***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 
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    ***EXAMPLES*** 
    Input: BACKGROUND It is generally accepted that the age-related increased aneuploidy rate is correlated with reduced implantation and a higher abortion rate . Therefore , advanced maternal age ( AMA ) couples are a good target group to assess the possible benefit of preimplantation genetic diagnosis for aneuploidy screening ( PGD-AS ) on the outcome after assisted reproductive technology ( ART ) . METHODS A prospect i ve r and omized controlled clinical trial ( RCT ) was carried out comparing the outcome after blastocyst transfer combined with PGD-AS using fluorescence in situ hybridization ( FISH ) for the chromosomes X , Y , 13 , 16 , 18 , 21 and 22 in AMA couples ( aged > or = 37 years ) with a control group without PGD-AS .  From the 400 ( 200 for PGD-AS and 200 controls ) couples that were allocated to the trial , an oocyte pick-up was performed effectively in 289 cycles ( 148 PGD-AS cycles and 141 control cycles ) . RESULTS Positive serum HCG rates per transfer and per cycle were the same for PGD-AS and controls : 35.8 % ( 19.6 % ) [ % /per embryo transfer ( per cycle ) ] and 32.2 % ( 27.7 % ) , respectively ( NS ) . Significantly fewer embryos were transferred in the PGD-AS group than in the control group ( P<0.001 ) . The implantation rate ( with fetal heart beat ) was 17.1 % in the PGD-AS group versus 11.5 % in the control group ( not significant ; P=0.09 ) . We observed a normal diploid status in 36.8 % of the embryos . CONCLUSIONS This RCT provides no arguments in favour of PGD-AS for improving clinical outcome per initiated cycle in patients with AMA when there are no restrictions in the number of embryos to be transferred 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 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 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 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 aim of this study was to compare , in a prospect i ve r and omized trial , the outcome of day 2 and day 5 transfer of human embryos cultured in an ' in-house ' sequential medium . METHODS A total of 193 cycles from 171 patients with less than four previous IVF cycles , < 39 years old and with four or more zygotes on day 1 , were r and omly allocated to day 2 ( 94 cycles ) or day 5 ( 99 cycles ) transfer . Zygotes were kept in fertilization medium until 18 h post-fertilization and then placed in a ' glucose-free ' cleavage medium . Embryos allocated for day 5 transfer were placed in a blastocyst medium 66 h post-fertilization . Two or three embryos were replaced according to the morphology . RESULTS A mean ( + /- SEM ) number of 2.1 + /- 0.4 and 1.9 + /- 0.3 embryos were replaced on day 2 and day 5 ( P < 0.001 ) respectively . Delivery rates per transfer were 44.1 and 37.1 % [ P = not significant ( NS ) ] , implantation rates were 31.4 and 29.4 % ( NS ) and multiple delivery rates 22 and 36 % ( NS ) for day 2 and day 5 groups respectively . Ten patients ( 10.1 % ) had no blastocysts available for transfer . CONCLUSIONS No clear benefits were observed using blastocyst transfer for patients aged < 39 years who had had less than four previous IVF cycle attempts OBJECTIVES To compare the implantation rate of embryos after 3 and 5 days of IVF culture . DESIGN Prospect i ve r and omization of ET depending on the weekday of ovum pick-up ( OPU ) . SETTING University Department of Endocrinology and Reproduction . PATIENTS All women entering an outclinic IVF program . INTERVENTIONS Two hundred thirty-three ETs performed on day 3 after OPU and 410 performed on day 5 were analyzed . When blastocysts with a clear inner cell mass were available , a maximum of two were replaced . RESULTS On day 3 after OPU , 60 pregnancies per 233 ET ( 26 % ) and on day 5 , 102 pregnancies per 410 ET ( 25 % ) were induced . The average implantation rate per embryo was 13 % and 12 % , respectively . After subdivision according to embryo morphology , pregnancy rate per ET ( n = 59 ) and implantation rate per embryo on day 3 with exclusively unfragmented embryos were 32 % and 18 % , respectively , not significantly different from ET ( n = 73 ) exclusively with embryos containing > 0 % and < 20 % fragments : 27 % and 12 % . After transfer on day 5 , when one or more cavitating embryos were available ( n =  
    Output:
    
The best available evidence suggests that the probability of live birth after fresh IVF is significantly higher after blastocyst-stage embryo transfer as compared to cleavage-stage embryo transfer when equal number of embryos are transferred in the two groups compared