Natural Cycle IVF Research Articles

P-774 Conventional-IVF versus NC-IVF: unravelling the origins of fetal cardiac programming in ART

Abstract Study question Do fetuses from natural cycle IVF (NC-IVF) present signs of cardiac remodeling and suboptimal function similar to those observed in fetuses from conventional IVF (cIVF)? Summary answer Fetuses from both NC-IVF and cIVF present signs of fetal cardiac remodeling and suboptimal function as compared to spontaneously conceived fetuses (SC) from fertile couples. What is known already Previous publications have demonstrated that fetuses conceived by IVF present cardiac remodeling and suboptimal function. These fetuses show dilated atria, more globular and thicker ventricles, reduced longitudinal motion, and impaired relaxation. However, the pregnancies included in these studies were obtained following cIVF. In IVF cycles, ovarian stimulation has an impact on the oocyte quality and the endometrial milieu that may potentially affect perinatal results and fetal cardiovascular programming. Our aim was to compare cardiac morphometry and myocardial function in fetuses conceived by cIVF with those obtained after NC-IVF, without ovarian stimulation. Study design, size, duration This is a nested case-control study of 120 singleton pregnancies within a prospective cohort recruited from 2017 to 2021, including 40 SC from fertile couples, 40 following NC-IVF and 40 after cIVF with fresh embryo transfer, matched by maternal age, ethnicity, and gestational age at scan. IVF pregnancies were recruited from a single assisted reproduction center, ensuring homogeneity in ovarian stimulation protocols, laboratory procedures, and embryo culture conditions. Participants/materials, setting, methods The study protocol included prospective collection of parental demographics, reproductive and ART data, a fetal ultrasound scan at 28-34 weeks assessing biometry, feto-placental Doppler and morphological and functional echocardiography, and perinatal outcomes. Comparisons between groups were adjusted by gestational age and fetal weight at scan, and birthweight centile. Oocyte donation and PGT cycles were exclusion criteria. All the laboratory procedures including gamete manipulation, fertilization methods and embryo culture conditions were identical for NC-IVF and cIVF. Main results and the role of chance There were no significant differences in demographic data, perinatal outcomes, biometry and feto-placental Doppler parameters between the study groups. Reproductive data and IVF indications were also similar among the IVF groups. As compared to the SC, both IVF groups showed significant signs of fetal cardiac remodeling (higher cardio-thoracic ratio: cIVF mean 0.31 [SD 0.04]* versus NC-IVF 0.31 [0.03]* versus SC 0.28 [0.04], adjusted P-value <0.001; larger right atria-to-heart ratio: cIVF 19.1% [3.0]*† versus NC-IVF 18.8% [3.3]* versus SC 17.4% [2.9], adjusted P-value <0.001; increased relative wall thickness: c IVF 0.80 [0.2]* versus NC-IVF 0.85 [0.3]* versus SC 0.72 [0.3], adjusted P-value <0.001) and suboptimal function (tricuspid ring displacement (mm): cIVF 7.1 [0.8]* versus NC-IVF 7.3 [0.9]* versus SC 7.5 [1.4], adjusted P-value 0.003; left myocardial performance index: cIVF 0.50 [0.06]* versus NC-IVF 0.49 [0.06]* versus SC 0.48 [0.08], adjusted P-value <0.001). * Adjusted P value <0.05 as compared with SC. † Adjusted P value <0.05 as compared to NC- IVF. Limitations, reasons for caution The sample size was limited by the difficulty in recruiting viable pregnancies obtained by NC-IVF from a single center. The reported cardiac changes are subclinical and, although they are recognized as potential cardiovascular risk factors, their association with the long-term cardiovascular disease in these subjects remains to be proven. Wider implications of the findings Our findings contribute to assess the safety of different ART procedures in terms of cardiac performance in fetal life, before the influence of postnatal factors, in order to unravel the origins of fetal cardiac remodeling in ART. Studies evaluating the long-term health in this population are needed. Trial registration number Not applicable

P-674 Rescue oocyte collection: a strategy to reduce cycle cancellations in natural/natural modified IVF/ ICSI cycles with luteinising hormone (LH) surge among poor responder patients

Abstract Study question Can an early oocyte collection (OC) avoid cycle cancellation due to spontaneous ovulation in poor responders undergoing natural/ natural modified (N/NM) cycle-IVF? Summary answer Rescue OC may prevent premature ovulation following spontaneous LH surge in N/NM-IVF cycles allowing retrieval of mature oocytes, high-grade embryos that may result in livebirths. What is known already Natural IVF cycles carry an inherent higher risk of spontaneous LH surge and ovulation before OC. The introduction of gonadotropin releasing hormone antagonist with low-dose gonadotropin add-back has reduced these risks.Timing of ovulation trigger and trigger to OC interval are important to balance the risks of spontaneous ovulation with the chance of retrieving mature oocyte(s). In the absence of LH surge, the trigger to OC interval is normally 35 hours. However, it is challenging to schedule OC once LH surge has occurred.The effectiveness of rescue OC following LH surge has not been well explored. Study design, size, duration This is a retrospective analysis of all NC/NM-IVF/ICSI cycles in poor responders who had spontaneous urinary LH surge from over a period of 3 years, across five Fertility Centres under one company sharing the same treatment protocol. Participants/materials, setting, methods All women fulfilling the Bologna criteria for poor ovarian response underwent IVF/ICSI cycles with NC/ NM protocol. The study population included those who had a positive urinary LH surge without or despite the use of antagonist. A rescue OC scheduled 18 to 24 hours after a spontaneous urinary LH surge. Choriogonadotropin alfa (Ovitrelle) 250 micg was administered as soon as the surge was detected. Patients were also given indomethacin 8 hourly until OC. Main results and the role of chance Amongst 735 NC/NM-IVF/ ICSI cycles in poor responder women during the study period, 54 cycles (7.3%) had spontaneous urinary LH surge. Twenty-eight cycles were with NC-IVF and 26 NM-IVF protocol. Only 8 (14.8%) cycles did not progress to OC due to spontaneous ovulation. In 46 (85.2%) of cycles, at least one oocyte was successfully retrieved, with a total of59 retrieved oocytes. ICSI cycles identified at least one mature oocyte in 82% of the cycles. Fertilisation rate with IVF and ICSI cycles combined was 49.1% and at least one cleavage-stage embryo was created from 24 (44.4%) of all cycles (52.2% of retrieved cycles). High-grade embryo(s) was obtained in 42.5% of all cycles. Clinical pregnancy rate (CPR) and live birth rate (LBR) per embryo transfer were 18.7% and12.5%, respectively. Limitations, reasons for caution This study was retrospective in nature, without a comparator group. Combination of both NC-IVF and NM-IVF might not have implications in practical terms. Use ofindomethacin also could have delayed ovulation. Although population size was as expected for a rare event, it may not be adequate for a precise LBR. Wider implications of the findings An early scheduling of OC in the event of LH surge is an effective way to reduce cycle cancellation rate which is a risk in NC/NM-IVF cycles. It also can potentially result in livebirths. This approach may encourage clinicians practising NC/NM-IVF to test and validate our findings. Trial registration number not applicable

Ibuprofen delays ovulation by several hours: prospective controlled study in natural cycles with HCG-triggered ovulation

Research questionDoes ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), delay ovulation? DesignTwo-stage, proof-of-concept, controlled study, assessing the percentage of non-ovulated follicles 42 h after HCG injection in patients taking ibuprofen. The intervention group consisted of women undergoing natural cycle IVF treatment taking ibuprofen 3 × 400 mg per day. The control group consisted of women undergoing timed sexual intercourse or intrauterine insemination. The proportion of patients with non-ovulated follicles in the ibuprofen group was first compared against a reference of 50% using a one-sample binomial test, and second against the proportion observed in the control group using an adjusted logistic regression. ResultsA total of 26 women were recruited in the ibuprofen intervention group. Twenty-five patients were recruited in the control group. The proportion of patients with delayed ovulation observed (22/26 [84.6%]; 95% CI 65.1% to 95.6%) was significantly higher than the reference of 50% (P < 0.001). In the control group, the proportion of patients with delayed ovulation was 20.0% ([5/25], 95% CI 6.8% to 40.7%). Compared with the ibuprofen group, a significantly increased probability of a delayed ovulation was found in the ibuprofen intervention group (adjusted OR 22.72, 95% CI 5.77 to 115; P < 0.001). Of the 22 women with delayed ovulation, oocytes were retrieved in 20 women (90.9%) and all oocytes were mature (metaphase II). ConclusionsWomen trying to conceive should avoid non-selective NSAIDs around the time of ovulation. Ibuprofen or other NSAID can be used to delay ovulation for several hours in assisted reproductive technology and other infertility treatments if required.

P-36 Hidden cause of decreased fertility rate during Grave's disease

Abstract Introduction Thyroid autoimmune disorders interfere with the physiology of reproduction, cause premature ovarianfailure, and mimic the early stage of menopause. Recently, no specific research was made to measure Grave's disease and infertility rates in young patients. Clinical Case Due to an inability to conceive for two years, a 24-year-old Caucasian female was referred to the clinic with typical symptoms and complaints of Grave's disease. She has a family history of Grave's disease and Diabetes mellitus. Ultrasound confirmed the presence of a highly vascularized non-homogeneous hyperplastic thyroid gland. A thyroid scan with Tc99m revealed generalized increased uptake. Laboratory investigations showed a decrease in TSH-!0.005mIU/ml (n.0.4mIU/ml - 4.0mIU/ml), elevated FT4-31.8 pmol/l (n.8.0pmol/l-22.0pmol/l), FT3- 9.69pmol/l (n3.4 pmol/l-6.76pmol/l) and positive Anti-TG -190.05 AU/ml (n&amp;gt;150), Anti-TPO - 75.7 IU/ml (n&amp;gt;75) Anti-TSHR-27.3 IU/l (n&amp;gt;1,5). Prolactin and gonadal hormones were within normal limits AMH - 1.8 ng/ml(n1.52ng/ml-9.95ng/ml), Fsh- 6mIU/ml(n3.9mIU/ml-12.4mIU/ml). The patient was started on Methimazole and Beta-blocker. While decreasing the Methimazole dosage for further discontinuation, disease recurrence developed, and a total thyroidectomy was performed. Post- operatively, the patient was maintained on Levothyroxine. After 6 months of follow-up due to irregular Levothyroxine intake, the patient reached a hypothyroid status, during which, the patient had 2 consecutive spontaneous pregnancies, from which, one ended with spontaneous miscarriage in the early weeks of pregnancy and another, ectopic pregnancy treated with right salpingectomy. HSG confirmed weak left fallopian tube patency. After several months of keeping TSH below 2.5 mIU/ml, IVF treatment was scheduled. The results of the infertility workup showed a decrease in ovarian reserve AMH - 0.163ng/ml (n1.52ng/ml-9.95ng/ml), Fsh-16.23 mIU/ml(n3.9mIU/ml- 12.4mIU/ml), due to it, modified natural cycle IVF was performed. She received 2 oocytes and 2 embryos. One high-grade blastocyst was transferred in a fresh cycle that ended with pregnancy and delivery. The child was born without a genetic disorder but with natal teeth. Conclusion This is a rare case of infertility with diminished ovarian reserve due to Grave's disease. A pregnancy was reached by proper correction of thyroid hormonal parameters and modified natural cycle IVF. It indicates a possible need for close monitoring of the functional ovarian reserve in patients planning pregnancy even at the young age group.

FRI558 Hidden Cause Of Decreased Fertility Rate During Grave’s Disease

Abstract Disclosure: T. Kutchukhidze: None. T. Khurodze: None. Introduction: Thyroid autoimmune disorders interfere with the physiology of reproduction, cause premature ovarian aging, and mimic the early stage of menopause. Recently, no specific research was made to measure Grave’s disease and infertility rates in young patients. Case Report: Due to an inability to conceive for two years, a 24-year-old Caucasian female was referred to the clinic with typical symptoms and complaints of Grave's disease. She has a family history of Grave’s disease and Diabetes mellitus. Ultrasound confirmed the presence of a highly vascularized non-homogeneous hyperplastic thyroid gland. A thyroid scan with Tc99m revealed generalized increased uptake. Laboratory investigations showed a decrease in TSH-&amp;lt;0.005mIU/ml (n.0.4mIU/ml - 4.0mIU/ml), elevated FT4-31.8 pmol/l (n.8.0pmol/l-22.0pmol/l), FT3- 9.69pmol/l (n3.4 pmol/l-6.76pmol/l) and positive Anti-TG -190.05 AU/ml (n&amp;gt;150), Anti-TPO -75.7 IU/ml (n&amp;gt;75) Anti-TSHR-27.3 IU/l (n&amp;gt;1,5). Prolactin and gonadal hormones were within normal limits AMH - 1.8 ng/ml(n1.52ng/ml-9.95ng/ml), FSH- 6mIU/ml(n3.9mIU/ml-12.4mIU/ml). The patient was started on Methimazole and Beta-blocker. While decreasing the Methimazole dosage for further discontinuation, disease recurrence developed, and a total thyroidectomy was performed. Postoperatively, the patient was maintained on Levothyroxine. After 6 months of follow-up due to irregular Levothyroxine intake, the patient reached a hypothyroid status, during which, the patient had 2 consecutive spontaneous pregnancies, from which, one ended with spontaneous miscarriage in the early weeks of pregnancy and another, ectopic pregnancy treated with right salpingectomy. HSG confirmed weak left fallopian tube patency. After several months of keeping TSH below 2.5 mIU/ml, IVF treatment was scheduled. The results of the infertility workup showed a decrease in ovarian reserve AMH - 0.163ng/ml (n1.52ng/ml-9.95ng/ml), FSH-16.23 mIU/ml(n3.9mIU/ml-12.4mIU/ml), due to it, modified natural cycle IVF was performed. She received 2 oocytes and 2 embryos. One high-grade blastocyst was transferred in a fresh cycle that ended with pregnancy and delivery. The child was born without a genetic disorder but with natal teeth. Conclusion: This is a rare case of infertility with diminished ovarian reserve due to Grave’s disease. A pregnancy was reached by proper correction of thyroid hormonal parameters and modified natural cycle IVF. It indicates a possible need for close monitoring of the functional ovarian reserve in patients planning pregnancy even in the young age group. Presentation: Friday, June 16, 2023

P-113 The performance of pregnancy prediction is improved in an updated deep-learning based embryo selection model: A retrospective validation study using 3960 single blastocyst transfer cycles

Abstract Study question Does increasing the size of a training dataset improve the performance of pregnancy (fetal heartbeat) prediction in a deep-learning model? Summary answer Yes. Increasing the training data for a deep-learning model for embryo selection improved prediction of the likelihood of implantation after single vitrified-warmed blastocyst transfer (SVBT). What is known already Recently, artificial intelligence (AI) for implantation prediction after blastocyst transfer has been extensively studied. AI can address the issue of subjective assessment for the selection of blastocyst transfer. Generally, the performance of deep learning models is said to improve by increasing the training dataset. However, to the best of our knowledge, there exists no study on the effect of increasing training data on the performance of pregnancy prediction on the same deep-learning model. Study design, size, duration A total of 3,960 SVBT cycles (1 patient,1 cycle) were retrospectively analyzed. Embryos were stratified according to SART age groups. The quality and scoring of embryos were assessed by iDAScore v1.0 (iDAV1; Vitrolife, Sweden), v2.0 (iDAV2; Vitrolife, Sweden), and Gardner grading. The discriminative performance of the pregnancy prediction for each embryo scoring model was compared using the area under the curve (AUC) of the receiver operating characteristic curve for each maternal age group. Participants/materials, setting, methods Embryos were cultured in the EmbryoScope+ and/or EmbryoScope Flex (Vitrolife). iDAV2 and iDAV1 were based on an identical deep-learning architecture, but the training data for iDAV2 has been increased with 15% more data. ICM and TE were annotated according to the Gardner grading system. The degree of blastocyst expansion was Grade 4 due to our freezing policy. Furthermore, Gardner's grading (GG) was stratified into four grades (A: AA, B: AB BA, C: BB, D: others). Main results and the role of chance The AUCs of the &amp;lt; 35 years age group (n = 757) for pregnancy prediction were 0.718 for iDAV1, 0.733 for iDAV2, and 0.694 for GG. The AUC of iDAV2 was significantly higher compared to GG (P &amp;lt; 0.05). For the 35–37 years age group (n = 821) the AUCs were 0.696, 0.712, and 0.695 for iDAV1, iDAV2, and GS, respectively, and were significantly different between iDAV1 and iDAV2 (P &amp;lt; 0.05). The AUCs of the 38–40 years age group (n = 1,007) were 0.698 for iDASV1, 0.706 for iDAV2, and 0.700 for GG and there was no significant difference. The AUCs of the 41–42 years age group (n = 715) were 0.734, 0.745, and 0.696 for iDAV1, iDAV2, and GS, respectively, and the AUC of iDAV2 was not significantly different compared to iDAV1 (P = 0.174) but significantly different compared to GG (P &amp;lt; 0.05). For the &amp;gt; 42 years age group (n = 660) AUCs were 0.685 for iDAV1, 0.698 for iDAV2, and 0.682 for GS and were not significantly different among groups. The AUCs of iDAV1, iDAV2, and GG in all ages were 0.736, 0.720, and 0.702, respectively. iDAV2 were significantly higher than iDAV1 and GG (p &amp;lt; 0.05). Limitations, reasons for caution This study was based on minimal stimulation and natural cycle IVF treatment, and a freeze-all strategy whereby all transferred blastocysts had previously been vitrified. Therefore, we had only a few cycles with elective blastocyst transfer. In addition, this study was retrospective in nature. Wider implications of the findings For all age groups, iDAV2 had a higher AUC than iDAV1, although a significant difference was only observed for the young age group. This result suggests that the increased dataset used for the development of iDAV2 improved the performance of pregnancy prediction for SVBT in the deep-learning model. Trial registration number not applicable

Low-dose clomiphene citrate does not reduce implantation and live birth rates in otherwise unstimulated modified natural cycle IVF—retrospective cohort study

Research questionDoes antioestrogen effect of clomiphene citrate (CC) on the endometrium reduce implantation and thereby decrease pregnancy and live birth rate per transferred embryo?MethodsIn this cohort, unstimulated IVF cycles modified with clomiphene citrate (CC-NC-IVF) and unstimulated, natural IVF cycles (NC-IVF) conducted between 2011 and 2016 were included. CC was applied in a dosage of 25mcg per day, starting on cycle day 7 until ovulation trigger day. Primary outcomes were clinical pregnancy rate, defined as amniotic sac visible in ultrasound, and live birth rate per transferred embryo. Miscarriage rate calculated as amniotic sac not ending in a live birth was secondary outcome. A modified mixed-effect Poisson regression model was applied, and adjustments were made for female age, parity, type and cause of infertility. Additionally, stratification by parity and age was performed.ResultsFour hundred and ninety-nine couples underwent a total of 1042 IVF cycles, 453 being NC-IVF and 589 being CC-NC-IVF cycles. Baseline characteristics of both groups did not differ. Addition of CC did neither decrease clinical pregnancy rate (aRR 0.86; 95% CI 0.67–1.12) nor live birth rate per transferred embryo (aRR 0.84; 95% CI 0.62–1.13) in comparison with NC-IVF. Miscarriage rate did not differ between CC-NC-IVF and NC-IVF (aRR 0.95; 95% CI 0.57–1.57).ConclusionLow-dose CC does not reduce pregnancy or live birth rate per transferred embryo. It can be used in infertility treatment without negatively affecting the endometrium and implantation.

Oocyte maturity, oocyte fertilization and cleavage-stage embryo morphology are better in natural compared with high-dose gonadotrophin stimulated IVF cycles

Research questionDoes high-dose gonadotrophin stimulation have an effect on oocyte and early-stage embryo development? DesignThis was a retrospective study including 616 natural cycle IVF (NC-IVF) and 167 conventional IVF (cIVF) cycles. In total, 2110 oocytes were retrieved and analysed in fresh cycles. In NC-IVF, only human chorionic gonadotrophin was applied to trigger ovulation. In cIVF, antagonist protocols with daily 150–300 IU of human menopausal gonadotrophins were performed. The effect of gonadotrophins on oocyte and early-stage embryo development was analysed. Primary outcomes were the occurrence of mature (metaphase II) oocytes, zygotes and embryos with good morphology at the cleavage stage 2 days after oocyte retrieval. ResultsThe mature oocyte rate (number of mature oocytes/number of retrieved oocytes) was higher in NC-IVF than cIVF cycles (89% versus 82%, adjusted odds ratio [aOR] 1.79, P = 0.001), as was the zygote rate per oocyte retrieved (70% versus 58%, aOR 1.76, P = 0.001) and the zygote rate per mature oocyte (79% versus 71%, aOR 1.62, P = 0.001). The percentage of zygotes that developed into cleavage-stage embryos was no different. For the transferred embryos, the probability of having a good embryo morphology with four blastomeres and a fragmentation of <10% (score 0) in cleavage-stage embryos was found to be higher in NC-IVF (proportional aOR for four blastomeres 2.00, P < 0.001; aOR 1.87 for a fragmentation score of 0, P = 0.003). ConclusionsOocyte maturity, oocyte fertilization and morphology of the cleavage-stage embryo are affected by high-dose gonadotrophin stimulation in fresh IVF cycles.

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

ObjectiveDoes the dose or type of gonadotropin affect the reproductive outcomes of poor responders undergoing IVF in a modified natural cycle (MNC-IVF)? Study DesignThis 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. ResultsIn 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). ConclusionsThe type and daily dose of gonadotropins do not affect the reproductive outcome of poor responders undergoing MNC-IVF.

P-593 Low dose clomiphene citrate does not reduce implantation rates - a cohort study based on modified Natural Cycle IVF

Abstract Study question Does low dose clomiphene citrate (CC) reduce implantation and eventually pregnancy and live birth rates? Summary answer Low dose CC does not reduce implantation rate and pregnancy and live birth rates – based on the model of modified Natural Cycle IVF (NC-IVF). What is known already CC is commonly used for ovulation induction in the treatment of anovulation or idiopathic infertility. It is also added to NC-IVF cycles to mildly stimulate follicular growth and to inhibit LH surge. CC reduces endometrial thickness and affects endometrial function. Therefore it is assumed that CC negatively affects implantation and thereby reduced pregnancy and live birth per embryo. However, previous studies have shown inconsistent results as previous studies mainly calculated pregnancy rates per cycle but not implantation rate per embryo. Study design, size, duration This cohort study included embryos transferred in NC–IVF and CC-NC-IVF cycles. Women with a maximum age of 42 years were treated at a university hospital between 2011 and 2016. Clinical pregnancy rate and live birth rate per embryo transferred and miscarriage rate per amniotic sac were calculated. Participants/materials, setting, methods A daily dose of 25mg of CC starting on day 5-7 of the cycle until the day of ovulation trigger was applied. A modified mixed effect Poisson regression model was used to account for the number of cycles in the same women and the number of embryos in the same cycle to achieve rate ratios (RR). Adjustment for maternal age, parity, type of infertility, duration of subfertility and indication for IVF were made. Main results and the role of chance 499 couples underwent a total of 1043 IVF cycles, 453 NC-IVF and 590 CC-NC-IVF cycles. Baseline characteristics of both groups were not different. The additional administration of CC did neither decrease clinical pregnancy rate (aRR 1.16; 95% CI: 0.90 – 1.50)[MV1] nor live birth rate per transferred embryo (aRR 1.20; 95% CI: 0.89 – 1.62). Miscarriage rate was also not different in CC-NC-IVF compared to NC-IVF (aRR 1.05; 95%: CI 0.63 – 1.76). Limitations, reasons for caution This study does not allow to draw any conclusions regarding the effect of higher CC dosages. As randomization was not performed, some bias regarding the choice of IVF treatment cannot be completely excluded. Wider implications of the findings As this study revealed for the first time that low dose CC does not affect implantation, low does CC can be used for many different treatments. However, further studies are required to evaluate if this also applies to higher CC dosages. Trial registration number not applicable

Effect of dominant follicle status at the time of retrieval on the clinical outcomes in natural cycle IVF combined with immature oocyte treatment.

Objective: It is commonly believed that the oocytes from small follicles are unhealthy when a dominant follicle (DF) is recruited in the ovaries, especially when the DF is ovulated. This study aims to confirm whether the presence or ovulation of DF at the time of retrieval affects the clinical outcome of the natural cycle IVF with in vitro maturation (NC-IVF/M) treatment.Methods: Data were collected from 446 women with regular menstrual cycle and 536 retrieval cycles using NC-IVF/M treatment. The cycles were divided into three groups based on the results of the oocyte retrieval cycle. Group A covers the collection of oocytes from the DF and small follicles; Group B incorporates failed oocyte retrieval from DF and then the oocytes are retrieved only from small follicles; and Group C includes the retrieval of oocytes only from small follicles accompanied with an ovulated DF. Furthermore, Group B and C have subgroups to include whether in vivo matured oocytes were obtained from small follicles. Following aspiration of DF and small follicles, mature oocytes were inseminated on the date of retrieval by intracytoplasmic sperm injection (ICSI) and the immature oocytes were matured in vitro. If the immature oocytes were matured in vitro, they were inseminated using ICSI, and then the embryos obtained from in vivo and in vitro matured oocytes were transferred accordingly.Results: The oocytes from DF were successfully retrieved in 445 cycles (83.0%), failed to be retrieved in 54 cycles (10.1%) and ovulated in 37 cycles (6.9%). In Group A, an average of 2.0 ± 1.7 mature oocytes were retrieved, which was significantly higher than the average of Group B, with 1.3 ± 1.3 matured oocytes and Group C, with an average of 1.1 ± 1.5 matured oocytes (P < 0.01). However, the average number of immature oocytes retrieved from each group show no difference among the three groups. There was no significant difference in maturation rates of immature oocytes, fertilization rates among the three groups. The clinical pregnancy rate per transfer cycle is 34.5%, 34.6% and 25.7% in Group A, B and C, respectively. No significant differences were observed in embryonic development and implantation capacity in Group B and C in comparison to Group A. And there was no significant difference in clinical pregnancy, implantation, live birth and miscarriage rates among the three groups. No significant differences were observed in the developmental and implantation capacity according to with or without in vivo matured oocytes were retrieved in Group B and Group C.Conclusion: The presence or ovulation of the dominant follicle from the ovaries does not significantly influence the developmental and implantation capacity of immature oocytes retrieved from small follicles, suggesting that NC-IVF/M is a promising treatment option for women without ovarian stimulation.

High dose gonadotropin stimulation increases endometrial thickness but this gonadotropin induced thickening does not have an effect on implantation

IntroductionEndometrial thickness <8 mm is related with lower pregnancy rates. This raises the question if endometrial thickness can be increased by gonadotropin stimulation to increase estradiol (E2) concentration and if such an artificial thickening of the endometrium has an effect on implantation. A model to address this question is the comparison of endometrial thickness and outcome parameters in conventional gonadotropin stimulated IVF (cIVF) compared to unstimulated natural cycle IVF (NC-IVF). Material and methodsRetrospective study including 235 cIVF and 616 NC-IVF cycles without embryo selection and with fresh transfer on day 2 and 3 from 2015 to 2019. Endometrial and E2 measurements were included and analysed between day -4 and -2 (0 = day of aspiration). The effects of E2 on endometrial thickness, endometrial growth and the effect of endometrial thickness on implantation rates and live births were analysed. ResultsEndometrial thickness was found to be higher in cIVF compared to NC-IVF (p < 0.001). On day -2, the day when ovulation was triggered, mean endometrial thickness was 9.75 ± 2.05 mm and 8.12 ± 1.66 mm, respectively. The increase in endometrial thickness slowed down with increasing E2 concentrations (time x estradiol concentration: -0.19, p = 0.010). Implantation rates were not significantly different in cIVF and NC-IVF cycles (clinical pregnancy rate: 19.1% vs. 15.4% p = 0.2; live birth rate: 12.8% vs. 11.7%, p = 0.8). ConclusionsEndometrial growth dynamic is different and endometrium is thicker in cIVF compared to NC-IVF. Pregnancy and live birth rates are not different. Gonadotropin induced thickening of the endometrium does not appear to improve implantation.

Optimal Timing of Ovulation Triggering to Achieve Highest Success Rates in Natural Cycles-An Analysis Based on Follicle Size and Oestradiol Concentration in Natural Cycle IVF.

IntroductionTiming of ovulation triggering is essential in infertility treatments including treatments based on natural menstrual cycles. However, data on follicle size and oestradiol (E2) concentration are limited. Therefore, the model of natural cycle IVF (NC-IVF) was applied to provide more detailed information on these parameters to better schedule the optimal time for triggering ovulation.Materials and MethodsA retrospective cross-sectional analysis of 606 monofollicular NC-IVF cycles was performed at a university-based IVF centre from 2016 to 2019. Follicle size and E2 and LH serum concentrations were evaluated on day -5 to 0 (day 0 = day of oocyte retrieval). Ovulation was triggered if follicle size was 14–22 mm. Patients with irregular cycles, endometriosis >II°, cycles with azoospermia or cryptozoospermia and cycles with inconsistent data were excluded. All parameters were analysed inter- and intraindividually, and associations of the parameters were evaluated. Associations were adjusted for age, cause of infertility and number of previous transfers.ResultsThe mean age of women undergoing NC-IVF was 35.8 ± 4.0 years. Follicle size increased by 1.04 ± 0.03 mm, and E2 concentration by 167 ± 11.0 pmol/l per day.Based on a multivariate adjusted mixed model with follicle size, E2 and their interaction, the number of retrieved oocytes was associated with E2 concentration (aOR 1.91, 95% CI: 1.03–3.56; p = 0.040). Maturity of oocytes was associated not only with E2 concentration (aOR 2.01, 95% CI: 1.17–3.45; p = 0.011) but also with follicle size (aOR 1.27, 95% CI: 1.01–1.60; p = 0.039), as was the interaction of both parameters (aOR 0.96, 95% CI: 0.93–0.99; p = 0.017).LH surge was calculated to start in 25% of cases at an E2 level of 637 pmol/l, in 50% of cases at 911 pmol/l and in 75% of cases at an E2 level of 1,480 pmol/l.The live birth rate per follicle aspiration cycle was (non-significantly) higher in cycles with follicles sizes at the time of oocyte retrieval of 18–22 mm (7.7%–12.5%) versus in cycles with follicles sizes of 14–17 mm (1.6%–4.3%).ConclusionThe study contributes to an optimization of infertility treatments involving natural cycles. The study gives guidance about the number of days required after follicle monitoring to schedule the optimal time for triggering ovulation.

Development of a predictive model for luteal phase oocyte retrieval in poor responders undergoing natural cycle IVF

The aim of this study is the development of a prediction model indicating successful application of Oocyte Retrieval performed during the Luteal Phase (LuPOR) in poor responders, as defined by the retrieval of at least one MII oocyte. Recruitment included 1688 poor responders diagnosed as per Bologna Criteria, undergoing natural cycle ICSI between 2012 and 2020. Oocyte collections were performed during the follicular phase and during the luteal phase similarly. Antral Follicle Count (AFC), Estradiol (E2) levels evaluated on both trigger days prior to Follicular Phase Oocyte Retrieval (FoPOR) and LuPOR, and the number of small follicles 8–12 mm that were not aspirated during FoPOR were identified as predictive factors indicative of an efficient LuPOR practice with an Area Under the Curve (AUC) of 0.86, 0.86, 0.89 as well as 0.82 respectively. The combination of the above-mentioned characteristics into a prediction model provided an AUC of 0.88, specificity and a sensitivity of 0.73 and 0.94 respectively and an accuracy of 0.89. The model provided a positive predictive value (PPV) of 93.5% and a negative predictive value (NPV) of 46.8%. The clinical conclusion of the present study aims to be of added value to the clinician, by providing a prediction model defining the POR population benefiting from LuPOR. The high PPV of this model may renders this tool helpful for the practitioner that considers LuPOR.

VP23.01: Cardiac remodelling in fetuses conceived following natural cycle IVF versus conventional IVF

VP23.01: Cardiac remodelling in fetuses conceived following natural cycle IVF versus conventional IVF

Gonadotrophin stimulation reduces follicular fluid hormone concentrations and disrupts their quantitative association with cumulus cell mRNA

Research questionDo follicular fluid hormone concentrations and the mRNA expression of LHCG, FSH and androgen receptors, aromatase and anti-Müllerian hormone (AMH) in cumulus granulosa cells differ in naturally matured and stimulated follicles? DesignCross-sectional study involving 57 natural cycle IVF (NC-IVF) and 36 conventional gonadotrophin-stimulated IVF (cIVF) cycles performed between 2014 and 2016. cIVF was performed by ovarian stimulation with human menopausal gonadotrophin and gonadotrophin-releasing hormone antagonists. Hormone concentrations were determined in the follicular fluid of the leading follicle, and mRNA concentrations were quantified by reverse transcription polymerase chain reaction in RNA extracted from granulosa cells of the cumulus oophorus complex obtained from these fluids. ResultsFollicular fluid hormone concentrations were significantly lower in cIVF compared with NC-IVF follicles. Median concentrations were 0.50 and 14.5 mIU/ml for LH (P < 0.001), 16.1 and 46.5 nmol/l for testosterone (P < 0.001), 1270 and 2675 nmol/l for oestradiol (P < 0.001), and 12.3 and 28.9 pmol/l for AMH (P < 0.001), respectively. In cumulus granulosa cells, mRNA concentrations for LH receptor, FSH receptor, androgen receptor, aromatase and AMH did not differ between cIVF and NC-IVF follicles. Several hormone and mRNA concentrations were quantitatively associated in natural cycles such as follicular fluid AMH and cumulus granulosa cells AMH RNA (r2 = 0.107, P = 0.013), follicular fluid testosterone and cumulus granulosa cell AMH RNA (r2 = 0.158, P = 0.002), follicular fluid oestradiol and cumulus granulosa cell AMH RNA (r2 = 0.105, P = 0.014) and follicular fluid oestradiol and aromatase (r2 = 0.113, P = 0.011). In contrast, these associations were not observed in stimulated cycles. ConclusionThese findings indicate some effects of gonadotrophin stimulation on follicular physiology, which could be a cause for the previously suggested lower oocyte quality in cIVF compared with NC-IVF.

P–693 Gonadotropin stimulation reduces the implantation and live birth but not the miscarriage rate – a study based on the comparison of stimulated and unstimulated IVF

Abstract Study question Does gonadotropin stimulation in conventional IVF (cIVF) affect the implantation, miscarriage and live birth rates? Summary answer Gonadotropin stimulation negatively affects the implantation and live birth but not the miscarriage rate in IVF treatments. What is known already Literature hypothesizes that embryos derived from unstimulated, natural cycle IVF (NC-IVF) have a higher implantation potential compared to embryos from cIVF. In NC-IVF, recruitment of the leading follicle is based on natural selection. Hormonal stimulation might not only affect the embryo but also endometrial function. It’s possible to compare outcomes of NC-IVF and cIVF if cIVF is performed without embryo selection, in other words, if only those zygotes, which will be transferred 1–2 days later, are left in culture and all other zygotes are cryopreserved. To test this hypothesis, we compared success rates in NC-IVF and in cIVF. Study design, size, duration We performed a cohort study from 2011–2016 including data on IVF cycles with transfer of fresh embryos on day 2–3 at a University based infertility center. Our sample consisted of 640 women with 1482 embryos transferred in 996 cycles. We defined implantation rate as the number of sonograhically detected amniotic sacs per transferred embryos. Data originated from the Swiss ART registry “FIVNAT” and the Bern IVF Cohort and was completed using medical and delivery records. Participants/materials, setting, methods We defined NC-IVF as IVF without stimulation of follicular growth and cIVF as IVF with gonadotropin stimulation ≥75 IE/d and &amp;gt;3 retrieved oocytes. We performed zygote, but not embryo selection and transferred embryos on day 2–3. We calculated implantation and live birth per transferred embryo as binary outcomes using bi- and multivariable multilevel logistic regression models accounting for two clusters; the women and the cycle; and adjusting for maternal and infertility characteristics using STATA. Main results and the role of chance Age of women (p = 0.531), parity (p = 0.194) and type of infertility (primary vs secondary) (p = 0.463) did not differ between women undergoing NC-IVF or cIVF. In NC-IVF, 468 (31.6%) embryos were transferred, 450 as single, 18 as double transfers. In cIVF, 1014 (68.4%) embryos were transferred, 91 as single, 830 as double and 93 as triple transfers. Implantation rate was higher in NC-IVF. In NC-IVF 80 (17.1%) and in cIVF 132 (13.0%) embryos developed into an amniotic sac (OR 1.58; 95% CI 1.01–2.46; p = 0.042). After adjustment for maternal age (p &amp;lt; 0.001), parity (p &amp;lt; 0.001), type of infertility (p = 0.037), duration of subfertility and indication for IVF, aOR for implantation per transferred embryo increased to 1.87 (95% CI 1.21–2.91; p = 0.005). Miscarriage rate was similar. In NC-IVF and cIVF 25% (n = 20; n = 33) miscarried and 75% (n = 60; n = 99) ended in a live birth, respectively (OR 0.91; 95% CI 0.32–2.60; p = 0.855; aOR 1.0; 95% CI 0.42–2.36; p = 1.000). Live birth rate per transferred embryo was increased in NC-IVF; 60 of 468 (12.8%) embryos in NC-IVF compared to 99 of 1041 (9.8%) embryos in cIVF resulted in a live birth (OR 1.51; 95% CI 0.92–2.49; p = 0.106); and became significantly higher after adjustment (aOR 1.85; 95% CI 1.16–2.95; p = 0.010). Limitations, reasons for caution This study analyses observational data from a clinic offering NC-IVF and cIVF treatment as equivalent options. NC-IVF is a model for natural fertility and allows us to study the impact of gonadotropins. However, it is not a randomised study and therefore prone to selection bias. Wider implications of the findings: The study suggests that gonadotropin stimulation might reduce the implantation potential and subsequently live birth rates, by possibly affecting embryo and endometrium quality. Clinicians should consider lower gonadotropin doses for stimulation. Trial registration number Not applicable

P–332 Endometrium thickness is increased in gonadotropin stimulated IVF compared to unstimulated cycles, but this increase does not have a positive effect on pregnancy rate

Abstract Study question Is endometrial growth and endometrial thickness different in controlled ovarian stimulation (COS)-IVF compared to unstimulated cycles and does this have an effect on pregnancy rates? Summary answer Endometrial growth dynamic is different and endometrium is thicker in COS-IVF but this does not have a positive effect on pregnancy and live birth rates. What is known already Endometrial growth and endometrial thickness are a function of duration and concentration of estradiol (E2) stimulation. Endometrial thickness &amp;lt;8mm is related with lower pregnancy rates in IVF treatments. It is commonly assumed that an increase of endometrial thickness by increasing estrogen stimulation could have a positive effect on pregnancy rate. However, such a relationship has never been systematically analysed. Natural Cycle IVF (NC-IVF) is an ideal model to analyse the effect of high dose gonadotropin stimulation on several parameters such as thickness of endometrium and pregnancy rate. Study design, size, duration Retrospective single center, University based study including 235 COS-IVF and 616 NC-IVF cycles from 2015 to 2019. Polyfollicular COS-IVF cycles were only analysed until 09 2017 as embryo selection was introduced in Switzerland afterwards. Limiting the analysis to cycles without embryo selection enabled us to compare embryos derived from cIVF and NC-IVF. 1550 endometrial and 1068 E2 measurements were included in the analysis. Participants/materials, setting, methods Mean female age at the time when the cycles were performed was in NC-IVF 35.8±3.9y and in COS-IVF 34.9±4.2y (maximum 42y). Each woman performed on average 1.96±1.45 IVF cycles. Endometrial thickness and E2 serum concentrations were evaluated daily between day –4 and –2 (0=day of aspiration). Pregnancy and live birth rate were evaluated per transferred embryo. Statistically, student test and a repeated measure model and a logistic regression model both adjusted for age were used. Main results and the role of chance Endometrial thickness was different in COS-IVF and NC-IVF. At each time point endometrial thickness was found to be higher in COS-IVF compared to NC-IVF (p &amp;lt; 0.001 on days –4,–3, and –2). On day –2, the day when ovulation was triggered, mean endometrial thickness was 9.75 ±2.05mm in COS-IVF and 8.12 ±1.66mm in NC-IVF. Endometrial growth dynamic was also different in COS-IVF and NC-IVF. Endometrial thickness increased significantly faster in NC-IVF cycles (0.58mm/day [0.43,0.73]) than in cIVF cycles (0.22mm/day [–0.12, 0.55], Pval= 0.034). The increase of endometrial thickness per day was less pronounced if E2 concentrations were high (–0.19 [–0.34, 0.05]). Therefore it can be assumed that the observed differences in growth dynamics in both treatments are caused by differences in E2. Increased endometrial thickness in COS-IVF was not associated with higher success rate. There was no significant effect of endometrium thickness on pregnancy (Pval=0.318) and Live birth rate (Pval=0.461). Limitations, reasons for caution Pregnancy and live birth rates might be affected by more than just endometrial thickness. The study was only based on the thickness of the endometrium but not on its ultrasound pattern. Wider implications of the findings: Postponing the aspiration to allow endometrium to further proliferate has only a limited effect in COS-IVF. Increasing gonadotropin stimulation dosage just to increase endometrial thickness is not a feasible strategy to improve pregnancy rate. The need to apply high dosages of estrogen supplementation in thawing cycles need to be questioned. Trial registration number “not applicable”

P–609 The chances of one live birth rates after first ART cycle in minimal stimulation cycle IVF with letrozole only and natural cycle IVF

Abstract Study question Are one live birth rates (LBRs) similar in minimal stimulation cycle IVF with letrozole only and natural cycle IVF for the first ART cycle? Summary answer LBRs after first ART cycle in minimal stimulation cycle IVF with letrozole only are superior to natural cycle IVF. What is known already The addition of letrozole to gonadotropins in ovarian stimulation (OS) may reduce the risk of OHSS, but there is no significant difference were reported in ongoing pregnancy rate or number of oocytes retrieved in the letrozole + FSH group compared to the FSH only. No differences were also reported in clinical pregnancy rates or number of mature oocytes in the additional of letrozole in an GnRH antagonist protocol group compared to the GnRH antagonist group. There are no previous study comparing LBRs after first ART cycle in minimal stimulation cycle IVF with letrozole and natural cycle IVF. Study design, size, duration Data for this retrospective cohort study were obtained 643 women, 30–39 years of age started their first ART cycle at one private fertility clinic between January 2016- December 2019. Participants/materials, setting, methods A total of 643 women were scheduled their first oocyte retrieval cycle. 118 women started with letrozole (LE) and 525 women started natural cycle (NC). The main strategy for OS in our center is minimal stimulation and natural cycle IVF. Patients consulted with gynecologists to determine their treatment plan based on patients’ preference or their menstrual cycle. All pregnancies generated from oocyte retrieval during the first IVF cycle including fresh and frozen-thaw cycles were registered. Main results and the role of chance The number of retrieved oocytes and the normal fertilization rates were significantly higher in the LE than NC (4.4 vs 3.4, 77.6% vs 71.1%), p &amp;lt; 0.05 respectively). There was no significant difference in the clinical pregnancy rates (CPRs) per embryo transfer (ET) (fresh cleavage stage ET: 32.9% vs 28.0%, frozen-thaw blastocyst ET: 39.4% vs 44.9% ns). However, the CPRs and LBRs per oocyte retrieval (OR) were significantly higher in the LE group (39.0% vs 28.6, 33.9% vs 21.9%, p &amp;lt; 0.05 respectively). In a subsequent regression analyses, LBRs per OR of LE was significantly higher than NC as well. (adjusted OR = 1.63 (95% CI: 1.02–2.58, p = 0.041). Limitations, reasons for caution The strength of the present study was the use of a large cohort of women who underwent minimal stimulation IVF with letrozole only. Although our results are promising, limited by retrospective cohort study. These interpretations prompted the need for a perspective cohort study to evaluate the efficacy of letrozole. Wider implications of the findings: When comparing minimal stimulation IVF with letrozole only and natural cycle IVF, we found significantly higher LBRs per OR in minimal stimulation IVF with letrozole only, despite similar CPRs per ET. Trial registration number none

P–610 Optimal timing of ovulation triggering to achieve highest success rates in natural cycles – an analysis based on follicle size and estradiol concentration in NC-IVF

Abstract Study question What is the best follicle size, estradiol (E2) serum concentration and endometrial thickness to trigger ovulation in natural cycles? Summary answer Optimal follicles size is 18–22mm but estrogen concentration also need to be considered to maximize oocyte maturity and to minimize premature LH surge. What is known already Timing of the ovulation triggering is essential in infertility treatments based on natural menstrual cycles such as optimized vaginal intercourse, intrauterine inseminations and thawing cycles without hormone replacement therapy. Common parameters to define the day of ovulation triggering are the follicle size and the estrogen concentration. However, data on follicle size and estrogen concentration are either derived from longitudinal evaluations of few ideal participants, are not very detailed or were studied in stimulated cycles. The model of Natural Cycle IVF (NC-IVF) which provides more detailed information has never been used to study this issue. Study design, size, duration Retrospective cross sectional analysis of monofollicular NC-IVF cycles. Follicle size, E2 and LH serum concentrations and endometrial thickness were evaluated on day –5 to 0 (day 0 = day of aspiration). Ovulation was triggered with 5.000IE HCG 36h before aspiration if follicle size was 14–22mm. Patients with irregular cycles, endometriosis &amp;gt;II°, cycles with azoospermia or cryptozoospermia and with inconsistent data were excluded. 606 cycles from 290 women were analysed from 2016 to 2019. Participants/materials, setting, methods Mean age of women undergoing NC-IVF was 35.8±4.0y, median 36y [IQ-range: 34;39]. Each woman performed mean 2.1±1.4, median: 2 [IQ-range: 1–3] NC-IVF cycles at an university based IVF center. All parameters were analysed inter and intraindividually and associations were adjusted for maturity of oocyte, zygote development rate, embryo score, implantation rate and live birth rate. Associations were adjusted for age, cause of infertility and number of previous transfers. Main results and the role of chance Follicle size, E2 concentration and endometrial thickness increased constantly over time. The increase was computed for each cycle without considering any correlation intra patient, revealing an increase of follicle size by 1.04±0.64mm, an increase of E2 concentration by 167.3±76.8pmol/L and endometrial thickness by 0.69±0.59mm per day. Based on a multivariate adjusted model with follicle size, E2 and their interaction, number of retrieved oocytes was associated with E2 concentration (aOR 1.80, 95% CI 1.05–3.11; p = 0.034). Maturity of oocytes was associated not only with E2 concentration (aOR 1.84, 95% CI 1.15–2.94; p = 0.010) but also with follicle size (aOR 1.24, 95% CI 1.01–1.53; p = 0.037) and so was also the interaction of both parameters (aOR 0.96, 95% CI 0.94–0.99; p = 0.017). LH surge was calculated to start in 25% of cases at an E2 level of 545 pmol/l, in 50% of cases at 907pmol/l and in 75% of cases at an E2 level of 1531pmol/l. Live birth rate in cycles with follicles size 14–17 mm was 2.2–3.5% per initiated cycle and in cycles with follicle size 18–22mm 8.5–12.5%. Limitations, reasons for caution Cross sectional studies provides less precise information than longitudinal studies. Follicle size and endometrial thickness were evaluated by several physicians possibly causing some imprecision. Wider implications of the findings: There is a trend towards natural treatment cycles. The study contribute to an optimisation of infertility treatments involving natural cycles. The study gives guidance about the number of days required after a follicle monitoring to reach the optimal time for triggering ovulation. Trial registration number Not applicable