Circadian serum progesterone variations on the day of frozen embryo transfer in a modified natural cycle protocol.

STUDY QUESTION: Is there a circadian variation of serum progesterone (P) on the day of frozen embryo transfer (FET) in a modified natural cycle (mNC)? SUMMARY ANSWER: There is a statistically significant diurnal variation of serum P on the day of a FET in an mNC protocol. WHAT IS KNOWN ALREADY: In recent years, the proportion of FET cycles has increased dramatically. To further optimize pregnancy outcomes after FET, recent studies have focused on serum luteal P levels in both natural and artificially prepared FET cycles. Despite the different cut-off values proposed to define low serum P in the NC, it is generally accepted that lower serum P values (<10 ng/ml) around the day of FET are associated with negative reproductive outcomes. However, a single serum P measurement is not reliable given that P levels are prone to diurnal fluctuations and are impacted by patients' characteristics. STUDY DESIGN, SIZE, DURATION: A prospective cohort study was conducted in a single university-affiliated fertility center, including 22 patients performing a single blastocyst mNC-FET from August 2022 to August 2023. Serum P levels were measured on the day of transfer at 08:00h, 12:00h, 16:00h, and 20:00h. Differences between P levels were compared using the Wilcoxon signed-rank test. The sample size was calculated to detect a difference of 15% between the first and last P measurements with a 5% false-positive rate and a 95% CI. PARTICIPANTS/MATERIALS, SETTING, METHODS: Patients with a normal BMI, between 18 and 40 years old, without uterine diseases were eligible. Patients utilizing donated oocytes were excluded. The mNC-FET protocol involved monitoring the normal ovarian cycle and triggering ovulation with an injection of 250 µg of choriogonadotropin alfa when a pre-ovulatory follicle (16-20 mm diameter) was visualized. The blastocyst was transferred seven days later. The patients were not supplemented with exogenous P at any time before the day of the FET. MAIN RESULTS AND THE ROLE OF CHANCE: The mean age and BMI of the study population were 33.6 ± 3.8 years and 22.7 ± 1.8 kg/m2, respectively. Mean P values at 08:00h, 12:00h, 16:00h, and 20:00h were 14.6 ± 4.5, 14.7 ± 4.1, 12.9 ± 3.5, and 14.6 ± 4.3 ng/ml, respectively. The mean P levels at 16:00h were significantly lower compared to all other time points (P < 0.05: P = 0.007 between P at 8:00h and 16:00h; P = 0.003 between P at 12:00h and 16:00h; P = 0.007 between P at 16:00h and 20:00h). No statistically significant difference was observed between P values at the other time points (P > 0.05: P = 0.88 between P at 8:00h and 12:00h; P = 0.96 between P at 8:00h and 20:00h; P = 0.83 between P at 12:00h and 20:00h). LIMITATIONS, REASONS FOR CAUTION: The study's limitations include the small sample size that may cause a bias when the results are extrapolated to a larger subfertile population undergoing mNC-FET. Ideally, larger prospective trials including a more heterogeneous patient population would be necessary to validate our findings. WIDER IMPLICATIONS OF THE FINDINGS: The current study demonstrates the existence of a diurnal fluctuation of serum P on the day of mNC-FET highlighting the importance of a standardized time point for its measurement. This is especially important for considering clinical actions, such as additional exogenous P supplementation, when encountering P values lower than 10 ng/ml on the day of FET. STUDY FUNDING/COMPETING INTEREST(S): No funding was obtained for the study. The authors have no conflicts of interest to declare regarding the content of the study. TRIAL REGISTRATION NUMBER: NCT05511272.

Progestin primed ovarian stimulation using dydrogesterone from day 7 of the cycle onwards in oocyte donation cycles: a longitudinal study.

RESEARCH QUESTION: Does a progestin-primed ovarian stimulation (PPOS) protocol with dydrogesterone from cycle day 7 yield similar outcomes compared with a gonadotrophin-releasing hormone (GnRH) antagonist protocol in the same oocyte donors? DESIGN: This retrospective longitudinal study included 128 cycles from 64 oocyte donors. All oocyte donors had the same type of gonadotrophin and daily dose in both stimulation cycles. The primary outcome was the number of cumulus-oocyte complexes (COC) retrieved. RESULTS: The number of COC retrieved (mean ± SD 19.7 ± 10.8 versus 19.2 ± 8.3; P = 0.5) and the number of metaphase II oocytes (15.5 ± 8.4 versus 16.2 ± 7.0; P = 0.19) were similar for the PPOS and GnRH antagonist protocols, respectively. The duration of stimulation (10.5 ± 1.5 days versus 10.8 ± 1.5 days; P = 0.14) and consumption of gonadotrophins (2271.9 ± 429.7 IU versus 2321.5 ± 403.4 IU; P = 0.2) were also comparable, without any cases of premature ovulation. Nevertheless, there was a significant difference in the total cost of medication per cycle: €898.3 ± 169.9 for the PPOS protocol versus €1196.4 ± 207.5 (P < 0.001) for the GnRH antagonist protocol. CONCLUSION: The number of oocytes retrieved and number of metaphase II oocytes were comparable in both stimulation protocols, with the advantage of significant cost reduction in favour of the PPOS protocol compared with the GnRH antagonist protocol. No cases of premature ovulation were observed, even when progestin was started later in the stimulation.

Clinical outcomes from ART in predicted hyperresponders: in vitro maturation of oocytes versus conventional ovarian stimulation for IVF/ICSI.

STUDY QUESTION: Do ongoing pregnancy rates (OPRs) differ in predicted hyperresponders undergoing ART after IVM of oocytes compared with conventional ovarian stimulation (OS) for IVF/ICSI? SUMMARY ANSWER: One cycle of IVM is non-inferior to one cycle of OS in women with serum anti-Müllerian hormone (AMH) levels ≥10 ng/ml. WHAT IS KNOWN ALREADY: Women with high antral follicle count and elevated serum AMH levels, indicating an increased functional ovarian reserve, are prone to hyperresponse during ART treatment. To avoid iatrogenic complications of OS, IVM has been proposed as a mild-approach alternative treatment in predicted hyperresponders, including women with polycystic ovary syndrome (PCOS) who are eligible for ART. To date, inferior pregnancy rates from IVM compared to OS have hampered the uptake of IVM by ART clinics. However, it is unclear whether the efficiency gap between IVM and OS may differ depending on the extent of AMH elevation. STUDY DESIGN, SIZE, DURATION: This study is a retrospective cohort analysis of clinical and laboratory data from the first completed highly purified hMG (HP-hMG) primed, non-hCG-triggered IVM or OS (FSH or HP-hMG stimulation in a GnRH antagonist protocol) cycle with ICSI in predicted hyperresponders ≤36 years of age at a tertiary referral university hospital. A total of 1707 cycles were included between January 2016 and June 2022. PARTICIPANTS/MATERIALS, SETTING, METHODS: Predicted hyperresponse was defined as a serum AMH level ≥3.25 ng/ml (Elecsys® AMH, Roche Diagnostics). The primary outcome was cumulative ongoing pregnancy rate assessed 10-11 weeks after embryo transfer (ET). The predefined non-inferiority limit was -10.0%. The analysis was adjusted for AMH strata. Time-to-pregnancy, defined as the number of ET cycles until ongoing pregnancy was achieved, was a secondary outcome. Statistical analysis was performed using a multivariable regression model controlling for potential confounders. MAIN RESULTS AND THE ROLE OF CHANCE: Data from 463 IVM cycles were compared with those from 1244 OS cycles. Women in the IVM group more often had a diagnosis of Rotterdam PCOS (434/463, 93.7%) compared to those undergoing OS (522/1193, 43.8%), were significantly younger (29.5 years versus 30.5 years, P ≤ 0.001), had a higher BMI (25.7 kg/m2 versus 25.1 kg/m2, P ≤ 0.01) and higher AMH (11.6 ng/ml versus 5.3 ng/ml, P ≤ 0.001). Although IVM cycles yielded more cumulus-oocyte complexes (COCs) (24.5 versus 15.0 COC, P ≤ 0.001), both groups had similar numbers of mature oocytes (metaphase II (MII)) (11.9 MII versus 10.6 MII, P = 0.9). In the entire cohort, non-adjusted cumulative OPR from IVM was significantly lower (198/463, 42.8%) compared to OS (794/1244, 63.8%), P ≤ 0.001. When analysing OPR across different serum AMH strata, cumulative OPR in both groups converged with increasing serum AMH, and OPR from IVM was non-inferior compared to OS from serum AMH levels >10 ng/ml onwards (113/221, 51.1% (IVM); 29/48, 60.4% (OS)). The number of ETs needed to reach an ongoing pregnancy was comparable in both the IVM and the OS group (1.6 versus 1.5 ET's, P = 0.44). Multivariable regression analysis adjusting for ART type, age, BMI, oocyte number, and PCOS phenotype showed that the number of COCs was the only parameter associated with OPR in predicted hyperresponders with a serum AMH >10 ng/ml. LIMITATIONS, REASONS FOR CAUTION: These data should be interpreted with caution as the retrospective nature of the study holds the possibility of unmeasured confounding factors. WIDER IMPLICATIONS OF THE FINDINGS: Among subfertile women who are eligible for ART, IVM, and OS resulted in comparable reproductive outcomes in a subset of women with a serum AMH ≥10 ng/ml. These findings should be corroborated by a randomised controlled trial (RCT) comparing both treatments in selected patients with elevated AMH. STUDY FUNDING/COMPETING INTEREST(S): There was no external funding for this study. P.D. has been consultant to Merck Healthcare KGaA (Darmstadt, Germany) from April 2021 till June 2023 and is a Merck employee (Medical Director, Global Medical Affairs Fertility) with Merck Healthcare KGAaA (Darmstadt, Germany) since July 2023. He declares honoraria for lecturing from Merck KGaA, MSD, Organon, and Ferring. The remaining authors declared no conflict of interest pertaining to this study. TRIAL REGISTRATION NUMBER: N/A.

Does dual oocyte retrieval with continuous FSH administration increase the number of mature oocytes in low responders? An open-label randomized controlled trial.

STUDY QUESTION: Is there an increase in the total number of metaphase II (MII) oocytes between a conventional ovarian stimulation (OS) and a double uninterrupted stimulation? SUMMARY ANSWER: There is no increase in the total number of MII oocytes when comparing one conventional OS to a continuous stimulation with double oocyte aspiration. WHAT IS KNOWN ALREADY: Based on the concept of multiple follicular waves, the combination of two stimulations in the same ovarian cycle has gained interest in patients with a low ovarian reserve. This so-called dual stimulation approach is usually characterized by a discontinuation of FSH administration for ∼5 days and appears to have a favourable impact on the number of retrieved oocytes without affecting the embryo quality or ploidy status. The outcomes of dual uninterrupted OS have not yet been studied. STUDY DESIGN, SIZE, DURATION: This was an open-label randomized controlled trial (RCT) with superiority design, performed in a single tertiary centre. Subjects were randomized with a 1:1 allocation into two groups between October 2019 and September 2021. All patients underwent a conventional stimulation with recombinant FSH. When two or more follicles of 17 mm were present, the final inclusion criterion was assessed; randomization occurred only in the presence of ≤9 follicles of ≥11 mm. In Group A, ovulation was triggered with hCG, and oocyte retrieval (OR) was performed 34-36 h later, followed by a fresh single or double embryo transfer (SET or DET) on Day 3/5. In Group B, ovulation was triggered with GnRH agonist, followed by another OS, without discontinuation of the FSH administration. In the presence of one or more follicles of ≥17 mm, the second stimulation was completed with hCG. A freeze-all strategy (Day 3/5) was applied for both retrievals, followed by transfer of one or two embryos in an artificially prepared frozen-thawed cycle. In the absence of one or more follicles of ≥17 mm after 13 additional days of stimulation, the second cycle was cancelled. All ORs were executed by a senior fertility specialist who was blinded for the first treatment, and all follicles >10 mm were aspirated, according to routine clinical practice. The primary outcome was the total number of MII oocytes. Patients were followed up until all embryos were transferred, or until live birth was achieved. Other secondary outcomes included the number of cumulus-oocyte complexes (COCs), the number of good quality embryos (Day 3/5), the ongoing pregnancy rate, and gonadotropin consumption. PARTICIPANTS/MATERIALS, SETTING, METHODS: Patients between 25 and 40 years old, with an anti-Müllerian hormone level of ≤1.5 ng/ml, antral follicle count of ≤6, or ≤5 oocytes after a previous stimulation, were included. At the start, 70 patients were eligible for participation in the trial, of whom 48 patients fulfilled the final inclusion criterium and were randomized. After drop-out of two patients, 23 patients were randomized to a single round of OS (Group A), and 23 patients were randomized to two uninterrupted rounds of OS (Group B). MAIN RESULTS AND THE ROLE OF CHANCE: Baseline characteristics were similar between both groups. The cumulative number of COCs and MII oocytes after completion of the second OR was similar in Group A and Group B [5.3 ± 2.7 versus 5.3 ± 3.0 (P = 0.95); 4.1 ± 2.4 versus 4.3 ± 2.7 (P = 0.77)]. Likewise, a comparable number of excellent and good quality embryos was available on Day 3 (3.0 ± 2.0 versus 2.7 ± 2.0; P = 0.63). In Group B, the cancellation rate due to insufficient response to the second round of stimulation was 39.1% (9/23). When focusing on the first stimulation in both groups, there were no significant differences regarding basal FSH, gonadotropin consumption, and the number of preovulatory follicles. After the first OR, the mean number of COC and MII oocytes was significantly higher in Group A (who had hCG triggering), compared to Group B (who had GnRH agonist triggering) [5.3 ± 2.7 versus 3.3 ± 2.2; difference 95% CI (0.54 to 3.45), P = 0.004 and 4.1 ± 2.4 versus 3.0 ± 2.2; difference 95% CI (-0.15 to 2.6), P = 0.05, respectively]. Likewise, the number of excellent and good quality embryos on Day 3 was significantly higher (3.0 ± 2.0 versus 1.9 ± 1.7; P = 0.02) in Group A. LIMITATIONS, REASONS FOR CAUTION: This study was powered to demonstrate superiority for the number of MII oocytes after dual stimulation. Investigating the impact of dual stimulation on pregnancy rates would have required a larger sample size. Furthermore, the heterogeneity in embryo vitrification and transfer policies precluded a correct comparison of embryologic outcomes between both groups. WIDER IMPLICATIONS OF THE FINDINGS: This is the first RCT investigating the role of continuous stimulation with double aspiration in low responders. Our results show no statistically significant differences in the cumulative number of MII oocytes between one conventional stimulation with fresh ET and two consecutive stimulations with a freeze-only approach. Furthermore, the observed suboptimal oocyte yield after agonist ovulation triggering in low responders in the dual uninterrupted OS group is a reason for concern and further scrutiny, given that previous RCTs have shown similar outcomes in normal and high responders after hCG and GnRH agonist triggers. STUDY FUNDING/COMPETING INTEREST(S): This work was supported in part by a research grant from Organon. H.T. received honoraria for lectures and presentations from Abbott, Cooper Surgical, Gedeon-Richter, Cook, Goodlife, and Ferring. L.B. received fees for lectures from Merck & Organon and support for attending ESHRE 2023. M.D.V. reports fees for lectures from Ferring, Merck, Organon, IBSA, Gedeon Richter, and Cooper Surgical and support for attending ASRM 2023. S.M. received honoraria for lectures and presentations from Abbott, Cooper Surgical, Gedeon-Richter, IBSA, and Merck. C.B. was on the Advisory board and received consulting fees from Theramex and received honoraria for lectures and presentations from Abbott, Ferring, Gedeon-Richter, IBSA, and Merck. TRIAL REGISTRATION NUMBER: NCT03846544. TRIAL REGISTRATION DATE: 19 February 2019. DATE OF FIRST PATIENT'S ENROLMENT: 28 October 2019.

Oral dydrogesterone versus micronized vaginal progesterone for luteal phase support: a double-blind crossover study investigating pharmacokinetics and impact on the endometrium.

STUDY QUESTION: How do plasma progesterone (P) and dydrogesterone (D) concentrations together with endometrial histology, transcriptomic signatures, and immune cell composition differ when oral dydrogesterone (O-DYD) or micronized vaginal progesterone (MVP) is used for luteal phase support (LPS)? SUMMARY ANSWER: Although after O-DYD intake, even at steady-state, plasma D and 20αdihydrodydrogesterone (DHD) concentrations spiked in comparison to P concentrations, a similar endometrial signature was observed by histological and transcriptomic analysis of the endometrium. WHAT IS KNOWN ALREADY: O-DYD for LPS has been proven to be noninferior compared to MVP in two phase III randomized controlled trials. Additionally, a combined individual participant data and aggregate data meta-analysis indicated that a higher pregnancy rate and live birth rate may be obtained in women receiving O-DYD versus MVP for LPS in fresh IVF/ICSI cycles. Little data are available on the pharmacokinetic (PK) profiles of O-DYD versus MVP and their potential molecular differences at the level of the reproductive organs, particularly at the endometrial level. STUDY DESIGN, SIZE, DURATION: Thirty oocyte donors were planned to undergo two ovarian stimulation (OS) cycles with dual triggering (1.000 IU hCG + 0.2 mg triptorelin), each followed by 1 week of LPS: O-DYD or MVP, in a randomized, cross-over, double-blind, double-dummy fashion. On both the first and eighth days of LPS, serial blood samples upon first dosing were harvested for plasma D, DHD, and P concentration analyses. On Day 8 of LPS, an endometrial biopsy was collected for histologic examination, transcriptomics, and immune cell analysis. PARTICIPANTS/MATERIALS, SETTING, METHODS: All oocyte donors were <35 years old, had regular menstrual cycles, no intrauterine contraceptive device, anti-Müllerian hormone within normal range and a BMI ≤29 kg/m2. OS was performed on a GnRH antagonist protocol followed by dual triggering (1.000 IU hCG + 0.2 mg triptorelin) as soon as ≥3 follicles of 20 mm were present. Following oocyte retrieval, subjects initiated LPS consisting of MVP 200 mg or O-DYD 10 mg, both three times daily. D, DHD, and P plasma levels were measured using liquid chromatography-tandem mass spectrometry. Histological assessment was carried out using the Noyes criteria. Endometrial RNA-sequencing was performed for individual biopsies and differential gene expression was analyzed. Endometrial single-cell suspensions were created followed by flow cytometry for immune cell typing. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 21 women completed the entire study protocol. Subjects and stimulation characteristics were found to be similar between groups. Following the first dose of O-DYD, the average observed maximal plasma concentrations (Cmax) for D and DHD were 2.9 and 77 ng/ml, respectively. The Cmax for D and DHD was reached after 1.5 and 1.6 h (=Tmax), respectively. On the eighth day of LPS, the first administration of that day gave rise to a Cmax of 3.6 and 88 ng/ml for D and DHD, respectively. For both, the observed Tmax was 1.5 h. Following the first dose of MVP, the Cmax for P was 16 ng/ml with a Tmax of 4.2 h. On the eighth day of LPS, the first administration of that day showed a Cmax for P of 21 ng/ml with a Tmax of 7.3 h. All 42 biopsies showed endometrium in the secretory phase. The mean cycle day was 23.9 (±1.2) in the O-DYD group versus 24.0 (±1.3) in the MVP group. RNA-sequencing did not reveal significantly differentially expressed genes between samples of both study groups. The average Euclidean distance between samples following O-DYD was significantly lower than following MVP (respectively 12.1 versus 18.8, Mann-Whitney P = 6.98e-14). Immune cell profiling showed a decrease of CD3 T-cell, γδ T-cell, and B-cell frequencies after MVP treatment compared to O-DYD, while the frequency of natural killer (NK) cells was significantly increased. LIMITATIONS, REASONS FOR CAUTION: The main reason for caution is the small sample size, given the basic research nature of the project. The plasma concentrations are best estimates as this was not a formal PK study. Whole tissue bulk RNA-sequencing has been performed not correcting for bias caused by different tissue compositions across biopsies. WIDER IMPLICATIONS OF THE FINDINGS: This is the first study comparing O-DYD/MVP, head-to-head, in a randomized design on a molecular level in IVF/ICSI. Plasma serum concentrations suggest that administration frequency is important, in addition to dose, specifically for O-DYD showing a rapid clearance. The molecular endometrial data are overall comparable and thus support the previously reported noninferior reproductive outcomes for O-DYD as compared to MVP. Further research is needed to explore the smaller intersample distance following O-DYD and the subtle changes detected in endometrial immune cells. STUDY FUNDING/COMPETING INTEREST(S): Not related to this work, C.Bl. has received honoraria for lectures, presentations, manuscript writing, educational events, or scientific advice from Abbott, Ferring, Organon, Cooper Surgical, Gedeon-Richter, IBSA, and Merck. H.T. has received honoraria for lectures, presentations, manuscript writing, educational events, or scientific advice from Abbott, Ferring, Cooper Surgical, Gedeon-Richter, Cook, and Goodlife. S.M. has received honoraria for lectures, presentations, educational events, or scientific advice from Abbott, Cooper Surgical, Gedeon-Richter, IBSA, and Merck and Oxolife. G.G. has received honoraria for lectures, presentations, educational events, or scientific advice from Merck, MSD, Organon, Ferring, Theramex, Gedeon-Richter, Abbott, Biosilu, ReprodWissen, Obseva, PregLem, Guerbet, Cooper, Igyxos, and OxoLife. S.V.-S. is listed as inventor on two patents (WO2019115755A1 and WO2022073973A1), which are not related to this work. TRIAL REGISTRATION NUMBER: EUDRACT 2018-000105-23.

Does the dose or type of gonadotropins affect the reproductive outcomes of poor responders undergoing modified natural cycle IVF (MNC-IVF)?

OBJECTIVE: Does the dose or type of gonadotropin affect the reproductive outcomes of poor responders undergoing IVF in a modified natural cycle (MNC-IVF)? STUDY DESIGN: This is a retrospective cohort study including patients attending a tertiary referral University Hospital from 1st January 2017 until 1st March 2020. All predicted poor responders (Poseidon groups 3 and 4) who underwent MNC-IVF in our center were included. Mild ovarian stimulation (rFSH/uFSH/hp-hMG) was started when a follicle with a mean diameter of 12-14 mm was observed on ultrasound scan; GnRH antagonist was added from the next day onwards. Mature oocytes were inseminated using ICSI. RESULTS: In total 484 patients undergoing 1398 cycles were included. Mean (SD) age and serum AMH were 38.2 (3.7) years and 0.28 (0.26) ng/ml, respectively. The daily dose of gonadotropins was either < 75 IU/d [11/1398 (0.8 %)] or 75 to < 100 IU/d [1303/1398 (93.2 %)] or ≥ 100 to 150 IU/d [84/1398 (6 %)]. Patients were stimulated with rFSH [251/1398 (18 %)], uFSH [45/1398 (3.2 %)] or hp-hMG [1102/1398 (78.8 %)]. Clinical pregnancy rate was 119/1398 (8.5 %). Live birth was achieved in 80/1398 (5.7 %) of cycles. There was no significant difference in rates of pregnancy and live birth across different types and doses of gonadotropins. The GEE multivariate regression analysis, adjusting for relevant confounders, showed that the type of treatment strategy (rFSH/uFSH/hp-hMG) and the daily dose of gonadotropins were not associated with live birth rates (LBR) (p value 0.08 and 0.8, respectively). CONCLUSIONS: The type and daily dose of gonadotropins do not affect the reproductive outcome of poor responders undergoing MNC-IVF.

Impact of cell loss after warming of human vitrified day 3 embryos on obstetric outcome in single frozen embryo transfers.

PURPOSE: Does cell loss (CL) after vitrification and warming (V/W) of day 3 embryos have an impact on live birth rate (LBR) and neonatal outcomes? METHOD: This retrospective analysis includes cleavage stage day 3 embryos vitrified/warmed between 2011 and 2018. Only single vitrified/warmed embryo transfers were included. Pre-implantation genetic screening, oocyte donation, and age banking were excluded from the analysis. The sample was divided into two groups: group A (intact embryo after warming) and group B (≤ 50% blastomere loss after warming). RESULTS: On the total embryos (n = 2327), 1953 were fully intact (83.9%, group A) and 374 presented cell damage (16.1%, group B). In group B, 62% (232/374) of the embryos had lost only one cell. Age at cryopreservation, cause of infertility, insemination procedure, and semen origin were comparable between the two groups. The positive hCG rate (30% and 24.3%, respectively, for intact vs CL group, p = 0.028) and LBR (13.7% and 9.4%, respectively, for intact vs CL group, p = 0.023) per warming cycle were significantly higher for intact embryos. However, LBR per positive hCG was equivalent between intact and damaged embryos (45.6% vs 38.5%, respectively, p = 0.2). Newborn measurements (length, weight, and head circumference at birth) were comparable between the two groups. Multivariate logistic regression showed that the presence of CL is not predictive for LB when adjusting for patients' age. CONCLUSIONS: LBR is significantly higher after transfer of an intact embryo compared to an embryo with CL after warming; however, neonatal outcomes are comparable between the two groups.

Early pregnancy loss in patients with polycystic ovary syndrome after IVM versus standard ovarian stimulation for IVF/ICSI.

STUDY QUESTION: Is the incidence of early pregnancy loss (EPL) in patients with polycystic ovary syndrome (PCOS) higher after IVM of oocytes than after ovarian stimulation (OS) for IVF/ICSI? SUMMARY ANSWER: Women with PCOS who are pregnant after fresh embryo transfer have a higher probability of EPL following IVM, but after frozen embryo transfer (FET), no significant difference in the incidence of EPL was observed following IVM compared to OS. WHAT IS KNOWN ALREADY: There is conflicting evidence in the current literature with regard to the risk of EPL after IVM of oocytes when compared with OS. Because of the limited sample size in previous studies, the use of different IVM systems and the possible bias introduced by patient characteristics and treatment type, firm conclusions cannot be drawn. STUDY DESIGN, SIZE, DURATION: This was a retrospective cohort study evaluating 800 women, with a diagnosis of infertility and PCOS as defined by Rotterdam criteria, who had a first positive pregnancy test after fresh or FET following IVM or OS between January 2010 and December 2017 in a tertiary care academic medical centre. PARTICIPANTS/MATERIALS, SETTING, METHODS: Pregnancies after non-hCG triggered IVM following a short course of highly purified human menopausal gonadotropin were compared with those after conventional OS. The primary outcome was EPL, defined as a spontaneous pregnancy loss before 10 weeks of gestation. MAIN RESULTS AND THE ROLE OF CHANCE: In total, 329 patients with a positive pregnancy test after IVM and 471 patients with a positive pregnancy test after OS were included. Women who were pregnant after IVM were younger (28.6 ± 3.4 years vs 29.3 ± 3.6 years, P = 0.005) and had higher serum anti-Mullerian hormone levels (11.5 ± 8.1 ng/ml vs 7.2 ± 4.1 ng/ml, P < 0.001) compared to those who were pregnant after OS. The distribution of PCOS phenotypes was significantly different among women in the IVM group compared to those in the OS group and women who were pregnant after OS had previously suffered EPL more often (28% vs 17.6%, P = 0.003). EPL was significantly higher after fresh embryo transfer following IVM compared to OS (57/122 (46.7%) vs 53/305 (17.4%), P < 0.001), while the results were comparable after FET (63/207 (30.4%) vs 60/166 (36.1%), respectively, P = 0.24). In the multivariate logistic regression analysis evaluating fresh embryo transfer cycles, IVM was the only independent factor (adjusted odds ratio (aOR) 4.24, 95% CI 2.44-7.37, P < 0.001)) significantly associated with increased odds of EPL. On the other hand, when the same model was applied to FET cycles, the type of treatment (IVM vs OS) was not significantly associated with EPL (aOR 0.73, 95% CI 0.43-1.25, P = 0.25). LIMITATIONS, REASONS FOR CAUTION: The current data are limited by the retrospective nature of the study and the potential of bias due to unmeasured confounders. WIDER IMPLICATIONS OF THE FINDINGS: The increased risk of EPL after fresh embryo transfer following IVM may point towards inadequate endometrial development in IVM cycles. Adopting a freeze-all strategy after IVM seems more appropriate. Future studies are needed to ascertain the underlying cause of this observation. STUDY FUNDING/COMPETING INTEREST(S): The Clinical IVM research has been supported by research grants from Cook Medical and Besins Healthcare. All authors declared no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

To trigger or not to trigger ovulation in a natural cycle for frozen embryo transfer: a randomized controlled trial.

STUDY QUESTION: Is the clinical pregnancy rate (CPR) following a frozen embryo transfer (FET) in a natural cycle (NC) higher after spontaneous ovulation than after triggered ovulation [natural cycle frozen embryo transfer (NC-FET) versus modified NC-FET]? SUMMARY ANSWER: The CPR did not vary significantly between the two FET preparation protocols. WHAT IS KNOWN ALREADY: Although the use of FET is continuously increasing, the most optimal endometrial preparation protocol is still under debate. For transfer in the NC specifically, conflicting results have been reported in terms of the outcome following spontaneous or triggered ovulation. STUDY DESIGN, SIZE, DURATION: In a tertiary hospital setting, subjects were randomized with a 1:1 allocation into two groups between January 2014 and January 2019. Patients in group A underwent an NC-FET, while in group B, a modified NC-FET was performed with a subcutaneous hCG injection to trigger ovulation. In neither group was additional luteal phase support administered. All embryos were vitrified-warmed on Day 3 and transferred on Day 4 of embryonic development. The primary outcome was CPR at 7 weeks. All patients were followed further until 10 weeks of gestation when the ongoing pregnancy rate (OPR) was defined by the observation of foetal cardiac activity on ultrasound scan. Other secondary outcomes included biochemical pregnancy rate, early pregnancy loss and the number of visits, blood samples and ultrasonographic examinations prior to FET. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 260 patients (130 per study arm) were randomized, of whom 12 withdrew consent after study arm allocation. A total of 3 women conceived spontaneously before initiating the study cycle and 16 did not start for personal or medical reasons. Of the 229 actually commencing monitoring for the study FET cycle, 7 patients needed to be switched to a hormonal replacement treatment protocol due to the absence of follicular development, 12 had no embryo available for transfer after warming and 37 had a spontaneous LH surge before the ovulation trigger could be administered, although they were allocated to group B. Given the above, an intention-to-treat (ITT) analysis was performed taking into account 248 patients (125 in group A and 123 in group B), as well as a per protocol (PP) analysis on a subset of 173 patients (110 in group A and 63 in group B). MAIN RESULTS AND THE ROLE OF CHANCE: Demographic features were evenly distributed between the study groups, as were the relevant fresh and frozen ET cycle characteristics. According to the ITT analysis, the CPR and OPR in group A (33.6% and 27.2%, respectively) and group B (29.3% and 24.4%, respectively) did not vary significantly [relative risk (RR) 0.87, 95% CI (0.60;1.26), P = 0.46 and RR 0.90, 95% CI (0.59;1.37), P = 0.61, respectively]. Biochemical pregnancy rate and early pregnancy loss were also found to be not statistically significantly different between the groups. In contrast, more clinic visits and blood samplings for cycle monitoring were required in the NC-FET group (4.05 ± 1.39) compared with the modified NC-FET group (3.03 ± 1.16, P = <0.001), while the number of ultrasound scans performed were comparable (1.70 ± 0.88 in group A versus 1.62 ± 1.04 in group B). The additional PP analysis was in line with the ITT results: CPR in group A was 36.4% versus 38.1% in group B [RR 1.05, 95% CI (0.70;1.56), P = 0.82]. LIMITATIONS, REASONS FOR CAUTION: The results are limited by the high drop-out rate for the PP analysis in the modified NC-FET group as more than one-third of the subjects allocated to this group ovulated spontaneously before ovulation triggering. Nonetheless, this issue is inherent to routine clinical practice and is an important observation of an event that can only be avoided by performing a very extensive monitoring that limits the practical advantages associated with modified NC-FET. Furthermore, although this is the largest randomized controlled trial (RCT) investigating this specific research question so far, a higher sample size would allow smaller differences in clinical outcome to be detected, since currently they may be left undetected. WIDER IMPLICATIONS OF THE FINDINGS: This RCT adds new high-quality evidence to the existing controversial literature concerning the performance of NC-FET versus modified NC-FET. Based on our results showing no statistically significant differences in clinical outcomes between the protocols, the treatment choice may be made according to the patient's and treating physician's preferences. However, the modified NC-FET strategy reduces the need for hormonal monitoring and may therefore be considered a more patient-friendly and potentially cost-effective approach. STUDY FUNDING/COMPETING INTEREST(S): No specific funding was available for this study. None of the authors have a conflict of interest to declare with regard to this study. TRIAL REGISTRATION NUMBER: NCT02145819. TRIAL REGISTRATION DATE: 8 January 2014. DATE OF FIRST PATIENT'S ENROLMENT: 21 January 2014.

Follicular-phase endometrial scratching: a truncated randomized controlled trial.

STUDY QUESTION: Does intentional endometrial injury (scratching) during the follicular phase of ovarian stimulation (OS) increase the clinical pregnancy rate (CPR) in ART? SUMMARY ANSWER: CPR did not vary between the endometrial injury and the control group, but the trial was underpowered due to early termination because of a higher clinical miscarriage rate observed in the endometrial injury arm after a prespecified interim analysis. WHAT IS KNOWN ALREADY: Intentional endometrial injury has been put forward as an inexpensive clinical tool capable of enhancing endometrial receptivity. However, despite its widespread use, the benefit of endometrial scratching remains controversial, with several recent randomized controlled trials (RCTs) being unable to confirm its added value. So far, most research has focused on endometrial scratching during the luteal phase of the cycle preceding the one with embryo transfer (ET), while only a few studies investigated in-cycle injury during the follicular phase of OS. Also, the persistence of a scratch effect in subsequent treatment cycles remains unclear and possible harms have been insufficiently studied. STUDY DESIGN, SIZE, DURATION: This RCT was performed in a tertiary hospital setting between 3 April 2014 and 8 October 2017. A total of 200 women (100 per study arm) undergoing IVF/ICSI in a GnRH antagonist suppressed cycle followed by fresh ET were included. PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants were randomized with a 1:1 allocation ratio to either undergo a pipelle endometrial biopsy between Days 6 and 8 of OS or to be in the control group.The primary outcome was CPR. Secondary outcomes included biochemical pregnancy rate, live birth rate (LBR), early pregnancy loss (biochemical pregnancy losses and clinical miscarriages), excessive procedure pain/bleeding and cumulative reproductive outcomes within 6 months of the study cycle. MAIN RESULTS AND THE ROLE OF CHANCE: The RCT was stopped prematurely by the trial team after the second prespecified interim analysis raised safety concerns, namely a higher clinical miscarriage rate in the intervention group. The intention-to-treat CPR was similar between the biopsy and the control arm (respectively, 44 versus 40%, P = 0.61, risk difference = 3.6 with 95% confidence interval = -10.1;17.3), as was the LBR (respectively, 32 versus 36%, P = 0.52). The incidence of a biochemical pregnancy loss was comparable between both groups (10% in the intervention group versus 15% in the control, P = 0.49), but clinical miscarriages occurred significantly more frequent in the biopsy group (25% versus 8%, P = 0.032). In the intervention group, 3% of the patients experienced excessive procedure pain and 5% bleeding. The cumulative LBR taking into account all conceptions (spontaneous or following ART) within 6 months of randomization was not significantly different between the biopsy and the control group (54% versus 60%, respectively, P = 0.43). LIMITATIONS, REASONS FOR CAUTION: The trial was stopped prematurely due to safety concerns after the inclusion of 200 of the required 360 patients. Not reaching the predefined sample size implies that definite conclusions on the outcome parameters cannot be drawn. Furthermore, the pragmatic design of the study may have limited the detection of specific subgroups of women who may benefit from endometrial scratching. WIDER IMPLICATIONS OF THE FINDINGS: Intentional endometrial injury during the follicular phase of OS warrants further attention in future research, as it may be harmful. These findings should be taken in consideration together with the growing evidence from other RCTs that scratching may not be beneficial. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by 'Fonds Wetenschappelijk Onderzoek' (FWO, Flanders, Belgium, 11M9415N, 1524417N). None of the authors have a conflict of interest to declare with regard to this study.

Do we need to measure progesterone in oocyte donation cycles? A retrospective analysis evaluating cumulative live birth rates and embryo quality.

STUDY QUESTION: Does late follicular-phase elevated serum progesterone (LFEP) during ovarian stimulation for oocyte donation have an impact on embryo quality (EQ) and cumulative live birth rate (CLBR)? SUMMARY ANSWER: LFEP does not have an influence on EQ nor CLBR in oocyte donation cycles. WHAT IS KNOWN ALREADY: Ovarian stimulation promotes the production of progesterone (P) which, when elevated during the follicular phase, has been demonstrated to have a deleterious effect in autologous fresh IVF outcomes. While there is robust evidence that this elevation results in impaired endometrial receptivity, the impact on EQ remains a matter of debate. The oocyte donation model is an excellent tool to assess the effects of LFEP on EQ from those on endometrium receptivity separately. Previous studies in oocyte donation cycles investigating the influence of elevated P on pregnancy outcomes in oocyte recipients showed conflicting results. STUDY DESIGN, SIZE, DURATION: This is a retrospective analysis including all GnRH antagonist down-regulated cycles for fresh oocyte donation taking place in a tertiary referral university hospital between 2010 and 2017. A total of 397 fresh donor-recipient cycles were included. Each donor was included only once in the analysis and could be associated to a single recipient. PARTICIPANTS/MATERIALS, SETTING, METHODS: The sample was stratified according to serum P levels of ≤1.5 and >1.5 ng/mL on the day of ovulation triggering. The primary endpoint of the study was the top-quality embryo rate on Day 3, and the secondary outcome measure was CLBR defined as a live-born delivery beyond 24 weeks. MAIN RESULTS AND THE ROLE OF CHANCE: Three hundred ninety-seven fresh oocyte donation cycles were included in the analysis, of which 314 (79%) had a serum P ≤ 1.5 ng/mL and 83 (20.9%) had a serum P > 1.5 ng/mL. The average age of the oocyte donors was 31.4 ± 4.7 and 29.9 ± 4.5 years, respectively, for normal and elevated P (P = 0.017). The mean number of oocytes retrieved was significantly higher in the elevated P group with 16.6 ± 10.6 vs 11.5 ± 6.9 in the P ≤ 1.5 group (P < 0.001).In parallel, the total number of embryos on Day 3, as well as the number of good-quality embryos at this stage, was significantly higher in the elevated P group (6.6 ± 5.6 vs 4.15 ± 3.5 and 8.7 ± 6.3 vs 6.1 ± 4.4; respectively, P < 0.001). However, maturation and fertilization rates did not vary significantly between the two study groups and neither did the top- and good-quality embryo rate and the embryo utilization rate, all evaluated on Day 3 (P = 0.384, P = 0.405 and P = 0.645, respectively). A multivariable regression analysis accounting for P groups, age of the donor, number of retrieved oocytes and top-quality embryo rate as potential confounders showed that LFEP negatively influenced neither the top-quality embryo rate nor the CLBR. LIMITATIONS, REASONS FOR CAUTION: This is an observational study based on a retrospective data analysis. Better extrapolation of the results could be validated by performing a prospective trial. Furthermore, this study was focused on oocyte donation cycles and hence the results cannot be generalized to the entire infertile population. WIDER IMPLICATIONS OF THE FINDINGS: This is the first study providing evidence that LFEP does not influence CLBR and is adding strong evidence to the existing literature that LFEP does not harm EQ in oocyte donation programs. STUDY FUNDING/COMPETING INTERESTS: Not applicable.

The proliferative phase endometrium in IVF/ICSI: an in-cycle molecular analysis predictive of the outcome following fresh embryo transfer.

STUDY QUESTION: Does an early proliferative phase endometrial biopsy harvested during ovarian stimulation harbour information predictive of the outcome following fresh embryo transfer (ET) in that same cycle? SUMMARY ANSWER: Transcriptome analysis of the whole-tissue endometrium did not reveal significant differential gene expression (DGE) in relation to the outcome; however, the secretome profile of isolated, cultured and in vitro decidualized endometrial stromal cells (EnSCs) varied significantly between patients who had a live birth compared to those with an implantation failure following fresh ET in the same cycle as the biopsy. WHAT IS KNOWN ALREADY: In the majority of endometrial receptivity research protocols, biopsies are harvested during the window of implantation (WOI). This, however, precludes ET in that same cycle, which is preferable as the endometrium has been shown to adapt over time. Endometrial biopsies taken during ovarian stimulation have been reported not to harm the chances of implantation, and in such biopsies DGE has been observed between women who achieve pregnancy versus those who do not. The impact of the endometrial proliferative phase on human embryo implantation remains unclear, but deserves further attention, especially since in luteal phase endometrial biopsies, a transcriptional signature predictive for repeated implantation failure has been associated with reduced cell proliferation, possibly indicating proliferative phase involvement. Isolation, culture and in vitro decidualization (IVD) of EnSCs is a frequently applied basic research technique to assess endometrial functioning, and a disordered EnSC secretome has previously been linked with failed implantation. STUDY DESIGN, SIZE, DURATION: This study was nested in a randomized controlled trial (RCT) investigating the effect of endometrial scratching during the early follicular phase of ovarian stimulation on clinical pregnancy rates after IVF/ICSI. Of the 96 endometrial biopsies available, after eliminating those without fresh ET and after extensive matching in order to minimize the risk of potential confounding, 18 samples were retained to study two clinical groups: nine biopsies of patients with a live birth versus nine biopsies of patients with an implantation failure, both following fresh ET performed in the same cycle as the biopsy. We studied the proliferative endometrium by analysing its transcriptome and by isolating, culturing and decidualizing EnSCs in vitro. We applied this latter technique for the first time on proliferative endometrial biopsies obtained during ovarian stimulation for in-cycle outcome prediction, in an attempt to overcome inter-cycle variability. PARTICIPANTS/MATERIALS, SETTING, METHODS: RNA-sequencing was performed for 18 individual whole-tissue endometrial biopsies on an Illumina HiSeq1500 machine. DGE was analysed three times using different approaches (DESeq2, EdgeR and the Wilcoxon rank-sum test, all in R). EnSC isolation and IVD was performed (for 2 and 4 days) for a subset of nine samples, after which media from undifferentiated and decidualized cultures were harvested, stored at -80°C and later assayed for 45 cytokines using a multiplex suspension bead immunoassay. The analysis was performed by partial least squares regression modelling. MAIN RESULTS AND THE ROLE OF CHANCE: After correction for multiple hypothesis testing, DGE analysis revealed no significant differences between endometrial samples from patients who had a live birth and those with an implantation failure following fresh ET. However secretome analysis after EnSC isolation and culture, showed two distinct clusters that clearly corresponded to the two clinical groups. Upon IVD, the secretome profiles shifted from that of undifferentiated cells but the difference between the two clinical groups remained yet were muted, suggesting convergence of cytokine profiles after decidualization. LIMITATIONS, REASONS FOR CAUTION: Caution is warranted due to the limited sample size of the study and the in vitro nature of the EnSC experiment. Validation on a larger scale is necessary, however, hard to fulfil given the very limited availability of in-cycle proliferative endometrial biopsies outside a RCT setting. WIDER IMPLICATIONS OF THE FINDINGS: These data support the hypothesis that the endometrium should be assessed not only during the WOI and that certain endometrial dysfunctionalities can probably be detected early in a cycle by making use of the proliferative phase. This insight opens new horizons for the development of endometrial tests, whether diagnostic or predictive of IVF/ICSI treatment outcome. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by Fonds Wetenschappelijk Onderzoek (FWO, Flanders, Belgium, 11M9415N, 1 524 417N), Wetenschappelijk Fonds Willy Gepts (WFWG G160, Universitair Ziekenhuis Brussel, Belgium) and the National Medicine Research Council (NMRC/CG/M003/2017, Singapore). There are no conflicts of interests. TRIAL REGISTRATION NUMBER: NCT02061228.

Predicting suboptimal oocyte yield following GnRH agonist trigger by measuring serum LH at the start of ovarian stimulation.

STUDY QUESTION: Are the LH levels at the start of ovarian stimulation predictive of suboptimal oocyte yield from GnRH agonist triggering in GnRH antagonist down-regulated cycles? SUMMARY ANSWER: LH levels at the start of ovarian stimulation are an independent predictor of suboptimal oocyte yield following a GnRH agonist trigger. WHAT IS KNOWN ALREADY: A GnRH agonist ovulation trigger may result in an inadequate oocyte yield in a small subset of patients. This failure can range from empty follicle syndrome to the retrieval of much fewer oocytes than expected. Suboptimal response to a GnRH agonist trigger has been defined as the presence of circulating LH levels <15 IU/l 12 h after triggering. It has been shown that patients with immeasurable LH levels on trigger day have an up to 25% risk of suboptimal response. STUDY DESIGN, SIZE, DURATION: In this retrospective cohort study, all patients (n = 3334) who received GnRH agonist triggering (using Triptoreline 0.2 mg) for final oocyte maturation undergoing a GnRH antagonist cycle in our centre from 2011 to 2017 were included. The primary outcome of the study was oocyte yield, defined as the ratio between the total number of collected oocytes and the number of follicles with a mean diameter >10 mm prior to GnRH agonist trigger. PARTICIPANTS/MATERIALS, SETTING, METHODS: The endocrine profile of all patients was studied at initiation as well as at the end of ovarian stimulation. In order to evaluate whether LH levels, not only at the end but also at the start, of ovarian stimulation predicted oocyte yield, we performed multivariable regression analysis adjusting for the following confounding factors: female age, body mass index, oral contraceptives before treatment, basal and trigger day estradiol levels, starting FSH levels, use of highly purified human menopausal gonadotrophin and total gonadotropin dose. Suboptimal response to GnRH agonist trigger was defined as <10th percentile of oocyte yield. MAIN RESULTS AND THE ROLE OF CHANCE: The average age was 31.9 years, and the mean oocyte yield was 89%. The suboptimal response to GnRH agonist trigger cut-off (<10th percentile) was 45%, which was exhibited by 340 patients. Following confounder adjustment, multivariable regression analysis showed that LH levels at the initiation of ovarian stimulation remained an independent predictor of suboptimal response even in the multivariable model (adjusted OR 0.920, 95% CI 0.871-0.971). Patients with immeasurable LH levels at the start of stimulation (<0.1 IU/l) had a 45.2% risk of suboptimal response, while the risk decreased with increasing basal LH levels; baseline circulating LH <0.5 IU/L, <2 IU/L and <5 IU/L were associated with a 39.1%, 25.2% and 13.6% risk, respectively. LIMITATIONS, REASONS FOR CAUTION: The main limitation of the study is its retrospective design. WIDER IMPLICATIONS OF THE FINDINGS: This is the largest study of GnRH agonist trigger cycles only, since most of the previous research on the predictive value of basal LH levels was performed in dual trigger cycles. LH values should be measured prior to start of ovarian stimulation. In cases where they are immeasurable, suboptimal response to GnRH agonist trigger can be anticipated, and an individualized approach is warranted. STUDY FUNDING/COMPETING INTEREST(S): There was no funding and no competing interests. TRIAL REGISTRATION NUMBER: Not applicable.

Expression of adhesion and extracellular matrix genes in human blastocysts upon attachment in a 2D co-culture system.

STUDY QUESTION: What are the changes in human embryos, in terms of morphology and gene expression, upon attachment to endometrial epithelial cells? SUMMARY ANSWER: Apposition and adhesion of human blastocysts to endometrial epithelial cells are predominantly initiated at the embryonic pole and these steps are associated with changes in expression of adhesion and extracellular matrix (ECM) genes in the embryo. WHAT IS KNOWN ALREADY: Both human and murine embryos have been co-cultured with Ishikawa cells, although embryonic gene expression associated with attachment has not yet been investigated in an in vitro implantation model. STUDY DESIGN, SIZE, DURATION: Vitrified human blastocysts were warmed and co-cultured for up to 48 h with Ishikawa cells, a model cell line for receptive endometrial epithelium. PARTICIPANTS/MATERIALS, SETTING, METHODS: Six days post-fertilization (6dpf) human embryos were co-cultured with Ishikawa cells for 12, 24 (7dpf) or 48 h (8dpf) and attachment rate and morphological development investigated. Expression of 84 adhesion and ECM genes was analysed by quantitative PCR. Immunofluorescence microscopy was used to assess the expression of three informative genes at the protein level. Data are reported on 145 human embryos. Mann-Whitney U was used for statistical analysis between two groups, with P < 0.05 considered significant. MAIN RESULTS AND THE ROLE OF CHANCE: The majority of embryos attached to Ishikawa cells at the level of the polar trophectoderm; 41% of co-cultured embryos were loosely attached after 12 h and 86% firmly attached after 24 h. Outgrowth of hCG-positive embryonic cells at 8dpf indicated differentiation of trophectoderm into invasive syncytiotrophoblast. Gene expression analysis was performed on loosely attached and unattached embryos co-cultured with Ishikawa cells for 12 h. In contrast to unattached embryos, loosely attached embryos expressed THBS1, TNC, COL12A1, CTNND2, ITGA3, ITGAV and LAMA3 and had significantly higher CD44 and TIMP1 transcript levels (P = 0.014 and P = 0.029, respectively). LAMA3, THBS1 and TNC expressions were validated at the protein level in firmly attached 7dpf embryos. Thrombospondin 1 (THBS1) resided in the cytoplasm of embryonic cells whereas laminin subunit alpha 3 (LAMA3) and tenascin C (TNC) were expressed on the cell surface of trophectoderm cells. Incubation with a neutralizing TNC antibody did not affect the rate of embryo attachment or hCG secretion. LARGE SCALE DATA: None. LIMITATIONS, REASONS FOR CAUTION: This in vitro study made use of an endometrial adenocarcinoma cell line to mimic receptive luminal epithelium. Also, the number of embryos was limited. Contamination of recovered embryos with Ishikawa cells was unlikely based on their differential gene expression profiles. WIDER IMPLICATIONS OF THE FINDINGS: Taken together, we provide a 'proof of concept' that initiation of the implantation process coincides with the induction of specific embryonic genes. Genome-wide expression profiling of a larger sample set may provide insights into the molecular embryonic pathways underlying successful or failed implantation. STUDY FUNDING AND COMPETING INTEREST(S): A.A. was supported by a grant from the 'Instituut voor Innovatie door Wetenschap en Technologie' (IWT, 121716, Flanders, Belgium). This work was supported by the 'Wetenschappelijk Fonds Willy Gepts' (WFWG G142 and G170, Universitair Ziekenhuis Brussel). The authors declare no conflict of interest.

Impact of late-follicular phase elevated serum progesterone on cumulative live birth rates: is there a deleterious effect on embryo quality?

STUDY QUESTION: Is elevated late-follicular phase progesterone (EP) associated with a deleterious impact on embryo quality (EQ) and cumulative live birth rates (LBRs)? SUMMARY ANSWER: EP was associated with a decrease in embryo utilization and cumulative LBRs. WHAT IS KNOWN ALREADY: Ovarian stimulation promotes the production of progesterone (P) which adversely affects IVF pregnancy outcomes. However, evidence regarding a potential association between EP an EQ is lacking. STUDY DESIGN, SIZE, DURATION: A retrospective analysis of all GnRH antagonist down-regulated ICSI cycles followed by a fresh embryo transfer (ET) between 2010 and 2015 was performed. The sample was stratified according to the following P levels on the day of ovulation triggering: ≤0.50, 0.51-1.49 and ≥1.50 ng/ml. The primary outcomes were embryo utilization rates (number of embryos transferred or cryopreserved) and cumulative LBR, defined as the occurrence of the first live-birth after either the fresh or one of the subsequent frozen ET. PARTICIPANTS/MATERIALS, SETTING, METHODS: Overall, 3400 cycles were included in the analysis, using multivariable regression to account for potential confounding. MAIN RESULTS AND THE ROLE OF CHANCE: Female age and the number of oocytes retrieved increased significantly with increasing serum P values. Utilization rates decreased linearly as P increased for Day 3 embryos (72.3, 63.0 and 45.4%, respectively), while for Day 5 embryos only the EP group was associated with a significant decrease (48.8, 47.8 and 38.8%, respectively). EP was also associated with decreased fresh and cumulative LBRs. LIMITATIONS REASONS FOR CAUTION: The main limitations of this study were its retrospective nature and the fact that it was restricted to GnRH antagonist cycles. WIDER IMPLICATIONS OF THE FINDINGS: These results raise the question whether EP may also be associated with a decrease in cumulative pregnancy outcomes by increasing embryo wastage. Further studies may evaluate the potential benefit of additional measures besides the freeze-all strategy to avoid this issue, such as lowering the stimulation dose or applying a step-down protocol. STUDY FUNDING/COMPETING INTEREST(S): None.

Frozen embryo transfer: a review on the optimal endometrial preparation and timing.

STUDY QUESTION: What is the optimal endometrial preparation protocol for a frozen embryo transfer (FET)? SUMMARY ANSWER: Although the optimal endometrial preparation protocol for FET needs further research and is yet to be determined, we propose a standardized timing strategy based on the current available evidence which could assist in the harmonization and comparability of clinic practice and future trials. WHAT IS KNOWN ALREADY: Amid a continuous increase in the number of FET cycles, determining the optimal endometrial preparation protocol has become paramount to maximize ART success. In current daily practice, different FET preparation methods and timing strategies are used. STUDY DESIGN, SIZE, DURATION: This is a review of the current literature on FET preparation methods, with special attention to the timing of the embryo transfer. PARTICIPANTS/MATERIALS, SETTING, METHODS: Literature on the topic was retrieved in PubMed and references from relevant articles were investigated until June 2017. MAIN RESULTS AND THE ROLE OF CHANCE: The number of high quality randomized controlled trials (RCTs) is scarce and, hence, the evidence for the best protocol for FET is poor. Future research should compare both the pregnancy and neonatal outcomes between HRT and true natural cycle (NC) FET. In terms of embryo transfer timing, we propose to start progesterone intake on the theoretical day of oocyte retrieval in HRT and to perform blastocyst transfer at hCG + 7 or LH + 6 in modified or true NC, respectively. LIMITATIONS REASONS FOR CAUTION: As only a few high quality RCTs on the optimal preparation for FET are available in the existing literature, no definitive conclusion for benefit of one protocol over the other can be drawn so far. WIDER IMPLICATIONS OF THE FINDINGS: Caution when using HRT for FET is warranted since the rate of early pregnancy loss is alarmingly high in some reports. STUDY FUNDING/COMPETING INTEREST(S): S.M. is funded by the Research Fund of Flanders (FWO). H.T. and C.B. report grants from Merck, Goodlife, Besins and Abbott during the conduct of the study. TRIAL REGISTRATION NUMBER: Not applicable.

Vitrified-warmed blastocyst transfer on the 5th or 7th day of progesterone supplementation in an artificial cycle: a randomised controlled trial.

Prospective studies comparing different durations of progesterone supplementation before transfer of vitrified-warmed blastocysts in an artificial cycle are lacking. However, in oocyte donation programmes, the sporadic available evidence demonstrates considerable differences in clinical pregnancy rates according to the duration of progesterone administration. This randomised controlled trial (RCT), included 303 patients undergoing a frozen-thawed embryo transfer (FET) of one or two vitrified-warmed blastocyst(s) in an artificial cycle. Randomisation was performed when the endometrial thickness reached ≥7 mm after oestrogen supplementation. One hundred and fifty two patients in group A received 7 d of vaginal micronised progesterone tablets and 151 patients in group B received 5 d of micronised vaginal progesterone before FET. No differences were seen in clinical pregnancy rate between both groups: 42/152 (27.6%) in group A versus 49/151 (32.5%) in group B. Although no statistically significant difference was observed in clinical pregnancy rates, our study was powered to detect an absolute difference of 16%. In this regard, we cannot exclude that smaller, clinically relevant differences might exist and our study did not have the power to detect this. Patients were also not blinded for the intervention, causing a potential bias.

Frozen-thawed embryo transfers in natural cycles with spontaneous or induced ovulation: the search for the best protocol continues.

STUDY QUESTION: Is natural cycle frozen-thawed embryo transfer (NC-FET) associated with better clinical pregnancy rates (CPR) when compared to modified natural cycle frozen-thawed embryo transfer (mNC-FET)? SUMMARY ANSWER: NC-FET is associated with a higher CPR compared to mNC-FET. WHAT IS KNOWN ALREADY: There is conflicting evidence regarding the impact of hCG triggering on clinical outcomes after frozen-thawed embryo transfer (FET), and information on the effect of luteal phase support (LPS) is lacking. STUDY DESIGN, SIZE, DURATION: This retrospective study included all (n = 2353) consecutive cycles with FET of vitrified cleavage and blastocyst stage embryos warmed between January 2010 and April 2015 in a tertiary centre. The FET cycles were grouped by type as follows: NC (n = 501), NC + LPS (n = 828) or mNC + LPS (n = 1024). Artificial cycles were excluded from the analysis. PARTICIPANTS/MATERIALS, SETTING, METHODS: We performed mixed-effect multilevel multivariable regression analysis to account for the clustering of FETs using embryos derived from the same patient and/or ovarian stimulation cycle. Adjustment for the following potential confounders was also performed: female age at oocyte retrieval, number of oocytes retrieved, fresh cycle pregnancy outcome, embryo transfer rank, number of embryos transferred, embryo stage and grade and endometrial thickness. Bonferroni adjustment for multiple comparisons was performed whenever indicated. MAIN RESULTS AND THE ROLE OF CHANCE: The unadjusted CPR per cycle was significantly higher in the NC-FET group (46.9%) when compared with the mNC-FET + LPS groups (29.7%, P < 0.001) but not the NC-FET + LPS group (39.9%, P = 0.069). The lower clinical performance of mNC-FET + LPS remained significant even after adjusting for potential confounders [adjusted odds ratio (95% CI) compared to the NC-FET groups: 2.18 (1.64-2.90) and 1.67 (1.31-2.12) for the NC-FET and NC-FET + LPS groups, respectively]. A sensitivity analysis restricting the sample only to the first FET performed by the couple in our centre was also performed. The predicted CPR in this multivariable logistic regression model remained significantly higher in the NC-FET (53.9%) and NC-FET + LPS (44.9%) groups when compared to mNC-FET + LPS (34.2%, all Bonferroni-adjusted pairwise comparisons with P ≤ 0.01). LIMITATIONS, REASONS FOR CAUTION: The interpretation of the findings of this study is limited by the retrospective nature of the analysis and the potential for unmeasured confounding. WIDER IMPLICATIONS OF THE FINDINGS: The use of mNC-FET, using hCG triggering or progesterone supplementation, should be reconsidered in light of the potential negative effect on pregnancy outcome. STUDY FUNDING/COMPETING INTERESTS: None. TRIAL REGISTRATION NUMBER: N/A.

What is the optimal duration of progesterone administration before transferring a vitrified-warmed cleavage stage embryo? A randomized controlled trial.

STUDY QUESTION: What is the impact on clinical pregnancy rates when vitrified cleavage stage Day 3 embryos, warmed and cultured overnight to Day 4, are transferred on the 3rd or 5th day of progesterone administration in an artificial cycle? SUMMARY ANSWER: Clinical pregnancy rates are similar when transferring a vitrified-warmed cleavage stage Day 3 embryo after overnight culture on the 3rd or 5th day of progesterone administration. WHAT IS KNOWN ALREADY: In artificially prepared cycles, progesterone supplementation is generally started 3 days before embryo transfer, although the optimal length of exposure to progesterone before frozen embryo transfer (FET) has not been established. However, in a natural cycle, serum progesterone levels start to rise before ovulation, due to the LH-stimulated production by the peripheral granulosa cells. Hence, it could be postulated that progesterone supplementation before embryo transfer in an artificial cycle should start earlier or even later. STUDY DESIGN, SIZE, DURATION: Prospective, randomized controlled trial, encompassing 300 patients who had embryos frozen on Day 3 and who underwent FET in an artificial cycle. Between 1 November 2012 and 31 December 2014, 300 patients were allocated to one of two groups as soon as endometrial thickness reached ≥7 mm on ultrasound after estrogen supplementation. A computer-generated randomization list was used, not concealed to the physicians. Each patient was enrolled into the study only once. FET was performed on the fifth day of progesterone supplementation in Group A, whereas in Group B, FET was performed on the third day of vaginal micronized progesterone administration. Embryos were thawed the day before transfer and after overnight culture, one or two Day 4 embryos were transferred. PARTICIPANTS/MATERIALS, SETTING, METHODS: One hundred and fifty patients in Group A received 5 days of vaginal micronized progesterone tablets and one hundred and fifty patients in Group B received 3 days of micronized progesterone vaginally before FET. In Group A, 13 patients did not have an embryo transfer, compared with 12 patients in Group B. MAIN RESULTS AND THE ROLE OF CHANCE: Clinical pregnancy rates did not differ significantly between both groups (37/137 (27.0%) in Group A versus 26/138 (18.8%) in Group B (OR 1.6 (CI 0.9-2.82), ITALIC! P = 0.11). However, early pregnancy loss was significantly higher in Group B (32/58 (55.2%)) compared with Group A (21/58 (36.2%)) (OR 0.46 (CI 0.22-0.97), ITALIC! P = 0.04). LIMITATIONS, REASONS FOR CAUTION: Although no statistically significant difference was seen in the primary outcome, the study may have been underpowered to detect smaller differences. The study was also not blinded and patients were aware of the exact duration of progesterone supplementation. WIDER IMPLICATIONS OF THE FINDINGS: This is the first randomized controlled trial to show that duration of progesterone administration in an artificially prepared FET cycle may modulate cycle outcome and that too short progesterone supplementation might be deleterious. STUDY FUNDING/COMPETING INTERESTS: No external finance was involved in this study. All authors declare to have no conflict of interest with regard to this trial. TRIAL REGISTRATION NUMBER: The trial was registered at clinicaltrials.gov (NCT01940653). TRIAL REGISTRATION DATE: 9 September 2013. DATE OF FIRST PATIENT'S ENROLLMENT: 1 November 2012.