were , Clinical pregnancy rate and Implantation rate . The results were analyzed using proportions , st and ard deviation and Chi-square test . RESULTS : Both the groups were similar for age , indication and number of embryos transferred . Clinical pregnancies after blastocyst transfer were significantly higher 66 ( 44.0 % ) compared to cleavage stage embryo transfer 44 ( 29.33 % ) ( P < 0.01 ) . Implantation rate for blastocyst transfer group was also significantly higher ( P < 0.001 ) . CONCLUSION : Blastocyst transfer having higher implantation rate and clinical pregnancy rate lead to reduction in multiple pregnancies OBJECTIVE To compare blastocyst-stage embryo transfers ( ETs ) with day 2 - 3 ETs in patients who failed to conceive in three or more day 2 - 3 IVF/ET cycles . DESIGN Prospect i ve , r and omized . SETTING Fertility unit in a university medical center . PATIENT(S ) Fifty-four patients with an adequate ovarian response underwent oocyte retrievals . The patients were prospect ively and r and omly divided into blastocyst-stage and day 2 - 3 ET groups . INTERVENTION(S ) Ovarian down-regulation was obtained using GnRH agonist , and controlled ovarian hyperstimulation was achieved using daily administration of gonadotropins . MAIN OUTCOME MEASURE(S ) The rate of blastocyst formation , ET cancellations , pregnancies , implantation , multiple gestation , and live births . RESULT ( S ) The clinical pregnancy rates per oocyte retrieval were 21.7 % and 12.9 % per blastocyst and day 2 - 3 ETs , respectively . Although there was a significantly higher implantation rate for blastocyst embryos ( 21.2 % ) as compared with 48- to 72-hour embryos ( 6 % ) , the multiple-pregnancy rate was not significantly different between both groups . An ET cancellation rate of 26 % and 6.4 % for blastocyst and day 2 - 3 ETs , respectively , was observed . The presence of two or more 8-cell embryos on day 3 in culture carried a high probability of obtaining blastocysts for transfer . CONCLUSION ( S ) This prospect i ve r and omized study suggests that in patients with an adequate ovarian response who failed to conceive in at least three IVF/ET cycles [ 1 ] . transfer of blastocyst-stage embryos carries a significantly higher implantation rate ; [ 2 ] . the pregnancy rate per oocyte retrieval and ET are higher in the blastocyst-stage group , even if it did not reach statistical significance ; [ 3 ] . a higher ET cancellation rate was observed in the whole blastocyst-stage group ; [ 4 ] . the ET cancellation rate was reduced significantly if the decision to proceed to blastocyst transfer was made on day 3 after oocyte retrieval , which is a post hoc conclusion BACKGROUND The respective advantages of day 3 and day 5 embryo transfer are a matter of debate . Previous comparisons did not include pronuclear stage zygote scoring and cumulative success rates ( fresh and cryopreserved embryos ) . METHODS Patients were r and omized prospect ively for day 3 or day 5 embryo transfer .  Day 3 embryos were selected for transfer and cryopreservation by using combined evaluation at the pronuclear and cleavage stages . RESULTS There was no difference between day 3 and day 5 fresh embryo transfers as to the rates of pregnancy ( 58 versus 62 % ) , clinical pregnancy ( 56 versus 58 % ) , delivery ( 50 versus 48 % ) , implantation ( 35 versus 38 % ) and birth ( 33 versus 36 % ) rates . The corresponding values for cryopreserved embryo transfers were also similar . However , day 3 embryo transfer compared favourably with day 5 transfer when the pregnancy ( 90 versus 66 % ) , clinical pregnancy ( 85 versus 62 % ) and delivery ( 77 versus 52 % ) rates were calculated per oocyte recovery attempt . CONCLUSIONS With a selected population of good prognosis patients and our embryo selection criteria , the implantation potential of day 3 and day 5 embryos is equal . Per oocyte recovery attempt , day 3 transfer is more clinical ly efficient than day 5 transfer , but at least one transfer of cryopreserved embryos is necessary to manifest this superiority The effectiveness of blastocyst culture and transfer in human in-vitro fertilization ( IVF ) was evaluated in a prospect i ve r and omized trial in patients having a moderate to good response to gonadotrophin stimulation . Embryos were transferred either on day 3 after culture to around the 8-cell stage in Ham 's F-10 medium supplemented with fetal cord serum , or on day 5 after culture to the blastocyst stage in the sequential serum-free media G 1.2 and G 2.2 . The pregnancy rates after transfer on day 3 or day 5 were equivalent , 66 and 71 % respectively ; however , significantly more embryos were transferred on day 3 ( 3.7 ) than on day 5 ( 2.2 ) . The number of blastocysts transferred did not affect the implantation rate , and pregnancy rates when either two or three blastocysts were transferred were 68 and 87 % respectively . The implantation rate of the blastocysts ( 50.5 % fetal heart beat ) was significantly higher compared to the cleavage stage embryos transferred on day 3 ( 30.1 % ) . The percentage of blastocyst development was not affected by the number of 2-pronuclear embryos , or by maternal age . Irrespective of the number of blastocysts formed , pregnancy rates were similar . Furthermore , the pregnancy rate following blastocyst transfer in patients with 10 or more follicles at the time of human chorionic gonadotrophin administration was not affected by patient age . More than 60 % of patients having blastocyst culture and transfer had supernumerary embryos for cryopreservation . The establishment of a pregnancy following thaw and transfer confirmed the viability of cryopreserved blastocysts cultured in the absence of serum or co-culture . The ability to transfer just two blastocysts while maintaining high pregnancy rates will therefore help to eliminate high order multiple gestations and improve the overall efficiency of human IVF Transfer of embryos at the blastocyst stage has been associated with exceptionally high implantation rates . There are , however , only a few prospect i ve r and omized studies comparing day 3 versus day 5 embryo transfer . Furthermore , the number of embryos replaced in the day 3 group transfer is often higher than the number of blastocysts replaced , thereby affecting implantation rates . A total of 118 patients undergoing st and ard IVF/intracytoplasmic sperm injection who had developed at least three 8-cell embryos showing < 20 % extracellular fragmentation on day 3 were r and omized for day 3 or day 5 transfer . A maximum of two embryos were replaced . In this prospect i ve , r and omized study the implantation and pregnancy potential of embryos transferred on day 3 or day 5 were compared . Equal numbers of embryos were replaced in the two groups . There was no statistically significant difference between day 3 and day 5 transfer regarding positive human chorionic gonadotrophin rates ( 70 versus 67 % ) , clinical pregnancy rates ( 61 versus 51 % ) , implantation rates ( 44 versus 37 % ) , twinning rates ( 42 versus 41 % ) and rates of early pregnancy loss ( 15 versus 29 % ) . Transfer of embryos on day 3 or 5 showed similar implantation rates when equal numbers of embryos were transferred . Embryo transfer at the blastocyst stage seems to have no advantage over day 3 transfer in patients with more than two 8-cell embryos showing less than 20 % fragmentation on day 3 BACKGROUND Whether extended culture allowing selection of embryos with high development potential has any advantage over cleavage-stage embryo transfer remains a matter of debate . Among the currently unsolved questions , the cumulative delivery rate result ing from fresh and frozen embryo transfers needs to be taken into account in both strategies . The aim of our study was , therefore , to compare the efficacy of single embryo transfer either on Day 2 or on Day 5/6 combining fresh and frozen embryo transfers . METHODS A prospect i ve study including 478 couples assigned on a voluntary basis to undergo elective single embryo transfer ( eSET , n = 243 ) on Day 2 or single blastocyst transfer ( SBT , n = 235 ) on Day 5/6 was performed . The primary outcome measurement was the cumulative delivery rate including fresh and frozen-thawed cycles in both groups . RESULTS The delivery rate per cycle following fresh embryo transfer was significantly higher in the SBT group compared with the eSET group ( P < 0.01 ) . Conversely , frozen embryo and /or blastocyst transfers tended to result in a higher number of deliveries in the eSET compared with the SBT group . Altogether , the cumulative delivery rate per couple , including fresh and frozen embryo transfers , was similar between the two groups ( 37.9 % versus 34.2 % in the SBT and eSET groups , respectively ) . CONCLUSIONS The observed cumulative delivery rates in this study do not allow us to take a position in favor of SBT or eSET . An improvement in blastocyst cryopreservation may change this attitude BACKGROUND This r and omized controlled study was performed in an unselected IVF/ICSI population to test the hypothesis that blastocyst transfers result in higher clinical pregnancy rates ( CPR ) per oocyte retrieval when compared with day 2 transfers . METHODS Blind r and omization for transfer on day 2 ( group 1 ) or day 5/6 ( group 2 ) was performed before stimulation . Oocytes and embryos were cultured in sequential media in 5.5 % CO(2 ) , 5 % O(2 ) , 89.5 % N(2 ) and 90 % humidity . A maximum of two embryos was transferred . RESULTS The two groups were similar for age , IVF indication  , number of treatment cycles , rate of ICSI/IVF , number of fertilized oocytes and number of embryos transferred . The CPR/oocyte retrieval was comparable in group 1 ( 32 % ) and in group 2 ( 44 % ) , while the CPR/embryo transfer was significantly higher ( P < 0.01 ) in group 2 ( 60 % ) than in group 1 ( 35 % ) . Similarly , the implantation rate per embryo transferred was significantly higher ( P < 0.03 ) in group 2 ( 46 % ) than in group 1 ( 29 % ) . The cryo-augmented delivery rate/oocyte retrieval was comparable in group 2 ( 36.3 % ) and in group 1 ( 28.6 % ) . CONCLUSION This r and omized study in an unselected population showed a significantly higher CPR/embryo transfer and a tendency toward a higher CPR/oocyte retrieval in patients receiving blastocysts when compared with day 2 transfers BACKGROUND The existence of a real benefit of blastocyst transfer is still a matter of debate . The 
    Output:
    
Current evidence shows no superiority of blastocyst compared with cleavage-stage embryo transfer in clinical practice .