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Study Question: Does ovarian stimulation with highly purified (hp)-HMG protect from elevated progesterone in the follicular phase compared to recombinant FSH (r-FSH) cycles through a different regulation of follicular steroidogenesis?, Summary Answer: hp-HMG enhanced the Δ4 pathway from pregnenolone to androstenodione leading to lower serum progesterone at the end of the cycle, while r-FSH promoted the conversion of pregnenolone to progesterone causing higher follicular phase progesterone levels., What Is Known Already: Elevated progesterone in the follicular phase has been related to lower clinical outcome in fresh IVF cycles. Progesterone levels are positively correlated to ovarian response, and some studies have shown that when r-FSH alone is used for ovarian stimulation serum progesterone levels on the day of triggering are higher than when hp-HMG is given. Whether this is caused by a lower ovarian response in hp-HMG cycles or to a difference in follicular steroidogenesis in the two ovarian stimulation regimens has not been well characterized., Study Design, Size, Duration: A randomized controlled trial including 112 oocyte donors undergoing ovarian stimulation with GnRH antagonists and 225 IU/day of r-FSH (n = 56) or hp-HMG (n = 56) was carried out in a university-affiliated private infertility clinic. Subjects were recruited between October 2016 and June 2018., Participants/materials, Setting, Methods: The women were aged 18-35 years with a regular menstrual cycle (25-35 days) and normal ovarian reserve (serum anti-Müllerian hormone (AMH) = 10-30 pMol/l) undergoing ovarian stimulation for oocyte donation. FSH, LH, estradiol (E2), estrone, progesterone, pregnenolone, 17-OH-progesterone, androstenodione, dehidroepiandrostenodione, and testosterone were determined on stimulation Days 1, 4, 6, and 8 and on day of triggering in serum and in follicular fluid. Samples were frozen at -20°C until assay. Total exposures across the follicular phase were compared by polynomic extrapolation., Main Results and the Role of Chance: Subjects in both groups were comparable in terms of age, BMI, and AMH levels. Ovarian response was also similar: 17.5 ± 7.9 (mean ± SD) versus 16.5 ± 7.5 oocytes with r-FSH and hp-HMG, respectively (P = 0.49). Serum progesterone (ng/ml) on day of trigger was 0.46 ± 0.27 in the hp-HMG group versus 0.68 ± 0.50 in the r-FSH group (P = 0.010). Differences for progesterone were also significant on stimulation days 6 and 8. The pregnenolone: progesterone ratio was significantly increased in the r-FSH group from stimulation day 8 to the day of trigger (P = 0.019). Serum androstenodione (ng/ml) on day of trigger was 3.0 ± 1.4 in the hp-HMG group versus 2.4 ± 1.1 in the r-FSH group (P = 0.015). Differences in adrostenodione were also significant on stimulation Day 8. The pregnenolone:androstenodione ratio was significantly higher in the hp-HMG group (P = 0.012) on Days 6 and 8 and trigger. There were no other significant differences between groups. Follicular fluid E2, FSH, LH, dehidroepioandrostenodione, androstenodione, and testosterone were significantly higher in the hp-HMG than r-FSH group. No differences were observed for progesterone, estrone, 17-OH-progesterone, and pregnenolone in follicular fluid., Limitations, Reasons for Caution: All women included in the study were young, not infertile, and had a normal BMI and a good ovarian reserve. The findings might be different in other patient subpopulations. Hormone analyses with immunoassays are subject to intra-assay variations that may influence the results., Wider Implications of the Findings: Stimulation with hp-HMG may prevent progesterone elevation at the end of the follicular phase because of a different follicular steroidogenesis pathway, regardless of ovarian response. This should be considered, particularly in patients at risk of having high progesterone levels at the end of the follicular phase when a fresh embryo transfer is planned., Study Funding/competing Interest(s): Roche Diagnostics provided unrestricted funding for all serum and follicular fluid hormone determinations. J.L.R., M.M., and A.P. have nothing to declare. E.B. has received consulting fees from Ferring, Merck, Gedeon Richter, and Roche and has participated in a research cooperation with Gedeon-Richter. In addition, the author has participated in speakers' bureau and received fees from Ferring, Gedeon Richter, Merck, and Roche. P.A. has received consulting fees from MSD and has participated in speakers' bureau and received fees from Ferring. P.A. also declares travel/meeting support from MSD. E.L. has received consulting fees from Ferring and MSD. In addition, the author has participated in a research cooperation with Gedeon-Richter. Also, the author has participated in speakers' bureau and received fees from Ferring and IBSA, as well as travel/meeting support from IBSA and Gedeon Richter. E.B., P.A., and E.L. also own stocks in IVIRMA Valencia., Trial Registration Number: NCT: NCT02738580., Trial Register Date: 19 February 2016., Date of First Patient’s Enrolment: 03 October 2016., (© The Author(s) 2023. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Study Question: What is the recommended management for couples presenting with unexplained infertility (UI), based on the best available evidence in the literature?, Summary Answer: The evidence-based guideline on UI makes 52 recommendations on the definition, diagnosis, and treatment of UI., What Is Known Already: UI is diagnosed in the absence of any abnormalities of the female and male reproductive systems after 'standard' investigations. However, a consensual standardization of the diagnostic work-up is still lacking. The management of UI is traditionally empirical. The efficacy, safety, costs, and risks of treatment options have not been subjected to robust evaluation., Study Design, Size, Duration: The guideline was developed according to the structured methodology for ESHRE guidelines. Following formulation of key questions by a group of experts, literature searches, and assessments were undertaken. Papers written in English and published up to 24 October 2022 were evaluated., Participants/materials, Setting, Methods: Based on the available evidence, recommendations were formulated and discussed until consensus was reached within the guideline development group (GDG). Following stakeholder review of an initial draft, the final version was approved by the GDG and the ESHRE Executive Committee., Main Results and the Role of Chance: This guideline aims to help clinicians provide the best care for couples with UI. As UI is a diagnosis of exclusion, the guideline outlined the basic diagnostic procedures that couples should/could undergo during an infertility work-up, and explored the need for additional tests. The first-line treatment for couples with UI was deemed to be IUI in combination with ovarian stimulation. The place of additional and alternative options for treatment of UI was also evaluated. The GDG made 52 recommendations on diagnosis and treatment for couples with UI. The GDG formulated 40 evidence-based recommendations-of which 29 were formulated as strong recommendations and 11 as weak-10 good practice points and two research only recommendations. Of the evidence-based recommendations, none were supported by high-quality evidence, one by moderate-quality evidence, nine by low-quality evidence, and 31 by very low-quality evidence. To support future research in UI, a list of research recommendations was provided., Limitations, Reasons for Caution: Most additional diagnostic tests and interventions in couples with UI have not been subjected to robust evaluation. For a large proportion of these tests and treatments, evidence was very limited and of very low quality. More evidence is required, and the results of future studies may result in the current recommendations being revised., Wider Implications of the Findings: The guideline provides clinicians with clear advice on best practice in the care of couples with UI, based on the best evidence currently available. In addition, a list of research recommendations is provided to stimulate further studies in the field. The full guideline and a patient leaflet are available in www.eshre.eu/guideline/UI., Study Funding/competing Interest(s): The guideline was developed by ESHRE, who funded the guideline meetings, literature searches, and dissemination of the guideline in collaboration with the Monash University led Australian NHMRC Centre of Research Excellence in Women's Health in Reproductive Life (CREWHIRL). The guideline group members did not receive any financial incentives; all work was provided voluntarily. D.R. reports honoraria from IBSA and Novo Nordisk. B.A. reports speakers' fees from Merck, Gedeon Richter, Organon and Intas Pharma; is part of the advisory board for Organon Turkey and president of the Turkish Society of Reproductive Medicine. S.B. reports speakers' fees from Merck, Organon, Ferring, the Ostetric and Gynaecological Society of Singapore and the Taiwanese Society for Reproductive Medicine; editor and contributing author, Reproductive Medicine for the MRCOG, Cambridge University Press; is part of the METAFOR and CAPE trials data monitoring committee. E.B. reports research grants from Roche diagnostics, Gedeon Richter and IBSA; speaker's fees from Merck, Ferring, MSD, Roche Diagnostics, Gedeon Richter, IBSA; E.B. is also a part of an Advisory Board of Ferring Pharmaceuticals, MSD, Roche Diagnostics, IBSA, Merck, Abbott and Gedeon Richter. M.M. reports consulting fees from Mojo Fertility Ltd. R.J.N. reports research grant from Australian National Health and Medical Research Council (NHMRC); consulting fees from Flinders Fertility Adelaide, VinMec Hospital Hanoi Vietnam; speaker's fees from Merck Australia, Cadilla Pharma India, Ferring Australia; chair clinical advisory committee Westmead Fertility and research institute MyDuc Hospital Vietnam. T.P. is a part of the Research Council of Finland and reports research grants from Roche Diagnostics, Novo Nordics and Sigrid Juselius foundation; consulting fees from Roche Diagnostics and organon; speaker's fees from Gedeon Richter, Roche, Exeltis, Organon, Ferring and Korento patient organization; is a part of NFOG, AE-PCOS society and several Finnish associations. S.S.R. reports research grants from Roche Diagnostics, Organon, Theramex; consulting fees from Ferring Pharmaceuticals, MSD and Organon; speaker's fees from Ferring Pharmaceuticals, MSD/Organon, Besins, Theramex, Gedeon Richter; travel support from Gedeon Richter; S.S.R. is part of the Data Safety Monitoring Board of TTRANSPORT and deputy of the ESHRE Special Interest Group on Safety and Quality in ART; stock or stock options from IVI Lisboa, Clínica de Reprodução assistida Lda; equipment/medical writing/gifts from Roche Diagnostics and Ferring Pharmaceuticals. S.K.S. reports speakers' fees from Merck, Ferring, MSD, Pharmasure. HRV reports consulting and travel fees from Ferring Pharmaceuticals. The other authors have nothing to disclose., Disclaimer: This guideline represents the views of ESHRE, which were achieved after careful consideration of the scientific evidence available at the time of preparation. In the absence of scientific evidence on certain aspects, a consensus between the relevant ESHRE stakeholders has been obtained. Adherence to these clinical practice guidelines does not guarantee a successful or specific outcome, nor does it establish a standard of care. Clinical practice guidelines do not replace the need for application of clinical judgment to each individual presentation, nor variations based on locality and facility type. ESHRE makes no warranty, express or implied, regarding the clinical practice guidelines and specifically excludes any warranties of merchantability and fitness for a particular use or purpose. (Full disclaimer available at www.eshre.eu/guidelines.)., (© The Author(s) 2023. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology.)

Study Question: Do children born after vitrified-thawed embryo transfers (ETs) using donated oocytes have worse perinatal outcomes when compared with fresh ET?, Summary Answer: No significant difference in birthweight and prematurity rates between fresh or frozen embryo transfers (FETs) in newborns after oocyte donation was found., What Is Known Already: Autologous singletons born after fresh ET have been previously associated with higher rates of preterm birth and low birthweight, while FETs seem to confer a higher risk of hypertensive disorders during pregnancy and macrosomia. However, studies comparing these outcomes using autologous oocytes are unable to adequately disentangle the putative detrimental consequences of embryo vitrification from the possible effects that ovarian stimulation and endometrial preparation may have on endometrial receptivity prior to ET. The oocyte donation model is, for this reason, a more appropriate setting to study these hypotheses; however so far, the information available regarding neonatal outcomes in this patient population is limited to either small and/or heterogeneous studies., Study Design, Size, Duration: We performed a multicentre retrospective cohort study including 5848 singletons born between 2009 and February 2020 following oocyte donation and single blastocyst transfer, subdivided according to whether a fresh ET or FET was performed. We also performed two additional sensitivity analyses, subgrouping the sample according to the type of endometrial preparation (natural versus artificial) and whether the donated oocytes had previously been vitrified or not., Participants/materials, Setting, Methods: Patients with a first singleton livebirth after single blastocyst transfer were compared using multivariable regression analysis to account for potential confounding factors. The primary outcome was birthweight. Secondary outcomes were birthweight z-scores and percentiles, small/large for gestational age, gestational age at delivery, gender, prematurity (<37 weeks and <32 weeks), neonatal morbidity (Apgar scores and need for neonatal intensive care) and maternal morbidity (gestational hypertensive disorders, gestational diabetes and caesarean delivery)., Main Results and the Role of Chance: There was no significant difference between the fresh ET and FET groups in terms of mean birthweight (3215 g versus 3200 g) and birthweight z-scores (0.03 versus 0.1), in both the unadjusted and confounder-adjusted models. However, artificial endometrial preparation was associated with a higher birthweight (3220 g versus 3105 g) and birthweight z-scores (0.06 versus -0.13) when compared with a transfer in a natural cycle. Although a 1-day statistically significant difference in gestational age at birth (275 versus 274 days) was detected, premature birth rates (<37 weeks) did not vary significantly between groups (9.9% and 11.2% for fresh ET and FET, respectively). No other statistically significant differences were found in the remaining neonatal and maternal outcomes studies between the fresh ET and FET groups., Limitations, Reasons for Caution: This study is limited by its retrospective design and lack of information regarding congenital malformations. Moreover, the sample selection criteria that were used may limit the generalizability of our results., Wider Implications of the Findings: Perinatal outcomes did not seem to be affected significantly by the embryo vitrification process in an oocyte donation model. Hence, other factors may contribute to the hindered perinatal outcomes described in ART, particularly the potential effect that ovarian stimulation and endometrial preparation may have on endometrial receptivity., Study Funding/competing Interest(s): No specific funding was obtained for this study. All authors have no conflicts to declare., Trial Registration Number: N/A., (© The Author(s) 2022. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Study Question: Is there a relationship between serum and endometrial progesterone (P4) levels, including P4 and metabolites (oestrone, oestradiol and 17α-hydroxyprogesterone), and endometrial receptivity?, Summary Answer: Serum P4 levels were not correlated with endometrial P4, nor associated with endometrial receptivity as determined by the ERA® test; however, endometrial P4 and 17α-hydroxyprogesterone levels were positively correlated and related to endometrial receptivity by ERA., What Is Known Already: Acquisition of endometrial receptivity is governed by P4, which induces secretory transformation. A close relationship between serum P4 and pregnancy outcome is reported for hormone replacement therapy (HRT) cycles. However, the relationship between serum and uterine P4 levels has not been described, and it is unknown whether uterine receptivity depends more on serum or uterine P4 levels., Study Design, Size, Duration: A prospective cohort study was performed during March 2018-2019 in 85 IVF patients undergoing an evaluation-only HRT cycle with oestradiol valerate (6 mg/day) and micronised vaginal progesterone (400 mg/12 h)., Participants/materials, Setting, Methods: Patients were under 50 years of age, had undergone at least one failed IVF cycle, had no uterine pathology, and had adequate endometrial thickness (> 6.5 mm). The study was conducted at IVI Valencia and IVI Foundation. An endometrial biopsy and a blood sample were collected after 5 days of P4 vaginal treatment. Measures included serum P4 levels, ERA®-based evaluation of endometrial receptivity, and endometrial P4 levels along with metabolites (oestrone, oestradiol and 17α-hydroxyprogesterone) measured by ultra-performance liquid chromatography-tandem mass spectrometry., Main Results and the Role of Chance: Seventy-nine women were included (mean age: 39.9 ± 4.6, BMI: 24.2 ± 3.9 kg/m2, endometrial thickness: 8.2 ± 1.4 mm). The percentage of endometria indicated as receptive by ERA® was 40.5%. When comparing receptive versus non-receptive groups, no differences were observed in baseline characteristics nor in steroid hormones levels in serum or endometrium. No association between serum P4 and endometrial steroid levels or ERA result was found (P < 0.05). When the population was stratified according to metabolite concentration levels, endometrial P4 and 17α-hydroxyprogesterone were significantly associated with endometrial receptivity (P < 0.05). A higher proportion of receptive endometria by ERA was observed when endometrial P4 levels were higher than 40.07 µg/ml (relative maximum) and a lower proportion of receptive endometria was associated with endometrial 17α-hydroxyprogesterone lower than 0.35 ng/ml (first quartile). A positive correlation R2 = 0.67, P < 0.001 was observed between endometrial P4 and 17α-hydroxyprogesterone levels., Limitations, Reasons for Caution: This study did not analyse pregnancy outcomes. Further, the findings can only be extrapolated to HRT cycles with micronised vaginal progesterone for luteal phase support., Wider Implications of the Findings: Our findings suggest that the combined benefits of different routes of progesterone administration for luteal phase support could be leveraged to ensure an adequate concentration of progesterone both in the uterus and in the bloodstream. Further studies will confirm whether this method can optimise both endometrial receptivity and live birth rate. Additionally, targeted treatment to increase P4 endometrial levels may normalise the timing of the window of implantation without needing to modify the progesterone administration day., Study Funding/competing Interest(s): This research was supported by the IVI-RMA Valencia (1706-VLC-051-EL) and Consellería d'Educació, Investigació, Cultura, i esport Generalitat Valenciana (Valencian Government, Spain, GV/2018//151). Almudena Devesa-Peiro (FPU/15/01398) and Cristina Rodriguez-Varela (FPU18/01657) were supported by the FPU program fellowship from the Ministry of Science, Innovation and Universities (Spanish Government). P.D.-G. is co-inventor on the ERA patent, with non-economic benefits. The other authors have no competing interests., Trial Registration Number: NCT03456375., (© The Author(s) 2021. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) play complementary roles in follicle development and ovulation via a complex interaction in the hypothalamus, anterior pituitary gland, reproductive organs, and oocytes. Impairment of the production or action of gonadotropins causes relative or absolute LH and FSH deficiency that compromises gametogenesis and gonadal steroid production, thereby reducing fertility. In women, LH and FSH deficiency is a spectrum of conditions with different functional or organic causes that are characterized by low or normal gonadotropin levels and low oestradiol levels. While the causes and effects of reduced LH and FSH production are very well known, the notion of reduced action has received less attention by researchers. Recent evidence shows that molecular characteristics, signalling as well as ageing, and some polymorphisms negatively affect gonadotropin action. These findings have important clinical implications, in particular for medically assisted reproduction in which diminished action determined by the afore-mentioned factors, combined with reduced endogenous gonadotropin production caused by GnRH analogue protocols, may lead to resistance to gonadotropins and, thus, to an unexpected hypo-response to ovarian stimulation. Indeed, the importance of LH and FSH action has been highlighted by the International Committee for Monitoring Assisted Reproduction Technologies (ICMART) in their definition of hypogonadotropic hypogonadism as gonadal failure associated with reduced gametogenesis and gonadal steroid production due to reduced gonadotropin production or action. The aim of this review is to provide an overview of determinants of reduced FSH and LH action that are associated with a reduced response to ovarian stimulation., (© The Author(s) 2021. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology.)

Study Question: Is there a serum progesterone (P) threshold on the day of embryo transfer (ET) in artificial endometrium preparation cycles below which the chances of ongoing pregnancy are reduced?, Summary Answer: Serum P levels <8.8 ng/ml on the day of ET lower ongoing pregnancy rate (OPR) in both own or donated oocyte cycles., What Is Known Already: We previously found that serum P levels <9.2 ng/ml on the day of ET significantly decrease OPR in a sample of 211 oocyte donation recipients. Here, we assessed whether these results are applicable to all infertile patients under an artificial endometrial preparation cycle, regardless of the oocyte origin., Study Design, Size, Duration: This prospective cohort study was performed between September 2017 and November 2018 and enrolled 1205 patients scheduled for ET after an artificial endometrial preparation cycle with estradiol valerate and micronized vaginal P (MVP, 400 mg twice daily)., Participants/materials, Setting, Methods: Patients ≤50 years old with a triple-layer endometrium ≥6.5 mm underwent transfer of one or two blastocysts. A total of 1150 patients treated with own oocytes without preimplantation genetic testing for aneuploidies (PGT-A) (n = 184), own oocytes with PGT-A (n = 308) or donated oocytes (n = 658) were analyzed. The primary endpoint was the OPR beyond pregnancy week 12 based on serum P levels measured immediately before ET., Main Results and the Role of Chance: Women with serum P levels <8.8 ng/ml (30th percentile) had a significantly lower OPR (36.6% vs 54.4%) and live birth rate (35.5% vs 52.0%) than the rest of the patients. Multivariate logistic regression showed that serum P < 8.8 ng/ml was an independent factor influencing OPR in the overall population and in the three treatment groups. A significant negative correlation was observed between serum P levels and BMI, weight and time between the last P dose and blood tests and a positive correlation was found with age, height and number of days on HRT. Multivariate logistic regression showed that only body weight was an independent factor for presenting serum P levels <8.8 ng/ml. Obstetrical and perinatal outcomes did not differ in patients with ongoing pregnancy regardless of serum P levels being above/below 8.8 ng/ml., Limitations, Reasons for Caution: Only women with MVP were included. Extrapolation to other P administration forms needs to be validated., Wider Implications of the Findings: This study identified the threshold of serum P as 8.8 ng/ml on the day of ET for artificial endometrial preparation cycles necessary to optimize outcomes, in cycles with own or donated oocytes. One-third of patients receiving MVP show inadequate levels of serum P that, in turn, impact the success of the ART cycle. Monitoring P levels in the mid-luteal phase is recommended when using MVP to adjust the doses according to the needs of the patient., Study Funding/competing Interest(s): None., Trial Registration Number: NCT03272412., (© The Author(s) 2020. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

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: Prospective 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/materials, 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 validated. The role of endometrial volume could not be fully defined as very few patients presented a very low volume., Wider Implications 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., (© The Author 2017. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com)

Study Question: What is the final hormonal milieu of pre-ovulatory follicles of low-responder (LR) patients undergoing unstimulated cycles?, Summary Answer: Neither androgen secretion nor LH was impaired in pre-ovulatory follicles of LR women., What Is Known Already: Therapies currently used to improve ovarian response in LR women have an impact on the final hormonal follicular milieu, and these changes are believed to be partially responsible for determining the success rate in these women. Surprisingly, as far as we know, there is no report of the final hormonal profile of LR women undergoing unstimulated cycles or evidence that follicular androgen secretion in LR women is impaired., Study Design, Size and Duration: A prospective case-control study including 94 women, 36 normal controls and 58 LR patients (19 Young ≤ 35 years LR and 39 Aged >35 years LR) from 2009 to 2011., Participants/materials, Setting and Methods: Fifty-eight LR women were divided into two groups: Young LR (age ≤ 35; n = 19) and Aged LR (ALR; age >35; n = 39). The control group (group C) comprised 36 egg donors undergoing an unstimulated cycle in our IVF unit. Serum and follicular fluid hormonal concentrations for estradiol (E₂), progesterone, testosterone and androstendione were measured. The spindle parameters of metaphase II oocytes generated from these groups were also analysed., Main Results and the Role of Chance: Pre-ovulatory follicles from LR patients had similar androgenic and LH concentrations to those observed in the control group. However, higher intrafollicular concentrations of FSH and progesterone were observed in ALR. Moreover, no differences were found for the spindle evaluation of oocytes between groups by the Oosight technology., Limitations, Reasons for Caution: The controls were younger and had a lower BMI than the LR women. The sample size available restricted statistical power., Wider Implications of the Findings: This study suggests that the problem with LR women is not the final pre-ovulatory follicular androgen concentration since this is similar to normal responders, but in the ability to respond to controlled ovarian stimulation protocols. Therefore, efforts should be focused on long-interval androgen priming to potentially increase the recruitment of small antral follicles rather than increasing the intraovarian androgen levels within the current cycle., Study Funding/competing Interest: The present project has been supported by the R+D programme from the Generalitat Valenciana (Regional Valencian Government) IMPIVA MIDTF/2010/95. The authors have no conflict of interest to declare.

Background: Elevated serum progesterone levels at the end of the follicular phase in controlled ovarian stimulation (COS) leads to a poorer ongoing pregnancy rate in IVF cycles due to reduced endometrial receptivity. The objective of this study was to use microarray technology to compare endometrial gene expression profiles at the window of implantation according to the levels of circulating progesterone., Methods: For this prospective cohort study, microarray data were obtained from endometrial biopsies from 12 young healthy oocyte donors undergoing COS with pituitary suppression by either gonadotrophin-releasing hormone (GnRH) agonists or antagonists, and recombinant FSH. On the day of recombinant chorionic gonadotrophin (rCG) administration, six women had serum progesterone levels (P) >1.5 ng/ml (study group) and six had serum P levels <1.5 ng/ml (control group). Endometrial samples were collected using a Pipelle catheter 7 days after the rCG injection., Results: Using the parametric test, we identified 140 genes significantly dysregulated (64 up- and 76 down-regulated) in the study group endometria compared with the control endometria, regardless of the GnRH analogue employed. These genes are related to cell adhesion, developmental processes, the immune system and others, which are all required for normal endometrial function development. Of the 25 gene targets previously proposed as markers for endometrial receptivity, 13 appeared over-regulated in the study group., Conclusions: Our results reveal that elevated progesterone levels on the day of rCG administration can induce significant alterations in the gene expression profile of the endometrium.

Background: The influence of elevated serum progesterone levels during in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles on pregnancy rates is a matter of continued debate among fertility clinicians. Efforts to resolve this question have been impeded by the various assays used to measure progesterone and the different, arbitrary threshold values for defining 'high' progesterone levels., Methods: A non-interventional, retrospective, observational, single-centre cohort study evaluated the relationship between serum progesterone levels on the day of human chorionic gonadotrophin (hCG) administration and the ongoing pregnancy rate in 4032 patients undergoing IVF/ICSI cycles using gonadotrophin-releasing hormone (GnRH) analogues for pituitary down-regulation., Results: Ongoing pregnancy rates were inversely associated with serum progesterone levels on the day of hCG (P < 0.001 for overall trend), irrespective of the GnRH analogue used for pituitary down-regulation. Patients with serum progesterone levels < or = 1.5 ng/ml had significantly higher ongoing pregnancy rates than those with progesterone levels >1.5 ng/ml (31.0 versus 19.1%; P = 0.00006); odds ratio, 0.53 (95% confidence interval, 0.38-0.72). Multivariate regression analysis showed that daily follicle-stimulating hormone dose, number of oocytes and estradiol values on the day of hCG administration were positively associated with progesterone levels (P < 0.0001 for all). Serum progesterone levels were significantly greater in women treated with GnRH agonists (n = 1177) versus antagonists (n = 2855; 0.84 +/- 0.67 versus 0.75 +/- 0.66 ng/ml; P = 0.0003)., Conclusions: Elevated serum progesterone levels on the day of hCG administration is associated with reduced ongoing pregnancy rates. In particular, serum progesterone levels of >1.5 ng/ml were associated with lower ongoing pregnancy rates following IVF/ICSI cycles irrespective of the GnRH analogue used for pituitary down-regulation.

Background: Highly purified hMG (hp-hMG) has recently shown better cycle outcome than the recombinant FSH (rFSH) when compared in GnRH agonist long protocol cycles. However, they have not yet been compared in GnRH antagonist cycles., Methods: A RCT comparing the ongoing pregnancy rate (primary end-point) in 280 patients undergoing IVF/ICSI after stimulation with hp-hMG or rFSH controlled with a GnRH antagonist., Results: No significant differences were observed between hp-hMG and rFSH in terms of the ongoing pregnancy rate per started cycle (35.0 versus 32.1%, respectively; P = 0.61); relative risk: 1.09 (95% confidence interval: 0.78-1.51; risk difference: 2.9%). No differences were observed for implantation, clinical pregnancy and pregnancy loss rates. More oocytes were obtained from patients receiving rFSH then hMG (14.4 +/- 8.1 versus 11.3 +/- 6.0, respectively; P = 0.001). Estradiol was higher at the end of stimulation in the hp-hMG group (P = 0.02), whereas progesterone was higher in patients stimulated with rFSH (P < 0.001)., Conclusions: A similar outcome was observed for hp-hMG and rFSH when used for stimulation in GnRH antagonist cycles. However, some differences were found in ovarian response in terms of oocyte yield and hormonal profile. Clinical Trials.gov, Trial Registration Number: NCT00669786.

Background: Several evidences indicate that premature luteinization (PL) may affect IVF outcome. The primary end-point of the present study was to verify the effect of PL on the pregnancy rate (PR) of our oocyte-donation programme., Methods: PL was defined as serum progesterone > or = 1.2 ng/ml on the day of HCG. We analysed retrospectively 240 oocyte-donation cycles in which 120 women donated twice, with PL in the first donation cycle and no PL in the following one, acting as its own control. Recipients (n = 240) were divided in two groups according to the presence of PL (n = 120) or not (n = 120). Both groups were compared regarding donor cycle parameters and recipient cycle outcome., Results: There was no difference in PR between the groups (55.7 versus 54.4%, respectively). The number of total oocytes (18.2 +/- 0.6 versus 20.8 +/- 0.6; P = 0.003) and the number of mature oocytes retrieved (16.9 +/- 0.6 versus 19.4 +/- 0.6; P = 0.005) were different among donors with progesterone < 1.2 ng/ml and PL, respectively. There were no differences between the oocyte recipients in fertilization, cleavage, embryo division on day 3, blastocyst development or fragmentation rates. The number of embryos transferred, number of embryos cryopreserved, and implantation and miscarriage rates were similar between the groups., Conclusion: PL does not appear to have a negative impact on ongoing PR in our oocyte-donation programme.

Background: This descriptive study evaluates the impact on endometrial development of standard and high doses of a GnRH antagonist in stimulated cycles compared with GnRH agonist and natural cycles., Methods: Thirty-one oocyte donors were treated with a combination of rFSH and 0.25 mg/day ganirelix (standard dose), 2 mg/day ganirelix (high dose) or 0.6 mg/day buserelin (long protocol). Vaginal progesterone (200 mg/day) was administered in the luteal phase. Endometrial biopsies were performed 2 and 7 days after HCG administration. Additional biopsies were carried out in a subset of 12 subjects, 2 and 7 days following the LH peak of their previous natural cycle. Biopsies were evaluated histologically and by scanning electron microscopy. Gene expression profiles were also studied., Results: At HCG +2, all the parameters studied were similar in all the groups and comparable to those observed in the natural cycle. At HCG +7, endometrial dating, steroid receptors and the presence of pinopodes were comparable in both GnRH antagonist groups and in the natural cycle. In buserelin group, endometrial dating and pinopode expression suggested an arrested endometrial development. For window of implantation genes, expression patterns were closer to those in the natural cycle following standard- or high-dose ganirelix than after buserelin administration., Conclusion: No relevant alteration was observed in the endometrial development in the early and mid-luteal phases in women undergoing controlled ovarian stimulation for oocyte donation following daily treatment with a standard- or high-dose GnRH antagonist. In addition, the endometrial development after GnRH antagonist mimics the natural endometrium more closely than after GnRH agonist.

Background: Intravenous albumin administration has been described for many years as a debatable, but probably useful preventive measure in ovarian hyperstimulation syndrome (OHSS). The present study details the largest randomized controlled trial to date of albumin infusion versus no treatment in IVF patients with a high risk of developing moderate to severe OHSS., Methods: Between March 1999 and February 2002, women undergoing IVF at the IVI Valencia with >20 retrieved oocytes were included. A total of 988 patients was initially enrolled. Immediately after oocyte retrieval, patients were allocated to two groups based on a computer randomization: the first group received 40 g human albumin; the second group received no treatment. Subjects were weighed and a blood analysis performed immediately after oocyte retrieval and again 7 days later. Women were monitored on an outpatient basis until menstruation, or until fetal heart activity was detected. Twelve subjects were excluded due to follow-up loss, leaving 976 women (377 of them oocyte donors), with 488 in each group., Results: No difference was found between the two groups in terms of patient characteristics and outcome. Moderate-severe and severe-only OHSS rates were similar. The incidence of haemoconcentration and liver and renal dysfunction at 7 days after oocyte retrieval was similar in the two groups. In women who developed moderate/severe (n = 66) or only severe (n = 46) OHSS, there was no difference based on prior albumin administration between blood parameters or body weight on the day of oocyte retrieval, 7 days later, and even when comparing variation between both measurements. Moreover, the number of patients with paracentesis, hospital admissions, complications and days of OHSS until resolution did not differ., Conclusions: Albumin infusion on the day of oocyte retrieval is not a useful means of preventing the development of moderate-severe OHSS.