***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: PURPOSE To compare outcome following in vitro fertilization-embryo transfer ( IVF-ET ) using controlled ovarian hyperstimulation ( COH ) regimens using either the gonadotropin-releasing hormone ( GnRH ) agonist leuprolide acetate vs the GnRH antagonist ganirelix . METHODS Women needing IVF for conception were r and omly assigned to 300 IU of gonadotropins with ganirelix used in the follicular phase when a follicle with a 14 mm average diameter was attained vs a regimen using leuprolide acetate from the mid-luteal phase of the previous cycle . RESULTS There were no differences found in clinical , ongoing , delivered pregnancy rates or implantation rates between groups . CONCLUSIONS The use of GnRH antagonists do not seem to reduce IVF outcome compared to using GnRH agonists in COH regimens OBJECTIVE To compare the efficacy of the long GnRH agonist and the fixed GnRH antagonist protocol s in IVF poor responders . STUDY DESIGN This was a r and omized controlled trial performed in the Iakentro IVF centre , Thessaloniki , from January 2007 to December 2011 , concerning women characterised as poor responders after having 0 - 4 oocytes retrieved at a previous IVF cycle . They were assigned at r and om , using sealed envelopes , to either a long GnRH agonist protocol ( group I ) or a GnRH antagonist protocol ( group II ) . RESULTS Overall 364 women fulfilled the inclusion criteria and were allocated to the two groups : finally 330 participated in our trial . Of these , 162 were treated with the  long GnRH agonist protocol  ( group I ) , and 168 with the fixed GnRH antagonist protocol  ( group II ) . Numbers of embryos transferred and implantation rates were similar between the two groups ( P = NS ) . The overall cancellation rate was higher in the antagonist group compared to the agonist group , but the difference was not significant ( 22.15 % vs. 15.2 % , P = NS ) . Although clinical pregnancy rates per transfer cycle were not different between the two groups ( 42.3 % vs. 33.1 % , P = NS ) , the clinical pregnancy rate per cycle initiated was significantly higher in the agonist compared to the antagonist group ( 35.8 % vs. 25.6 % , P=0.03 ) . CONCLUSIONS Although long GnRH agonist and fixed GnRH antagonist protocol s seem to have comparable pregnancy rates per transfer in poor responders undergoing IVF , the higher cancellation rate observed in the antagonist group suggests the long GnRH agonist protocol as the first choice for ovarian stimulation in these patients Objective To study if luteal E2 pre-treatment before GnRH antagonist protocol improves IVF/ICSI outcomes compared with st and ard long GnRH agonist protocol . Design A prospect i ve , r and omized and controlled study . Setting ART center of a state public hospitalPatient(s)Two hundred twenty infertile women underwent IVF/ICSI treatments . Intervention(s ) Participants received oral Estradiol Valerate 4 mg/day preceding the IVF cycle from day 21 until day 2 of next cycle before GnRH antagonist protocol ( E2 pre-treatment group n = 109 ) or received st and ard long GnRH agonist protocol as control group ( n = 111).Main outcome measure(s)Number of oocytes collected , MII oocytes , fertilization , implantation , live birth and early pregnancy rate , and hormone profiles . Result (s)E2 pre-treatment exerted a significant suppressive effect on FSH but not LH secretion compared with basal FSH and LH levels . In E2 pre-treatment group serum LH level was significantly higher during COH and serum P was also significantly higher on the day of HCG injection compared with control group . Five patients from E2 pre-treatment group had elevated LH at all time ( ≥10 IU/L ) and also a concomitantly high P ( > 1 ng/mL ) . Two of the five women achieved pregnancy but had early pregnancy loss . Overall , IVF/ICSI outcomes such as implantation , clinical pregnancy and live birth rates were similar between E2 pre-treatment and control groups . Conclusion (s)Luteal E2 pre-treatment before GnRH antagonist protocol significantly increases serum LH level and incidence rate of premature LH but no significant effect is observed on implantation , clinical pregnancy , live birth and early pregnancy loss rates compared with long GnRH agonist protocol . However , more studies in large numbers of cycles are needed to confirm that increased serum LH level by E2 pre-treatment during COH has no negative effect on the IVF/ICSI outcomes OBJECTIVE To evaluate whether the incidence of luteinizing hormone ( LH ) rise is reduced by using a flexible compared with a fixed day-6 protocol of GnRH antagonist administration . DESIGN R and omized controlled trial . SETTING Tertiary university hospital . PATIENT(S ) Patients undergoing in vitro fertilization ( n = 146 ) . INTERVENTION(S ) Ovarian stimulation was performed using recombinant FSH and GnRH antagonists . GnRH antagonist cetrorelix ( 0.25 mg/d ) was started either on day 6 of stimulation ( fixed group ) or when LH was > 10 IU/L , and /or a follicle with mean diameter > 12 mm was present , and /or serum E(2 ) was > 150 pg/mL. Patient monitoring was initiated on day 3 of stimulation . MAIN OUTCOME MEASURE(S ) Incidence of LH rise . RESULT ( S ) No statistically significant difference was observed between the flexible and fixed groups regarding the incidence of LH rise , which was lower in the flexible group ( 11.0 % vs. 15.1 % , difference -4.1 % , 95 % confidence interval -15.4 % to + 7.1 % ) . No LH surges were observed in any of the patients studied . CONCLUSION ( S ) Flexible antagonist administration from day 3 onward does not appear to reduce the incidence of LH rises compared with fixed antagonist administration on day 6 of stimulation Purpose To evaluate the results of gonadotropin-releasing hormone agonist ( GnRHa ) and gonadotropin-releasing hormone antagonist ( GnRHant ) use in two demographically matched groups of normoresponder in-vitro fertilisation or intracytoplasmic sperm injection ( IVF/ICSI ) patients in a prospect i ve study . Methods We r and omised 93 patients undergoing IVF/ICSI between May 2005 and August 2006 . Patients with IVF indications were included except for those with polycystic ovary syndrome or azoospermia , women older than 38 years and those with follicle-stimulating hormone ( FSH ) ≥10 IU/ml . Patients were stimulated with st and ard 225 IU recombinant FSH . In Group I ( n=45 ) a daily dose of GnRHant cetrorelix acetate 0.25 mg was administered when follicles reached a diameter of ≥14 mm . Group II ( n=48 ) patients were desensitised with the GnRHa , leuprolide acetate , in a long protocol . Human chorionic gonadotropin ( hCG ) was administered when at least three follicles of 18 mm in diameter were observed . Oocyte retrieval was scheduled 36 hours following hCG administration and embryos were transferred on day 3 after oocyte retrieval . Results The two groups were homogenous for age , infertility duration , basal FSH and serum oestradiol ( E2 ) ( P=0.537 , P=0.911 , P=0.103 and P=0.733 , respectively ) . In Group II ( the GnRHa group ) more antral follicles ( P<0.001 ) , a longer induction duration ( P=0.017 ) and higher peak E2 levels ( P<0.001 ) were observed . No differences were observed in the number of oocytes retrieved ( P=0.749 ) , embryos achieved and transferred ( P=0.677 ) , or fertilisation rates ( P=0.839 ) between the two groups . There was no statistically significant difference between groups in clinical pregnancy rates , cycle cancellation and ovarian hyperstimulation ( P=0.437 , P=0.109 and P=0.415 , respectively ) . Conclusion GnRHant and GnRHa provide comparable results in normoresponder patients , while GnRHant allows a greater flexibility in their treatment BACKGROUND The specific role of LH in folliculogenesis and oocyte maturation is unclear . GnRH antagonists , when administered in the late follicular phase , induce a sharp decrease in serum LH which may be detrimental for IVF outcome . This study was performed to evaluate whether the replacement of GnRH agonist ( triptorelin ) by a GnRH antagonist ( ganirelix ; NV Organon ) in oocyte donation cycles has any impact on pregnancy and implantation rates . METHODS A total of 148 donor IVF cycles was r and omly assigned to use either a GnRH antagonist daily administered from the 8th day of stimulation ( group I ) or a GnRH agonist long protocol ( group II ) for the ovarian stimulation of their donors . The primary endpoints were the pregnancy and the implantation rates . RESULTS The clinical pregnancy rate per transfer ( 39.72 % , 29/73 versus 41.33 % , 31/75 ) based on transvaginal scan findings at 7 weeks of gestation , the implantation rate ( 23.9 versus 25.4 % ) and the first trimester abortion rate ( 10.34 versus 12.90 % ) were similar in the two groups . CONCLUSION In oocyte donation cycles the replacement of GnRH agonist by a GnRH antagonist appears to have no impact on the pregnancy and implantation rates when its administration starts on day 8 of stimulation Objective To evaluate the effectiveness of GnRH antagonist multiple dose protocol applied during early and late follicular phase ( MDP-EL ) in comparison with st and ard GnRH agonist luteal long protocol ( LP ) in each non-obese and obese polycystic ovary syndrome ( PCOS ) women undergoing IVF . Methods Two hundred eleven infertile women with PCOS were recruited and r and omized to undergo either GnRH antagonist MDP-EL ( antagonist group ) or st and ard GnRH agonist luteal LP ( agonist group ) . IVF cycle outcomes were compared between the two groups . Results Total dose and days of recombinant human follicle stimulating hormone ( rhFSH ) administered were significantly fewer in the antagonist group than in the agonist group . Incidence of severe ovarian hyperstimulation syndrome was significantly lower in the antagonist group . However , IVF and pregnancy outcomes were similar in the two groups . When all subjects were divided into non-obese and obese subgroups , in non-obese PCOS subgroup , IVF and pregnancy outcomes were comparable in the antagonist and agonist groups but total dose and days of rhFSH were also significantly fewer in the antagonist group . Similar findings were also observed in obese PCOS subgroup . Conclusion GnRH antagonist MDP-EL is at least as effective as GnRH agonist LP and may be a more patient-friendly alternative in controlled ovarian stimulation for PCOS patients undergoing IVF , independent of body mass index OBJECTIVE To compare the effects of oral contraceptive ( OC ) pill pretreatment in recombinant FSH/GnRH-antagonist versus recombinant FSH/GnRH-agonist stimulation in in vitro fertilization ( IVF ) patients , and to evaluate optimization of retrieval day . DESIGN Prospect i ve , r and omized , multicenter study . SETTING Private practice and university centers . PATIENT(S ) Eighty patients undergoing IVF who met the appropriate inclusion criteria . INTERVENTION(S ) Four study centers recruited 80 patients . The OC regimen began on cycle days 2 to 4 and was discontinued on a Sunday after 14 to 28 days . The recombinant FSH regimen was begun on the following Friday . The GnRH-agonist group was treated with a long protocol ; the GnRH-antagonist was initiated when the lead follicle reached 12 to 14 mm . When two follicles had reached 16 to 18 mm , hCG was administered . MAIN OUTCOME MEASURE(S ) The primary outcome measures were the number of cumulus-oocyte complexes , day of the week for oocyte retrieval , and total dose and days of stimulation of recombinant FSH .  Secondary efficacy variables included pregnancy and implantation rate ; serum E(2 ) levels on stimulation day 1 ; serum E(2 ) , P , and LH levels on the day of hCG administration ; follicle size on day 6 and day of hCG administration ; the total days of GnRH-analogue treatment ; total days on OC ; total days from end of OC to oocyte retrieval ; and the cycle cancellation rate . RESULT ( S ) Patient outcomes were similar for the days of stimulation , total dose of gonadotropin used , two-pr 
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WIDER IMPLICATION S In a general IVF population , GnRH antagonists are associated with lower ongoing pregnancy rates when compared to long protocol agonists , but also with lower OHSS rates .
Thus st and ard use of the long GnRH agonist treatment is perhaps still the approach of choice for prevention of premature luteinization .
In couples with PCOS and poor responders , GnRH antagonists do not seem to compromise ongoing pregnancy rates and are associated with less OHSS and therefore could be considered as st and ard treatment