***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 Controlled ovarian hyperstimulation has been shown to advance endometrial maturation and adversely affects implantation in ART . It has been reported that there is a better embryo-endometrium synchrony in frozen-thawed embryo transfer cycles than fresh embryo transfer cycles . The objective of this study was to compare ongoing pregnancy rates between fresh ET and FET cycles . Methods In an open prospect i ve , controlled study , the patients who were classified as high responders , were r and omized to either fresh ET or FET .  The embryos in FET group were cryopreserved with vitrification by Cryotop method . Results A total of 374 patients were included , 187 of which were r and omized to FET and 187 to fresh ET .  There were 39 % ( n = 73 ) ongoing pregnancy in FET group compared with 27.8 % ( n = 52 ) in fresh ET group[odds ratio = 1.66;95 % confidence interval = 1.07–2.56 ; p = 0.02 ] . Conclusions FETs can be performed instead of fresh ETs to improve the outcome of ART in highly selected patients To determine the relationship between serum progesterone on the day of human chorionic gonadotrophin ( HCG ) and the pregnancy outcome of  IVF-embryo transfer treatment , 251 infertile patients undergoing IVF-embryo transfer with gonadotrophin-releasing hormone agonist ( GnRHa ) and recombinant FSH ( rFSH ) were prospect ively studied . Among them , 118 patients underwent 118 cycles of frozen embryo transfer ( FET ) treatment  , one cycle per patient . All the cycles were grouped according to serum progesterone concentration on the day of HCG administration ( < 3.97 nmol/l or > /=3.97 nmol/l ) . The incidence of progesterone elevation was 36.7 % ( 92/251 ) , and in this group the pregnancy rate was significantly lower ( 25.97 versus 48.57 % ; P < 0.001 ) . If the serum progesterone on the day of HCG was over 6.0 nmol/l , their pregnancy outcome was much poorer ( 13.79 versus 44.68 % ) . However , the pregnancy rate was similar in FET cycles whether the serum progesterone was over 3.97 nmol/l ( 34.00 versus 36.76 % ) or 6.0 nmol/l ( 42.86 versus 34.02 % ) . In conclusion , serum progesterone on the day of HCG may predict IVF pregnancy outcome . The higher serum oestradiol and progesterone concentrations may affect endometrial receptivity . For patients with an extremely high progesterone concentration on the day of HCG ( such as over 6.0 nmol/l ) , transfer of frozen embryos in a natural cycle is suggested OBJECTIVE To determine if an increase in plasma P occurring before hCG administration might impair the outcome of  IVF-ET . DESIGN Five hundred eighty-five IVF-ET cycles were prospect ively studied for the occurrence of plasma P elevation before hCG administration . SETTING Tertiary institution , IVF-ET program , Hôpital A. Béclère . PATIENTS Participating patients included IVF-ET c and i date s 23 to 42 years of age only , excluding the couples in whom a male factor was a primary or an accessory cause of infertility . MAIN OUTCOME MEASURES To clarify the practical consequences on IVF-ET outcome of pre-hCG increases in plasma P , we studied 585 consecutive IVF-ET cycles . These were divided into two groups according to plasma P levels observed on the day of hCG administration ; plasma P of 0.9 ng/mL ( 2.9 nmol/L ) was taken as an arbitrary cutoff value . Group A included 485 IVF cycles in which plasma P was < or = 0.9 ng/mL ( 2.9 nmol/L ) ; group B included the remaining 100 cycles in which plasma P was > 0.9 ng/mL ( 2.9 nmol/L ) . RESULTS The number of mature oocytes retrieved , the oocyte cleavage rate , and the number of embryos obtained were similar in groups A and B. In contrast to this apparent similarity in oocyte quality , a decrease in pregnancy rate ( PR ) and a trend for a decrease in embryo implantation rate were observed in group B in comparison with group A. CONCLUSIONS The similar fertilization and cleavage rates obtained in groups A and B suggest that pre-hCG elevation in plasma P does not lead to decreased oocyte quality . Yet the lower PR observed when plasma P rises prematurely suggests that the prolonged but discrete elevation in plasma P occurring in these cases might alter endometrium receptivity to embryo implantation BACKGROUND In view of the current debate concerning possible differences in efficacy between the two GnRH analogues used in IVF stimulated cycles , the current study aim ed to explore whether progesterone control in the late follicular phase differs when GnRH antagonist is used as compared with GnRH agonist , and if so , to what extent the progesterone rise affects the probability of pregnancy . METHODS Overall 190 patients were r and omized : 94 in the GnRH-agonist group and 96 in the GnRH-antagonist group . The GnRH-agonist long protocol started on Day 21 of the preceding cycle with intranasal buserelin ( 600 mg per day ) . The GnRH-antagonist protocol started on Day 6 of the stimulation with ganirelix or cetrorelix ( each 0.25 mg ) . All blood sample s were analysed with the Elecsys analyzer . An intention-to-treat analysis was applied . RESULTS A progesterone rise > 1.5 ng/ml was noticed in 23.0 % of the antagonist group , comparable with 24.1 % incidence within the agonist group . Per patient r and omized , delivery rates were also comparable : 28.1 % in the antagonist group and 24.5 % in the agonist group ( odds ratio = 1.21 , 95 % confidence interval : 0.63 - 2.31 , P= 0.56 ) . However , there was a reduction in delivery rates when progesterone exceeded the threshold of 1.5 ng/ml , both in the agonist group ( 9.5 versus 31.8 % , P= 0.03 ) and in the antagonist group ( 14.3 versus 34.3 % , P= 0.07 ) . CONCLUSIONS Although the incidence of a progesterone rise was similar between the two analogues , our findings reconfirm previous observations that insufficient progesterone control ( > 1.5 ng/ml ) on the day of ovulation triggering is related to poor delivery rates in both protocol s. The current study has shown that the reproductive outcomes with the two GnRH analogues are comparable . Possible modes of action to circumvent late follicular progesterone rise should be explored . TRIAL REGISTRATION NUMBER NCT01191710 BACKGROUND LH activity may influence treatment response and outcome in IVF cycles . METHODS A r and omized , assessor-blind , multinational trial compared ongoing pregnancy rates ( primary end-point ) in 731 women undergoing IVF after stimulation with highly purified menotrophin ( HP-hMG ) ( n = 363 ) or recombinant FSH ( rFSH ) ( n = 368 ) following a long GnRH agonist protocol .  Patients received identical pre- and post-r and omization interventions . One or two embryos were transferred on day 3 . RESULTS More oocytes were retrieved ( P < 0.001 ) after rFSH treatment ( 11.8 ) compared with HP-hMG treatment ( 10.0 ) , but a higher proportion developed into top- quality embryos ( P = 0.044 ) with HP-hMG ( 11.3 % ) than with rFSH ( 9.0 % ) . At the end of stimulation , lower estradiol ( E(2 ) ) ( P = 0.031 ) and higher progesterone ( P < 0.001 ) levels were found with rFSH , even after adjusting for follicular response . The distribution of hypo- , iso- and hyper-echogenic endometrium showed a significant ( P = 0.023 ) shift towards the hyperechogenic pattern after rFSH treatment . The ongoing pregnancy rate per cycle was 27 % with HP-hMG and 22 % with rFSH [ odds ratio ( 95 % confidence interval ) : 1.25 ( 0.89 - 1.75 ) ] . CONCLUSION Superiority of HP-hMG over rFSH in ongoing pregnancy rate could not be concluded from this study , but non-inferiority was established . Pharmacodynamic differences in follicular development , oocyte/embryo quality , endocrine response and endometrial echogenicity exist between HP-hMG and rFSH preparations , which may be relevant for treatment outcome Background To determine the effect of higher progesterone ( P ) level on  endometrial receptivity . Methods This was a prospect i ve analysis conducted in the Reproductive Medical Center of Peking University Third Hospital . All patients received IVF treatment and canceled embryo transfer  in the same cycle and were divided into group 1 ( normal P ; 7 patients ) and group 2 ( elevated P ; 12 patients ) .  Endometrial biopsies were performed 6 days after oocyte retrieval . The global miRNA and mRNA gene expressions in endometrial biopsies were investigated with a V4.0 miRNA probe and 22 K Human Genome Array . Fold ratios were derived to compare gene regulation between the groups . Spp1 and Ang gene expression was selected to verify the array results by RT-PCR and the protein expression of osteopontin and VEGF was determined using an immunohistochemical method . Results There were 4 miRNA ( all down-regulated ) and 22 mRNA ( 13 up-regulated and 9 down-regulated ) exhibiting differential expression between the groups on the microRNA and microarray chips . miRNA-451 , Spp1 , and Ang expression in RT-PCR verified the array results . Osteopontin and VEGF were also shown to have positive expression in the endometrium . Conclusions Data from microRNA and microarray analysis suggests dissimilar endometrial receptivity in patients with high P levels on the day of hCG , and elevated osteopontin and decreased VEGF had  poor pregnancy rates The aim of the present study was to evaluate the relationship between serum progesterone level on the day of human chorionic gonadotropin ( hCG ) administration ( day 0 ) and pregnancy rate among patients undergoing in vitro fertilization and embryo transfer .  Serum progesterone levels were analyzed retrospectively in 160 cycles . In 56 women ovarian stimulation was induced by gonadotropins only ( group A ) . In 104 cases a gonadotropin releasing hormone ( GnRH ) analog was given prior to gonadotropin administration ( group B ) . At least three embryos were transferred in all cases . A significantly ( p < 0.01 ) higher serum progesterone level ( > or = 1 ng/ml ) on day 0 was observed in the 43 patients of group A who did not conceive compared with the 13 who conceived . No significant difference in serum progesterone levels on day 0 was found between the 37 patients of group B who conceived and the 67 who did not . The pregnancy rate ( 0.36 ) in group B was significantly ( p < 0.05 ) higher than that in group A ( 0.23 ) . However , the pregnancy rate ( 0.35 ) in patients in group A with low progesterone levels ( < or = 1 ng/ml ) was not significantly lower than that in group B. We demonstrated that elevated progesterone levels ( > or = 1 ng/ml ) on day 0 in patients receiving stimulation with gonadotropin only , might be detrimental to pregnancy . In view of these results , we suggest that early oocyte retrieval should be considered in patients whose progesterone level on the day of hCG administration exceeds 1 ng/ml following stimulation with gonadotropin only OBJECTIVE To determine the prevalence and the effect of premature luteinization in  GnRH antagonist IVF-ET cycles . DESIGN Prospect i ve observational study . SETTING In vitro fertilization-embryo transfer ( IVF-ET ) program at the Instituto Valenciano de Infertilidad . PATIENT(S ) Eighty-one infertile patients undergoing controlled ovarian hyperstimulation with gonadotropins and GnRH antagonist for IVF-ET .  INTERVENTION(S ) Gonadotropin-releasing hormone ( GnRH ) antagonist was administered from stimulation day 6 . Serum P , E(2 ) , and LH were determined on the day of hCG administration . MAIN OUTCOME MEASURE(S ) Cycles were grouped according to serum P level on the day of hCG administration ( < 1.2 ng/mL or > or = 1.2 ng/mL ) . Clinical pregnancy and implantation rates were determined . RESULT ( S ) The incidence of premature luteinization was 38.3 % . Total recombinant FSH dose and stimulation days differed significantly between the groups 
    Output:
    
Based on the analysis of more than 60 000 cycles , it can be supported that PE on the day of hCG administration is associated with a decreased probability of pregnancy achievement in fresh IVF cycles in women undergoing ovarian stimulation using GnRH analogues and gonadotrophins .
On the other h and , an adverse effect of PE does not seem to be present in frozen-thawed and donor/recipient cycles