***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 
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    Input: OBJECTIVE To determine the incidence of ovarian hyperstimulation syndrome ( OHSS ) in a large series of GnRH antagonist-stimulated cycles and to assess the predictive value of E2 and the number of follicles on the day of hCG administration . DESIGN Prospect i ve cohort study of women undergoing IVF treatment with a GnRH antagonist protocol over a 2-year period . SETTING Tertiary university hospital . PATIENT(S ) One thous and eight hundred one patients who underwent 2,524 cycles . INTERVENTION(S ) Multifollicular ovarian stimulation with recombinant FSH and GnRH antagonist for IVF-ICSI treatment . MAIN OUTCOME MEASURE(S ) Incidence of OHSS in GnRH antagonist cycles , predictive value of E2 , and number of follicles on the day of hCG for OHSS occurrence . RESULT ( S ) Fifty-three patients were hospitalized because of OHSS ( 2.1 % ; 95 % confidence interval [CI]:1.6 - 2.8 ) . Early OHSS presented in 31 patients ( 1.2 % ; 95 % CI : 0.9 - 1.8 ) , whereas the late type was a complication in 22 patients ( 0.9 % ; 95 % CI : 0.5 - 1.3 ) . Late OHSS cases compared with the early OHSS cases always occurred in a pregnancy cycle ( 100 % vs. 40 % ) ; had higher probability of being severe ( 72.7 % vs. 42 % ) , and more often were related to a multiple pregnancy ( 40 % vs. 0 ) . Receiver operating characteristic curve analysis for several E2 concentrations and number of follicles with a diameter of > or = 11 mm revealed that the predictive value of the optimal threshold of > or = 13 follicles ( 85.5 % sensitivity ; 69 % specificity ) was statistically significantly superior to the optimal threshold of 2,560 ng/L for E2 concentrations ( 53 % sensitivity , 77 % specificity ) in identifying patients at risk for OHSS . Considering that severe OHSS represents the most clinical ly significant pattern , the combination of a threshold of > or = 18 follicles and /or E2 of > or = 5,000 ng/L yields a 83 % sensitivity rate with a specificity as high as 84 % for the severe OHSS cases . CONCLUSION ( S ) Clinical ly significant OHSS still remains a limitation of multifollicular ovarian stimulation for IVF even with the use of GnRH antagonist protocol s. The number of follicles can discriminate the patients who are at risk for developing OHSS , whereas E2 concentrations are less reliable for the purpose of prediction . There is more than ever an urgent need for alternative final oocyte maturation-triggering medication Background : The effect of elevated progesterone level on human chorionic gonadotropin ( HCG ) day in in vitro fertilization cycles is controversial . Some suppose that rise in progesterone level seems to have a negative impact on implantation and pregnancy by desynchronizing the endometrium , while others disagree . Objective : To evaluate the superiority of the frozen cycle over fresh cycle on live birth in patients with elevated progesterone level on HCG day . Material s and Methods : In this double-blind , r and omized clinical trial , 72 women undergoing assisted reproductive technology with elevated progesterone level ( ≥1.8 ng/dl ) on HCG day were included . The participants were grouped by fresh versus frozen embryo transfer , r and omly . Finally , the clinical pregnancy and live birth rate were compared . Results : The implantation rate was 21.51 % . The clinical pregnancy rate was 47.22 % in fresh embryo transfer group ( 17/36 ) and 41.66 % in frozen group ( 15/36 ) ( p=0 . 40 ) . The live birth rate was not significantly difference between two groups ( p=0.56 ) . Conclusion : None of the fresh and frozen cycles are superior to the other and we recommend individualizing the decision for each patient . The frozen cycle may impose more emotional stress on patients Background Among women who are undergoing in vitro fertilization ( IVF )  , the transfer of frozen embryos has been shown to result in a higher rate of live birth than the transfer of fresh embryos in those with infertility associated with the polycystic ovary syndrome . It is not known whether frozen‐embryo transfer results in similar benefit in women with infertility that is not associated with the polycystic ovary syndrome . Methods We r and omly assigned 782 infertile women without the polycystic ovary syndrome who were undergoing a first or second IVF cycle to receive either a frozen embryo or a fresh embryo on day 3 . In the frozen‐embryo group , all grade 1 and 2 embryos had been cryopreserved , and a maximum of two embryos were thawed on the day of transfer in the following cycle . In the fresh‐embryo group , a maximum of two fresh embryos were transferred in the stimulated cycle . The primary outcome was ongoing pregnancy after the first embryo transfer . Results After the first completed cycle , ongoing pregnancy occurred in 142 of 391 women ( 36.3 % ) in the frozen‐embryo group and in 135 of 391 ( 34.5 % ) in the fresh‐embryo group ( risk ratio in the frozen‐embryo group , 1.05 ; 95 % confidence interval [ CI ] , 0.87 to 1.27 ; P=0.65 ) . Rates of live birth after the first transfer were 33.8 % and 31.5 % , respectively ( risk ratio , 1.07 ; 95 % CI , 0.88 to 1.31 ) . Conclusions Among infertile women without the polycystic ovary syndrome who were undergoing IVF , the transfer of frozen embryos did not result in significantly higher rates of ongoing pregnancy or live birth than the transfer of fresh embryos . ( Funded by My Duc Hospital ; Clinical Trials.gov number , NCT02471573 . OBJECTIVE To evaluate the effect of frozen embryo transfer on maternal and neonatal complications of singleton and twin pregnancies compared with fresh embryo transfer in women with polycystic ovary syndrome ( PCOS ) . DESIGN A secondary analysis of a multicenter , r and omized , controlled trial comparing live birth after frozen vs. fresh embryo transfer ( FreFro-PCOS ) . SETTING Reproductive medicine centers . PATIENT(S ) A total of 1,508 patients with a diagnosis of PCOS who were undergoing IVF were enrolled . INTERVENTION(S ) On day of oocyte retrieval , eligible patients were r and omized to the fresh or frozen embryo transfer groups . Up to two embryos were transferred in both groups . All pregnancies were followed up until delivery . MAIN OUTCOME MEASURE(S ) Gestational diabetes mellitus , pre-eclampsia , preterm birth , small for gestational age , and large for gestational age . RESULT ( S ) The risks of gestational diabetes mellitus , preterm birth , and small for gestational age were comparable between the frozen and fresh embryo transfer groups in both singleton and twin births . However , singleton infants born after frozen embryo transfer were more likely to be large for gestational age ( 25.2 % vs. 17.5 % ; relative risk 1.44 , 95 % confidence interval 1.01 - 2.07 , P=.044 ) than those born after fresh embryo transfer . Twin pregnancy after frozen embryo transfer had a higher risk of pre-eclampsia ( 12.0 % vs. 2.8 % ; relative risk 4.31 , 95 % confidence interval 1.27 - 14.58 , P=.009 ) than those after fresh embryo transfer . CONCLUSION ( S ) In women with PCOS , frozen embryo transfer result ed in an increased risk of large for gestational age in singleton pregnancy and a higher risk of pre-eclampsia in twin pregnancy . CLINICAL TRIAL REGISTRATION NUMBER NCT01841528 STUDY QUESTION Is there a relationship between serum progesterone ( P ) and endometrial volume on the day of embryo transfer ( ET ) with ongoing pregnancy rate ( OPR ) in artificial endometrium preparation cycles ? SUMMARY ANSWER Patients with serum P < 9.2 ng/ml on the day of ET had a significantly lower OPR but endometrial volume was not related with OPR . WHAT IS KNOWN ALREADY A window of optimal serum P levels during the embryo implantation period has been described in artificial endometrium preparation cycles . A very low endometrial volume is related to poor reproductive outcome . STUDY DESIGN , SIZE , DURATION Prospect i ve cohort study with 244 patients who underwent ET in an oocyte donation cycle after an artificial endometrial preparation cycle with estradiol valerate and vaginal micronized progesterone ( 400 mg/12 h ) . The study period went from 22 February 2016 to 25 October 2016 ( 8 months ) . Sample size was calculated to detect a 20 % difference in OPR ( 35 - 55 % ) between two groups according to serum P levels in a two-sided test ( 80 % statistical power , 95 % confidence interval ( CI ) ) . PARTICIPANTS / MATERIAL S , SETTING , METHODS Patients undergoing their first/second oocyte donation cycle , aged < 50 , BMI < 30 kg/m2 , triple layer endometrium > 6.5 mm and 1 - 2 good quality transferred blastocysts . A private infertility centre .  Serum P determination and 3D ultrasound of uterine cavity  were performed on the day of ET . Endometrial volume measurements were taken using a virtual organ computer-aided analysis ( VOCAL ™ ) system . The primary endpoint was OPR beyond pregnancy week 12 . MAIN RESULTS AND ROLE OF CHANCE About 211 of the 244 recruited patients fulfilled all the inclusion /exclusion criteria . Mean serum P on the day of embryo transfer was 12.7 ± 5.4 ng/ml ( Centiles 25 , 9.2 ; 50 , 11.8 ; 75,15.8 ) . OPRs according to serum P quartiles were : Q1 : 32.7 % ; Q2 : 49.1 % ; Q3 : 58.5 % ; Q4 : 50.9 % . The OPR of Q1 was significantly lower than Q2-Q4 : 32.7 % versus 52.8 % ; P = 0.016 ; RR ( 95 % CI ) : 0.62 ( 0.41 - 0.94 ) . The mean endometrial volume was 3.4 ± 1.9 ml . Serum P on the day of ET did not correlate with endometrial volume . A logistic regression analysis , adjusted for all the potential confounders , showed that OPR significantly lowered between women with serum P < 9.2 ng/ml versus ≥9.2 ng/ml ( OR : 0.297 ; 95%CI : 0.113 - 0.779 ) ; P = 0.013 . The ROC curve showed a significant predictive value of serum P levels on the day of ET for OPR , with an AUC ( 95%CI ) = 0.59 ( 0.51 - 0.67 ) . LIMITATIONS , REASONS FOR CAUTION Only the women with normal uterine cavity , appropriate endometrial thickness and good quality blastocysts transfer were included . Extrapolation to an unselected population or to other routes and /or doses of administering P needs to be vali date d. The role of endometrial volume could not be fully defined as very few patients presented a very low volume . WIDER IMPLICATION S OF THE FINDINGS The present study suggests a minimum threshold of serum P values on the day of ET that needs to be reached in artificial endometrial preparation cycles to optimize outcome . No upper threshold could be defined . STUDY FUNDING /COMPETING INTEREST(S ) None . TRIAL REGISTRATION NUMBER NCT02696694 Background : The use of embryo cryopreservation excludes the possible detrimental effects of ovarian stimulation on the endometrium , and higher reproductive outcomes following this policy have been reported . Moreover , gonadotropin-releasing hormone agonist trigger in gonadotropin-releasing hormone ( GnRH ) antagonist cycles as a substitute for st and ard human chorionic gonadotropin trigger , minimizes the risk of ovarian hyperstimulation syndrome ( OHSS ) in fresh as well as frozen embryo transfer cycles ( FET ) . Objective : To compare the reproductive outcomes and risk of OHSS in fresh vs frozen embryo transfer in high responder patients , undergoing in vitro fertilization triggered with a bolus of GnRH agonist . Material s and Methods : In this r and omized , multi-centre study , 121 women undergoing FET and 119 women undergoing fresh ET  were investigated as regards clinical pregnancy as the primary outcome and the chemical pregnancy , live birth , OHSS development , and perinatal data as secondary outcomes . Results : There were no significant differences between FET and fresh groups regarding chemical ( 46.4 % vs. 40.2 % , p=0.352 ) , clinical ( 35. 
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WIDER IMPLICATION S Although the use of eFET has steadily increased in recent years , a significant increase in LBR with eFET was solely noted in hyper-responders and in patients undergoing PGT-A. Concerning safety , eFET significantly decreases the risk of moderate and severe OHSS , albeit at the expense of an increased risk of pre-eclampsia