***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: Aim : To evaluate the effect of local injury to the endometrium during spontaneous menstrual cycles before in vitro fertilization ( IVF ) treatment on implantation and pregnancy rates in women with recurrent implantation failure ( RIF ) . Methods : In a prospect i ve r and omized controlled trial ( RCT ) , a total of 36 patients , with RIF undergoing IVF  , were r and omized to two groups . In 18 patients , endometrial biopsies were performed using a pipelle curette on days 9–12 and 21–24 of the menstrual cycle preceding IVF treatment . In 18 control patients , a cervical pipelle was performed . Results : The implantation rate ( 2.08 % versus 11.11 % ; p = 0.1 ) , clinical ( 0 % versus 31.25 % ; p < 0.05 ) and live births rates ( 0 % versus 25 % ; p = 0.1 ) were lower in the experimental group compared with controls . Conclusion : Our RCT did not find any benefit from local injury to the endometrium in women with a high number of RIFs . Further studies are warranted to better define the target population of patients who may benefit from this procedure OBJECTIVES To investigate the effect of endometrial scratching , performed during oral contraceptive pill ( OCP ) pretreatment , on reproductive outcome and on ultrasound markers of endometrial receptivity , and to assess the pain involved in the procedure , in unselected women undergoing assisted reproductive techniques ( ART ) . METHODS Women undergoing ART were r and omly allocated to undergo either endometrial scratching with a pipelle de Cornier or a sham procedure , 7 - 14 days before starting controlled ovarian stimulation ( COS ) . We evaluated subsequent rates of clinical pregnancy , live birth , implantation , miscarriage and multiple pregnancy . Pain during the procedure was evaluated using a 10-cm visual analog scale . Endometrial thickness and volume and three-dimensional power Doppler ( 3D-PD ) indices ( vascularization index ( VI ) , flow index ( FI ) and vascularization flow index ( VFI ) ) were assessed during COS when there was at least one follicle ≥ 17 mm in diameter . RESULTS We included 158 women . Endometrial scratching was associated with higher rates of live birth ( 41.8 % vs 22.8 % , P = 0.01 ) and clinical pregnancy ( 49.4 % vs 29.1 % , P = 0.01 ) and higher pain score ( 6.42 ± 2.35 cm vs 1.82 ± 1.52 cm , P < 0.001 ) , endometrial VI ( 3.71 ± 1.77 vs 2.95 ± 1.56 , P < 0.01 ) and VFI ( 0.97 ± 0.51 vs 0.76 ± 0.40 , P < 0.01 ) . There was no significant effect of endometrial scratching on rate of miscarriage ( 15.4 % vs 21.7 % , P = 0.53 ) or multiple pregnancy ( 22.5 % vs 25.0 % , P = 0.79 ) , or on endometrial thickness ( 10.12 ± 1.55 mm vs 9.98 ± 1.62 mm , P = 0.59 ) , endometrial volume ( 6.18 ± 1.63 cm(3 ) vs 6.01 ± 1.48 cm(3 ) , P = 0.51 ) or FI ( 26.12 ± 2.82 vs 25.91 ± 2.72 , P = 0.65 ) . CONCLUSIONS Endometrial scratching performed once , during OCP pretreatment 7 - 14 days before starting COS , increases the chance of live birth and clinical pregnancy , but might cause considerable pain OBJECTIVE To evaluate the effect of a single endometrial biopsy regimen ( S-EBR ) in the cycle preceding the ICSI cycle in patients with repeated implantation failure . STUDY DESIGN This was a prospect i ve r and omized controlled trial which included two-hundred infertile women with a history of repeated implantation failure . The subjects were r and omly divided into two groups . Group A subjects underwent hysteroscopy and endometrial scraping by Novak curette in the cycle preceding the ICSI cycle , while group B subjects underwent hysteroscopy without endometrial scraping .  Implantation rate , clinical pregnancy rate , abortion rate and live birth rate were compared between both groups . RESULTS The number of retrieved oocytes in group A was 11.6 ± 3 and in group B was 11.6 ± 2.8 with no statistically significant difference ( p=0.787 ) . There were statistically significant differences regarding the implantation rate , the clinical pregnancy rate and live birth rate . The implantation rate in group A was 12 % while in group B it was 7 % ( p=0.015 ) , the clinical pregnancy rate was 32 % in group A while it was only 18 % in group B ( p=0.034 ) and the live birth rate was 28 % in group A while it was 14 % in group B ( p=0.024 ) . CONCLUSIONS The single endometrial biopsy regimen ( S-EBR ) performed during hysteroscopy has statistically significant higher implantation rate , clinical pregnancy rate and live birth rate than hysteroscopy without endometrial scraping 
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But , as the critics rightfully point out , studies that include meta-analyses are often not without biases .