***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: The objective of this study was to determine if assisted hatching improved the rates of implantation , clinical pregnancy and ongoing pregnancy for in-vitro fertilization ( IVF ) patients aged > or = 36 years . On the day of oocyte aspiration , consenting patients were r and omized according to whether all embryos underwent the hatching procedure ( hatched ; n = 41 ) or all embryos remained unhatched ( controls ; n = 48 ) . Patients in both groups were treated with methylprednisolone and doxycycline starting on the day of oocyte retrieval and continuing for 4 days . The hatching procedure was performed approximately 55 h after insemination on all potential embryos for transfer and employed the release of acidified acid Tyrode 's medium against the zona pellucida to create an opening approximately 20 microm in diameter . No significant differences were noted in the mean age , number of oocytes aspirated and number of embryos transferred between the hatched and control groups . In addition , no significant differences were observed in the rates of implantation ( 11.1 versus 11.3 % ) , clinical pregnancy ( 39.0 versus 41.7 % ) and ongoing pregnancy ( 29.3 versus 35.4 % ) between the hatched and control groups respectively . These results suggest that assisted hatching may have no significant impact on IVF success rates in the patient population studied Abstract Purpose : The role of assisted hatching in good-prognosis IVF patients was evaluated in a prospect i ve , r and omized , controlled pilot study , which was followed by a retrospective observational series . Methods : After assisted hatching was proved successful in a mouse embryo study , 20 good-prognosis IVF patients were r and omly assigned to either assisted hatching ( 13 ) or no assisted hatching ( 7 ; the controls ) . Following this series , 27 good-prognosis IVF patients were retrospectively evaluated to determine the outcome with assisted hatching . Results : In the prospect i ve study , clinical pregnancies result ed from 3 ( 23 % ) of 13 patients in the hatching group , compared to 3 ( 43 % ) of 7 in the control group . Implantation rates were similar : 9.6 % in the hatching group and 10.7 % in the controls . In the retrospective series , the 11.1 % implantation rate with assisted hatching was significantly less than the 42.9 % implantation rate seen with traditional IVF . Conclusions : Implantation and pregnancy rates are high in young women undergoing traditional IVF . Assisted hatching is not beneficial in these patients OBJECTIVE To assess the effect of augmenting IVF with assisted hatching in the treatment of patients with repeated IVF failures . DESIGN Prospect i ve r and omized study . SETTING Division of Reproductive Endocrinology and Infertility of National Taiwan University Hospital . PATIENT(S ) From July 1993 to February 1996 , 49 patients with repeatedly failed IVF were treated with assisted hatching and were compared with 51 control subjects without assisted hatching .  INTERVENTION(S ) Assisted hatching . MAIN OUTCOME MEASURE(S ) Pregnancy rate and implantation rate per embryo after IVF-ET or IVF-tubal ET ( TET ) were measured . RESULT ( S ) The pregnancy rate ( PR ) in the assisted hatching group was found to be 36.7 % compared with 19.6 % in the control group , but the difference was not significant . When only patients receiving IVF-ET were considered , it was observed that the PR was significantly higher in the assisted hatching group than the control group ( 42.4 % versus 16.1 % ) . With IVF-TET however , the PR was found to be similar in both assisted hatching and control groups ( 25.0 % and 25.0 % , respectively ) . The rate of embryonic implantation in the IVF-ET patients was 11.0 % , which was significantly higher than that of control embryos ( 3.7 % ) . CONCLUSION ( S ) These results implied that IVF-ET , combined with assisted hatching , may improve the PR and implantation rate in patients with repeated IVF failures , but the same was not true in the case of IVF-TET In two separate prospect ively r and omized trials , intracytoplasmic sperm injection ( ICSI ) cycles were studied in a controlled manner to monitor the effects of either bovine oviductal epithelial cell co-culture ( n = 119 ) or assisted hatching by zona drilling ( n = 100 ) . In the first study , immediately following ICSI , all eggs were placed directly either onto partial monolayers of bovine oviductal cells or into regular culture medium . Although the embryo developmental rate was apparently compromised in part by the presence of the co-culture cells , ultimately there were no significant differences in either the viable pregnancy rate ( 31.6 % co-culture versus 29.0 % control ) or the embryonic implantation rate ( 11.4 % co-culture versus 13.6 % control ) . Assisted hatching also had no significant impact on ICSI cycle outcome in terms of either the viable pregnancy rate ( 30.0 % assisted hatching versus 32.0 % control ) or the embryonic implantation rate ( 8.5 % assisted hatching versus 13.5 % control ) . However , in female patients aged > or = 35 years , assisted hatching appeared to convey a marginally significant benefit in terms of both the viable pregnancy rate ( 35.5 % assisted hatching versus 11.1 % control ) and the embryonic implantation rate ( 10.3 % assisted hatching versus 3.1 % control ) . It seems that the overall improvement of ICSI cycle outcome can not be achieved by the general application of either co-culture or assisted hatching . Nevertheless , it is possible that there remain specific patient groups that might benefit from selected use of either of these modalities OBJECTIVE The aims of this study were to compare preimplantation embryo quality in intracytoplasmic sperm injection ( ICSI ) with st and ard IVF  and to examine the impact of age and number and quality of embryos transferred on implantation and pregnancy . DESIGN Retrospective , controlled clinical study . SETTING Academic tertiary center . PATIENT(S ) We examined 211 consecutive couples undergoing ICSI who were matched with 211 couples undergoing IVF therapy during the same time frame . INTERVENTION(S ) In vitro embryo culture . MAIN OUTCOME MEASURE(S ) Day 3 embryo quality as judged by the number of blastomeres and morphology scoring . RESULT ( S ) Patients undergoing ICSI  had a significantly reduced number of embryos with good morphology and cleavage compared with IVF cases . Nevertheless , pregnancy and abortion rates were similar when adjusted by age and number of embryos transferred . Average cleavage status and age were significant predictors of implantation . Women of advanced age had significantly lower embryo cleavage and implantation rates . CONCLUSION ( S ) [ 1 ] The cleaving status of day 3 embryos is a valuable , although limited , indicator of implantation outcome . [ 2 ] In vitro fertilization-derived embryos had better cleavage rates and morphology scores than ICSI-derived embryos ; however , the implantation potential was similar for both groups . [ 3 ] The age-related decline in implantation rate was associated with impaired embryo growth rates Abstract Purpose : Preliminary data from some research centers indicate that assisted hatching might be of value to increase embryo implantation rate in the human , at least in selected cases . It is not clear , however , whether this technique would be of benefit for all patients undergoing an embryo transfer . We therefore performed a prospect i ve r and omized study to evaluate the effect of assisted hatching on the implantation rate in our in vitro fertilization (IVF)/intracytoplasmic sperm injection ( ICSI ) program . Methods : In total , 120 couples undergoing an embryo transfer were r and omized between two groups : in one group no assisted hatching was performed ( AH− ) , whereas in the other group the embryos selected for transfer were subjected to partial zona dissection ( PZD ) immediately prior to the transfer ( AH+ ) . Using a computer-generated minimization procedure , patients were allocated to one of the two groups according to four preselected criteria : the number of embryos transferred , the cumulative score of transferred embryos , the age of the patient , and the use of ICSI . Results : Pregnancy and implantation rates in the AH+ and AH− groups were , respectively , 42.1 versus 38.1 % and 17.9 versus 17.1 % . Conclusions : From our data we conclude that assisted hatching through partial zona dissection prior to embryo transfer does not improve pregnancy and embryo implantation rates in unselected patients undergoing IVF or ICSI From 1993 to 1994 , in our centre , laser-assisted hatching was performed on 2- to 4-cell stage embryos obtained from in-vitro fertilization ( IVF ) patients . We treated 376 embryos from 96 patients with repeated IVF failures ( two to four attempts ) ( group A ) and 397 embryos from 111 patients undergoing IVF for the first time ( group B ) . Embryos were transferred immediately after the laser treatment . Both groups were compared to control groups ( A ' and B ' ) whose embryos were transferred with intact zona pellucida ( ZP ) . The result ing clinical pregnancies were 41 in A and 44 in B versus 24 in A ' and 23 in B ' respectively . The pregnancy rates per patient were 42.7 and 39.6 % versus 23.1 and 19 % in the control groups ( P < or = 0.05 ) , while the implantation rates per embryo were 12.2 % in A and 11.8 % in B versus 7.3 % and 7.1 % . These results show that laser zona thinning of human embryos at 48 h after egg retrieval significantly increases the implantation and pregnancy rate ( P < or = 0.05 ) Assisted hatching by zona drilling using acidic Tyrode 's solution was performed during three r and omized trials in 330 in-vitro fertilization patients . The trials were design ed in order to study the overall effect of the procedure and whether characteristic patient [ i.e. maternal age and basal levels of follicle stimulating hormone ( FSH ) ] and embryonic features ( i.e. zona pellucida thickness ) are important for the decision to perform assisted hatching routinely . Couples ( n = 137 ; Trial 1 ) in whom the female partner had normal basal FSH levels were r and omized in a  control group ( without micromanipulation ) and a zona drilling group ( all embryos micromanipulated ) . The incidence of implantation ( 67/239 ; 28 % ) of zona-drilled embryos compared favourably with that of control embryos ( 49/229 ; 21 % ) , but the difference was not significant . Retrospective analysis revealed that those embryos whose zonae were thicker than 15 microns were rescued . In order to test the validity of this finding , selective assisted hatching was performed on embryos with a poor prognosis in 163 other patients ( Trial 2 ) . The couples were r and omized into a control group and a group in which embryos were selectively zona-drilled , based on zona thickness and other embryonic features . The rate of embryonic implantation in the selectively zona-drilled group was 25 % ( 70/278 ) , significantly ( P less than 0.05 ) higher than that of control embryos ( 51/285 ; 18 % ) . Although it was demonstrated retrospectively and prospect ively that assisted hatching by zona drilling is effective in embryos with thick zonae ( greater than or equal to 15 microns ) , patients whose embryos have thin ( less than 13 microns ) zonae may be jeopardized by the procedure . ( ABSTRACT TRUNCATED AT 250 WORDS Abstract Purpose : In this prospect i ve r and omized study the effectsof enzymatic treatment of zona pellucida of blastocysts onimplantation and pregnancy rates were evaluated in a groupof patients who had more than five embryos on day 3 . Methods : Forty-six patients with a mean age of 29.8 ± 4.5years and mean duration of infertility of 6.72 ± 0.63 yearshad blastocyst stage transfers , with a mean number of2.9 ± 0.1 embryos replaced per patient . Patients were r and omlydivided into two groups . The first group consisted of patients ( n = 22 ) who had zona intact blastocyst stagetransfers  and the second group consisted of patients ( n = 24)who had zona manipulated ( enzymatic treatment ) blastocyststage transfers . Patient and cycle characteristics were similarin both groups . A commercial cell and serum-free sequentialculture system was used for all embryos . Results : Overall blastocyst formation rate was 50.3%.Transfer could be done in all patients . The positive β-humanchorionic gonadotropin rate in the zona intact group was50 % ( 11/22 ) and in the zona-manipulated group was 70.8%(17/24 ) . Clinical pregnancy , ongoing pregnancy , and implantation rates in zona intact and manipulated groupswere 45.5 % , 27.3 % , and 19 % , and 6 
    Output:
    
Meta-regression suggested that AH might be more useful in older women .