***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 Cryopreservation of embryos may lead to zona hardening that may compromise in vivo hatching and implantation following thawing and transfer . Assisted hatching ( AH ) has been advocated as a means of assisting the natural hatching process and enhancing implantation . METHODS The aim of this study was to assess in a prospect i ve r and omized manner the effect of laser-assisted hatching ( LAH ) on implantation as well as clinical and multiple pregnancy rates ( the primary outcome ) after the transfer of frozen-thawed embryos . All embryos were thawed the day before transfer , and LAH was performed the next day on embryos that cleaved . Control group consisted of embryos that were transferred without AH . RESULTS The performance of LAH significantly increased implantation ( 9.9 versus 20.1 % , P < 0.01 ) , clinical pregnancy ( 27.3 versus 40.9 , P < 0.05 ) and multiple pregnancy rates ( 16 versus 40.3 % , P < 0.07 ) . In the LAH group , significantly more excess embryos that were left in culture hatched in vitro . CONCLUSIONS LAH improves the outcome of frozen-thawed embryo transfer when performed before transfer on embryos that were allowed to cleave Background : Routine use of assisted hatching ( AH ) following ICSI is a controversial issue in the literature . There are rare studies regarding the effect of laser assisted hatching ( LAH ) on live birth rate . Objective : Our main goal was to evaluate the effect of LAH on delivery rate as well as congenital anomaly in patients undergoing their first ICSI cycle . Material s and Methods : A total of 182 patients subjected to ICSI  were r and omly aliquot into two groups of experiment and control . In experiment group , the embryos were subjected to LAH to open a hole in ZP ( about 10 - 12 µm ) while in control group , the transferred embryos were intact with no AH . The patients were followed for clinical pregnancy and delivery rate as well as congenital anomaly .  All the patients were infertile due to male factor infertility and LAH and embryo transfer were done on day 2 . Results : Laboratory and clinical characteristics of two groups of experiment and control were the same . There were insignificant differences between two groups of experiment and control for clinical pregnancy rate ( 20 % vs. 23.9 % , respectively , p=0.3 ) and live birth rate ( 11.11 % vs. 8.6 % , respectively , p=0.6 ) . Also no significant differences were observed between two groups of experiment and control for multiple pregnancy as well as congenital anomaly . Conclusion : Routine use of LAH in first ICSI cycle for male factor patients may have no beneficial effects on clinical pregnancy and live birth rate 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 Flaws in the design , conduct , analysis , and reporting of r and omised trials can cause the effect of an intervention to be underestimated or overestimated . The Cochrane Collaboration ’s tool for assessing risk of bias aims to make the process clearer and more 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 BACKGROUND Assisted hatching ( AH ) in fresh embryo transfer ( ET ) cycles increases the implantation and pregnancy rates , especially in women with a poor prognosis , repeated implantation failures and in older women . Little information exists in the literature regarding the role of AH in frozen-thawed embryo transfer ( FET ) cycles . METHODS Embryos were cryopreserved at the cleavage stage . On the day of FET , 160 patients were r and omized according to a computer-generated r and omization list in sealed envelopes into the  AH group and the  control group . The patients and the clinicians were blinded to the group assigned . In the AH group , the outer half of the zona pellucida over a quarter of the diameter of zona was removed using a 1480 nm non-contact laser . RESULTS The two groups were comparable in terms of demographic characteristics , ovarian response of the stimulated cycle and quality of fresh and frozen-thawed embryos . No differences in implantation , pregnancy and multiple pregnancy rates were found between the two groups . There was a non-significant trend of a higher implantation rate in the AH group when the zona thickness was > or = 16 mm . CONCLUSION Laser AH did not improve the implantation rate of FET cycles and should not be performed routinely in all frozen-thawed embryos at the cleavage stage Abstract Purpose : The objective of this study was to determine if the zona thinning ( ZT ) technique improved the rates of implantation and clinical pregnancy for patients aged ≥38 years su bmi tted to an ICSI program . Methods : A total of 100 patients su bmi tted to ICSI and aged ≥38 years were divided in a prospect i ve and r and omized manner into two groups : Group I – patients su bmi tted to ZT ( n = 50 ) ; a laser diode with 1.48 μm wavelength ( Fertilaser ) was used for the ZT procedure with 1–2 irradiations of 10 ms applied to four different positions on the zona pellucida ( ZP ) of each embryo to thin 60–90 % of the ZP ( each point with a 15–20 μm length of ZT ) . Group II – patients with no ZT ( n = 50 ) . In both groups , embryo transfer was performed on the second or third day . Results : The age of Group I patients ( 39.8 ± 1.3 ) did not differ ( p = 0.67 ) from that of Group II patients ( 40 ± 1.9 ) . The number of oocytes retrieved at metaphase II from Group I ( 6.4 ± 4.2 ) and Group II ( 6.8 ± 5 ) was similar ( p = 0.94 ) . Normal fertilization rates and cleavage rates were similar ( p = 0.78 and p = 0.63 , respectively ) for Group I ( 71.5 ± 22 % and 96.7 ± 11 % ) and Group II ( 73.5 ± 19.7 % and 96 ± 11 % , respectively ) . The number of embryos transferred was similar ( p = 0.53 ) for the two groups ( Group I = 3.1 ± 1.3 ; Group II = 2.9 ± 1.1 ) . The thickness of the ZP of Group I embryos ( 16.9 ± 2.4 μm ) did not differ ( p = 0.97 ) from that of Group II embryos ( 16.9 ± 2.3 μm ) . The rates of embryo implantation and clinical pregnancy per embryo transfer were similar ( p = 0.67 , p = 0.61 ) for Group I ( 7 and 16 % , respectively ) and for Group II ( 8.2 and 22 % , respectively ) . Conclusions : These results suggest that ZT in the population aged ≥38 years may have no impact on ICSI success rates . However , this conclusion is limited to a situation in which length of the laser ZT was ≤20 μm and the laser was applied to four different positions Implantation failure after IVF is one of the factors associated with a reduced chance of pregnancy for some patients .  Assisted hatching method ologies are design ed to facilitate the embryo 's escape from the zona pellucida , and this strategy has been suggested as a means of improving pregnancy rates in patients with previous implantation failure . The aim of this prospect i ve and r and omized study was to evaluate the efficacy of quarter-laser zona thinning assisted hatching ( qLZT-AH ) in improving the implantation of embryos in patients with previous implantation failure . A total of 150 patients with a history of previous impl 
    Output:
    
In summary , this meta- analysis supports that AH was associated with an increased chance of achieving clinical pregnancy and multiple pregnancy .