Optimal endometrial thickness in fresh and frozen-thaw in vitro fertilization cycles: an analysis of live birth rates from 96,000 autologous embryo transfers

Contributing factors for pregnancy outcomes in women with PCOS after their first FET treatment: a retrospective cohort study

OBJECTIVE

We aim to explore the contributing factors of clinical pregnancy outcomes in PCOS patients undergoing their first FET treatment.

METHODS

A retrospective analysis was conducted on 574 PCOS patients undergoing their first FET treatment at a private fertility center from January 2018 to December 2021.

RESULTS

During the first FET cycle of PCOS patients, progesterone levels (aOR 0.109, 95% CI 0.018-0.670) and endometrial thickness (EMT) (aOR 1.126, 95% CI 1.043-1.419) on the hCG trigger day were associated with the clinical pregnancy rate. Similarly, progesterone levels (aOR 0.055, 95% CI 0.007-0.420) and EMT (aOR 1.179, 95% CI 1.011-1.376) on the hCG trigger day were associated with the live birth rate. In addition, AFC (aOR 1.179, 95% CI 1.011-1.376) was found to be a risk factor for preterm delivery.

CONCLUSIONS

In women with PCOS undergoing their first FET, lower progesterone levels and higher EMT on hCG trigger day were associated with clinical pregnancy and live birth, and AFC was a risk factor for preterm delivery. During FET treatment, paying attention to the patient's endocrine indicators and follicle status may have a positive effect on predicting and improving the pregnancy outcome of PCOS patients.

Effect of a novel copper chloride gel on endometrial growth and function in healthy volunteers

RESEARCH QUESTION

Does the application of a micro-dose of copper chloride gel increase endometrial production of vascular endothelial growth factor (VEGF) without compromising endometrial function or producing embryo toxicity?

DESIGN

An estimate of optimal dose was made based on cell culture studies. Ten healthy participants received an initial uterine application of placebo gel, followed by copper chloride gel (37.5 μM, 75 μM, or 150 μM dose) in a later hormone replacement cycle. Endometrial biopsies (day 5.5 luteal) and pelvic ultrasound were carried out during each cycle to evaluate endometrial function and growth. Uterine fluid was assessed for residual copper levels on the day of biopsy, and copper chloride gel underwent mouse embryos assay assessment for potential embryo toxicity.

RESULTS

The copper gel significantly increased endometrial VEGF expression (quantitative polymerase chain reaction), and also increasing endometrial thickness by an average of 2.2 mm compared with matched control cycles. The copper gel did not adversely affect endometrial morphology or maturation (histological dating and molecular receptivity testing), and mouse embryos assay studies showed no evidence of embryo toxicity. Furthermore, uterine cavity flush samples mostly lacked copper, with only negligible amounts present in one sample.

CONCLUSION

Applying copper chloride gel to the uterine cavity upregulated endometrial VEGF and significantly increased endometrial thickness and volume. No adverse effects on the endometrium or embryos were observed. Copper chloride gels show promise for treating suboptimal endometrial thickness if the results of this study are confirmed by larger randomized controlled trials.

Protective effects of engineered Lactobacillus crispatus strains expressing G-CSF on thin endometrium of mice

STUDY QUESTION

Does recombinant Lactobacillus expressing granulocyte colony-stimulating factor (G-CSF) have a better protective effect than the current treatment of thin endometrium (TE)?

SUMMARY ANSWER

This study suggested that the intrauterine injection of Lactobacillus crispastus (L. crispastus)-pPG612-G-CSF has a positive effect on preventing TE induced by 95% alcohol in mice.

WHAT IS KNOWN ALREADY

TE has a negative impact on the success rate of ART in patients, and is usually caused by intrauterine surgery, endometrial infection, or hormone drugs. Exogenous G-CSF can promote endometrial vascular remodelling and increase endometrial receptivity and the embryo implantation rate. Moreover, Lactobacillus plays a crucial role in maintaining and regulating the local microecological balance of the reproductive tract, and it could be a delivery carrier of the endometrial repair drug G-CSF.

STUDY DESIGN, SIZE, DURATION

We constructed engineered L. crispastus strains expressing G-CSF. The mice were divided into five groups: (i) Control group (C, n = 28), uteri were treated with preheated saline solution via intrauterine injection on the third and sixth day of oestrus; (ii) Model group (M, n = 35), where uteri were treated with 95% alcohol on the third day of oestrus and preheated saline solution on the sixth day of oestrus via intrauterine injection; (iii) L. crispatus-pPG612-treatment group (L, n = 45), where uteri were treated with 95% alcohol on the third day of oestrus and 0.1 ml × 108 CFU/ml L. crispatus-pPG612 on the sixth day of oestrus via intrauterine injection; (iv) L. crispatus-pPG612-treatment group (LG, n = 45), where uteri were treated with 95% alcohol on the third day of oestrus and 0.1 ml × 108 CFU/ml L. crispatus-pPG612-G-CSF on the sixth day of oestrus via intrauterine injection; (v) G-CSF-treatment group (G, n = 52), where uteri were treated with 95% alcohol on the third day of oestrus and 30 µg/kg G-CSF on the sixth day of oestrus via intrauterine injection. Then, we compared the effects of L. crispastus, L. crispatus-pPG612-G-CSF and G-CSF on endometrial thickness, angiogenesis, fibrosis, and inflammation in the TE mouse.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We collected uterine tissues for haematoxylin-eosin staining, immunohistochemical staining, Western blot and RT-PCR, as well as serum for ELISA and uterine flushing solution for high-throughput sequencing.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared with those in the M group (the mice of the group were intrauterine injected 95% alcohol and treated with saline solution), the L. crispatus-pPG612-G-CSF strain increased the thickness of the endometrium (P < 0.001) and the number of blood vessels and glands (both P < 0.001), enhanced the expression of cytokeratin 19 (CK19) (P < 0.001), vimentin (Vim) (P < 0.001), vascular endothelial growth factor-A (P < 0.001), and CD34 (P < 0.001), and decreased fibrosis levels (P = 0.004). In addition, the high-throughput sequencing results indicated that the L. crispatus-pPG612-G-CSF strain could decrease the abundance of Pseudomonas (P = 0.044) and Actinomyces spp. (P = 0.094) in TE mice and increased the average number of embryos (P = 0.036). Finally, the L. crispatus-pPG612-G-CSF strain was preliminarily confirmed to activate the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) signalling pathway and enhance the mRNA expression of hypoxia-inducible factor-1α (P < 0.001), vascular endometrial growth factor (P = 0.003), and endothelial cell nitric oxide synthase (P = 0.003) in mouse uterine tissue.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Therapy with the L. crispatus-pPG612-G-CSF strain has tremendous potential to accelerate the reparative processes of TE. However, we have reported only the expression of genes and proteins related to the PI3K/AKT pathway, and numerous other mechanisms may also be involved in the restoration of the endometrium by L. crispatus-pPG612-G-CSF.

WIDER IMPLICATIONS OF THE FINDINGS

The results from the study provide new ideas and suggest new methods for TE treatment.

STUDY FUNDING/COMPETING INTEREST(S)

This work was financially supported by the Project of Science and Technology Development Plan of Jilin Province (grant number 20210101232JC), the Science and Technology Plan Item of Jilin Provincial Education Department (grant number JT53101022010), and the Doctoral Research Start-up Fund of Jilin Medical University (grant numbers JYBS2021014LK and 2022JYBS006KJ). The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.

Evolution of biotechnological advances and regenerative therapies for endometrial disorders: a systematic review

BACKGROUND

The establishment and maintenance of pregnancy depend on endometrial competence. Asherman syndrome (AS) and intrauterine adhesions (IUA), or endometrial atrophy (EA) and thin endometrium (TE), can either originate autonomously or arise as a result from conditions (i.e. endometritis or congenital hypoplasia), or medical interventions (e.g. surgeries, hormonal therapies, uterine curettage or radiotherapy). Affected patients may present an altered or inadequate endometrial lining that hinders embryo implantation and increases the risk of poor pregnancy outcomes and miscarriage. In humans, AS/IUA and EA/TE are mainly treated with surgeries or pharmacotherapy, however the reported efficacy of these therapeutic approaches remains unclear. Thus, novel regenerative techniques utilizing stem cells, growth factors, or tissue engineering have emerged to improve reproductive outcomes.

OBJECTIVE AND RATIONALE

This review comprehensively summarizes the methodologies and outcomes of emerging biotechnologies (cellular, acellular, and bioengineering approaches) to treat human endometrial pathologies. Regenerative therapies derived from human tissues or blood which were studied in preclinical models (in vitro and in vivo) and clinical trials are discussed.

SEARCH METHODS

A systematic search of full-text articles available in PubMed and Embase was conducted to identify original peer-reviewed studies published in English between January 2000 and September 2023. The search terms included: human, uterus, endometrium, Asherman syndrome, intrauterine adhesions, endometrial atrophy, thin endometrium, endometritis, congenital hypoplasia, curettage, radiotherapy, regenerative therapy, bioengineering, stem cells, vesicles, platelet-rich plasma, biomaterials, microfluidic, bioprinting, organoids, hydrogel, scaffold, sheet, miRNA, sildenafil, nitroglycerine, aspirin, growth hormone, progesterone, and estrogen. Preclinical and clinical studies on cellular, acellular, and bioengineering strategies to repair or regenerate the human endometrium were included. Additional studies were identified through manual searches.

OUTCOMES

From a total of 4366 records identified, 164 studies (3.8%) were included for systematic review. Due to heterogeneity in the study design and measured outcome parameters in both preclinical and clinical studies, the findings were evaluated qualitatively and quantitatively without meta-analysis. Groups using stem cell-based treatments for endometrial pathologies commonly employed mesenchymal stem cells (MSCs) derived from the human bone marrow or umbilical cord. Alternatively, acellular therapies based on platelet-rich plasma (PRP) or extracellular vesicles are gaining popularity. These are accompanied by the emergence of bioengineering strategies based on extracellular matrix (ECM)-derived hydrogels or synthetic biosimilars that sustain local delivery of cells and growth factors, reporting promising results. Combined therapies that target multiple aspects of tissue repair and regeneration remain in preclinical testing but have shown translational value. This review highlights the myriad of therapeutic material sources, administration methods, and carriers that have been tested.

WIDER IMPLICATIONS

Therapies that promote endometrial proliferation, vascular development, and tissue repair may help restore endometrial function and, ultimately, fertility. Based on the existing evidence, cost, accessibility, and availability of the therapies, we propose the development of triple-hit regenerative strategies, potentially combining high-yield MSCs (e.g. from bone marrow or umbilical cord) with acellular treatments (PRP), possibly integrated in ECM hydrogels. Advances in biotechnologies together with insights from preclinical models will pave the way for developing personalized treatment regimens for patients with infertility-causing endometrial disorders such as AS/IUA, EA/TE, and endometritis.

REGISTRATION NUMBER

https://osf.io/th8yf/.

Comparative analysis of superovulated versus uterine-embryo synchronized recipients for embryo transfer in cynomolgus monkeys (Macaca fascicularis)

Introduction

Assisted reproductive technologies (ARTs), such as intracytoplasmic sperm injection and embryo transfer, are essential for generating genetically edited monkeys. Despite their importance, ARTs face challenges in recipient selection in terms of time and the number of animals required. The potential of superovulated monkeys, commonly used as oocyte donors, to serve as surrogate mothers, remains underexplored. The study aimed to compare the efficacy of superovulated and uterine-embryo synchronized recipients of embryo transfer in cynomolgus monkeys (Macaca fascicularis).

Methods

This study involved 23 cynomolgus monkeys divided into two groups-12 superovulated recipients and 11 synchronized recipients. The evaluation criteria included measuring endometrial thickness on the day of embryo transfer and calculating pregnancy and implantation rates to compare outcomes between groups.

Results

The study found no statistically significant differences in endometrial thickness (superovulated: 4.48 ± 1.36 mm, synchronized: 5.15 ± 1.58 mm), pregnancy rates (superovulated: 30.8%, synchronized: 41.7%), and implantation rates (superovulated: 14.3%, synchronized: 21.9%) between the groups (p > 0.05).

Conclusion

The observations indicate that superovulated recipients are as effective as synchronized recipients for embryo transfer in cynomolgus monkeys. This suggests that superovulated recipients can serve as viable options, offering an efficient and practical approach to facilitate the generation of gene-edited models in this species.

The impact of intracytoplasmic sperm injection versus conventional in vitro fertilization on the reproductive outcomes of couples with non-male factor infertility and frozen-thawed embryo transfer cycles

This study was aimed to investigate the impact of intracytoplasmic sperm injection (ICSI) on reproductive outcomes in couples with non-male factor infertility and frozen-thawed embryo transfer (FET) treatment. This retrospective cohort study involved a total of 10,143 cycles from 6206 couples who underwent FET at the Third Affiliated Hospital of Zhengzhou University between January 2016 and September 2022. Patients were categorized into two groups based on the insemination methods of transferred embryos. Clinical and neonatal outcomes were compared between ICSI and conventional in vitro fertilization (cIVF) groups. The results showed that ICSI was not associated with improved clinical outcomes compared to cIVF. However, ICSI was associated with lower birthweight when twins were born. In conclusion, although subgroup analysis showed that ICSI was associated with slightly improved live birth rate for infertile couples with non-male factor infertility compared to cIVF, the regression analysis showed that ICSI did not demonstrate any improvement of the reproductive outcomes. The infertile women with twin pregnancies should be further informed of the lower birthweight and lower birth length when their oocytes were inseminated with ICSI. The findings of this study provide valuable insights for clinicians when discussing the benefits and risks of ICSI in patients with non-male factor infertility.

Does it affect the live birth rates to have a maximum endometrial thickness of 7, 8, or 9 mm in in-vitro fertilization-embryo transfer cycles?

OBJECTIVE

To assess the effect of endometrial thickness (EMT) on live birth rates (LBR) in women with endometrial lining between 7.0-9.9 mm.

METHODS

This retrospective cohort study included women who underwent fresh and frozen embryo transfers between 2008 and 2018, grouped according to their maximum EMT; group 1, 7.0-7.9 mm; group 2, 8.0-8.9 mm; and group 3, 9.0-9.9 mm and underwent blastocyst transfer.

RESULTS

The study included 7,091 in-vitro fertilization cycles: 1,385 in group 1, 3,000 in group 2, and 2,706 in group 3. The combined LBR was 22.2%. The mean age of women at oocyte retrieval day was 36.7±4.5 years. There was no difference in female age at oocyte retrieval or in the quality of embryos transferred between the three groups. Group 1 had more diagnoses of diminished ovarian reserve (25.8% vs. 19.5% and 19.1%; p<0.001) and less male factor infertility compared with group 2 and 3, respectively (25.0% vs. 28.8% and 28.5%; P=0.024). LBR was higher with increasing endometrial thickness, group 2 vs. group 1 (22.0% vs. 17.4%; P=0.0004), group 3 vs. group 1 (25.0% vs. 17.2%; p<0.001), and group 3 vs. group 2 (25.0% vs. 22.0%; P=0.008). After controlling for confounding factors, these three groups did not differ in LBR (group 1 vs. group 2, odds ratio [OR], 1.08; 95% confidence interval [CI], 0.83-1.4; P=0.54 and group 1 vs. group 3, OR, 1.16; 95% CI, 0.90-1.51; P=0.24).

CONCLUSION

Live birth rates in women with endometrial thickness between 7.0-9.9 mm were not affected by different cut-offs when blastocyst transfer was performed.

Association between endometrial thickness and birthweight of singletons from vitrified-warmed cycles: a retrospective cohort study

RESEARCH QUESTION

What is the association between endometrial thickness (EMT) and the birthweight of singleton infants born from frozen-thawed embryo transfer cycles?

DESIGN

This retrospective cohort study was conducted from January 2016 to December 2019. Participants were categorized into a natural cycle (NC, n = 8132) group and hormone replacement therapy (HRT, n = 4975) group. Only singleton deliveries were included. The primary outcomes were measures of birthweight and relevant indexes. Multivariable logistic regression and multivariable-adjusted linear regression models that incorporated restricted cubic splines were used.

RESULTS

In the HRT group, the risk of delivering a small for gestational age (SGA) infant was increased in women with an EMT <8.0 mm (adjusted odds ratio [aOR] 1.85, 95% confidence interval [CI] 1.17-2.91) compared with women with an EMT of 8.0 to <12.0 mm, and increased with an EMT ≥12.0 mm (aOR 1.85, 95% CI 1.03-3.33). An inverted U-shaped relationship was found between EMT and birthweight in women with HRT. No significant differences were shown in birthweight z-score, or being SGA or large for gestational age, in singletons among the three EMT groups in the natural cycles.

CONCLUSIONS

A thinner endometrium seen in women undergoing HRT cycles was associated with a lower birthweight z-score, as well as a higher risk of SGA. However, no significant association was observed between EMT and birthweight z-score or SGA in the NC group. It is noteworthy that a thicker endometrium was not associated with a higher birthweight in frozen-thawed embryo transfer (FET) cycles. Women with a thin endometrium who achieve pregnancy require specialized attention, particularly if they are undergoing FET with HRT cycles.

Cytoskeletal and inter-cellular junction remodelling in endometrial organoids under oxygen-glucose deprivation: a new potential pathological mechanism for thin endometria

STUDY QUESTION

What is the pathological mechanism involved in a thin endometrium, particularly under ischaemic conditions?

SUMMARY ANSWER

Endometrial dysfunction in patients with thin endometrium primarily results from remodelling in cytoskeletons and cellular junctions of endometrial epithelial cells under ischemic conditions.

WHAT IS KNOWN ALREADY

A healthy endometrium is essential for successful embryo implantation and subsequent pregnancy; ischemic conditions in a thin endometrium compromise fertility outcomes.

STUDY DESIGN, SIZE, DURATION

We recruited 10 patients with thin endometrium and 15 patients with healthy endometrium. Doppler ultrasound and immunohistochemical results confirmed the presence of insufficient endometrial blood perfusion in patients with thin endometrium. Organoids were constructed using healthy endometrial tissue and cultured under oxygen-glucose deprivation (OGD) conditions for 24 h. The morphological, transcriptomic, protein expression, and signaling pathway changes in the OGD organoids were observed. These findings were validated in both thin endometrial tissue and healthy endometrial tissue samples.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Endometrial thickness and blood flow were measured during the late follicular phase using transvaginal Doppler ultrasound. Endometrial tissue was obtained via hysteroscopy. Fresh endometrial tissues were used for the generation and culture of human endometrial organoids. Organoids were cultured in an appropriate medium and subjected to OGD to simulate ischemic conditions. Apoptosis and cell death were assessed using Annexin-V/propidium iodide staining. Immunofluorescence analysis, RNA sequencing, western blotting, simple westerns, immunohistochemistry, and electron microscopy were conducted to evaluate cellular and molecular changes.

MAIN RESULTS AND THE ROLE OF CHANCE

Patients with thin endometrium showed significantly reduced endometrial thickness and altered blood flow patterns compared to those with healthy endometrium. Immunohistochemical staining revealed fewer CD34-positive blood vessels and glands in the thin endometrium group. Organoids cultured under OGD conditions exhibited significant morphological changes, increased apoptosis, and cell death. RNA-seq identified differentially expressed genes related to cytoskeletal remodeling and stress responses. OGD induced a strong cytoskeletal reorganization, mediated by the RhoA/ROCK signaling pathway. Additionally, electron microscopy indicated compromised epithelial integrity and abnormal cell junctions in thin endometrial tissues. Upregulation of hypoxia markers (HIF-1α and HIF-2α) and activation of the RhoA/ROCK pathway were also observed in thin endometrial tissues, suggesting ischemia and hypoxia as underlying mechanisms.

LARGE SCALE DATA

none.

LIMITATIONS AND REASONS FOR CAUTION

The study was conducted in an in vitro model, which may not fully replicate the complexity of in vivo conditions.

WIDER IMPLICATIONS OF THE FINDINGS

This research provides a new three-dimensional in vitro model of thin endometrium, as well as novel insights into the pathophysiological mechanisms of endometrial ischaemia in thin endometrium, offering potential avenues for identifying therapeutic targets for treating fertility issues related to thin endometrium.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Natural Science Foundation of China (81925013); National Key Research and Development Project of China (2022YFC2702500, 2021YFC2700303, 2021YFC2700601); the Capital Health Research and Development Project (SF2022-1-4092); the National Natural Science Foundation of China (82288102, 81925013, 82225019, 82192873); Special Project on Capital Clinical Diagnosis and Treatment Technology Research and Transformation Application (Z211100002921054); the Frontiers Medical Center, Tianfu Jincheng Laboratory Foundation(TFJC2023010001). The authors declare that no competing interests exist.

Impact of elevated serum estradiol levels before progesterone administration on pregnancy outcomes in frozen-thawed embryo transfer for hormone replacement therapy

OBJECTIVE

The objective of this retrospective cohort study is to investigate the impact of monitoring serum estradiol (E2) levels before progesterone administration within hormone replacement therapy (HRT) on pregnancy outcomes in women undergoing frozen-thawed embryo transfer (FET).

METHODS

Analyzed HRT-FET cycles conducted at a reproductive center from 2017 to 2022. Serum E2 levels were measured prior to progesterone administration. Multivariate stratified and logistic regression analyses were performed on 26,194 patients grouped according to terciles of serum E2 levels before progesterone administration.

RESULTS

The clinical pregnancy rate (CPR) and live birth rate (LBR) exhibited a gradual decline with increasing serum E2 levels across the three E2 groups. Even after controlling for potential confounders, including female age, body mass index, infertility diagnosis, cycle category, number of embryos transferred, fertilization method, indication for infertility, and endometrial thickness, both CPR and LBR persistently showed a gradual decrease as serum E2 levels increased within the three E2 groups. The same results were obtained by multivariate logistic regression analysis.

CONCLUSIONS

This large retrospective study indicates that elevated serum E2 levels before progesterone administration during HRT-FET cycles are associated with reduced CPR and LBR post-embryo transfer. Therefore, it is advisable to monitor serum E2 levels and adjust treatment strategies accordingly to maximize patient outcomes.

Clinical data-based modeling of IVF live birth outcome and its application

BACKGROUND

The low live birth rate and difficult decision-making of the in vitro fertilization (IVF) treatment regimen bring great trouble to patients and clinicians. Based on the retrospective clinical data of patients undergoing the IVF cycle, this study aims to establish classification models for predicting live birth outcome (LBO) with machine learning methods.

METHODS

The historical data of a total of 1405 patients undergoing IVF cycle were first collected and then analyzed by univariate and multivariate analysis. The statistically significant factors were identified and taken as input to build the artificial neural network (ANN) model and supporting vector machine (SVM) model for predicting the LBO. By comparing the model performance, the one with better results was selected as the final prediction model and applied in real clinical applications.

RESULTS

Univariate and multivariate analysis shows that 7 factors were closely related to the LBO (with P < 0.05): Age, ovarian sensitivity index (OSI), controlled ovarian stimulation (COS) treatment regimen, Gn starting dose, endometrial thickness on human chorionic gonadotrophin (HCG) day, Progesterone (P) value on HCG day, and embryo transfer strategy. By taking the 7 factors as input, the ANN-based and SVM-based LBO models were established, yielding good prediction performance. Compared with the ANN model, the SVM model performs much better and was selected as the final model for the LBO prediction. In real clinical applications, the proposed ANN-based LBO model can predict the LBO with good performance and recommend the embryo transfer strategy of potential good LBO.

CONCLUSIONS

The proposed model involving all essential IVF treatment factors can accurately predict LBO. It can provide objective and scientific assistance to clinicians for customizing the IVF treatment strategy like the embryo transfer strategy.

Pregnancy and obstetric outcomes after fertility-sparing management of endometrial cancer and atypical hyperplasia: a multicentre cohort study

STUDY QUESTION

What are the pregnancy and obstetric outcomes in women with atypical hyperplasia (AH) or early-stage endometrial cancer (EC) managed conservatively for fertility preservation?

SUMMARY ANSWER

The study found a live birth rate of 62% in patients with AH or EC after conservative treatment, with higher level of labour induction, caesarean section, and post-partum haemorrhage.

WHAT IS KNOWN ALREADY

Fertility-sparing treatment is a viable option for women with AH or EC during childbearing years, but the outcomes of such treatments, especially regarding pregnancy and obstetrics, need further exploration.

STUDY DESIGN, SIZE, DURATION

This retrospective cohort study analysed data from January 2010 to October 2022, involving 269 patients from the French national register of patients with fertility-sparing management of AH/EC.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women above 18 years of age, previously diagnosed with AH/EC, and approved for fertility preservation were included. Patients were excluded if they were registered before 2010, if their treatment began <6 months before the study, or if no medical record on the pregnancy was available.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 95 pregnancies in 67 women were observed. Pregnancy was achieved using ART in 63 cases (66%) and the live birth rate was 62%, with early and late pregnancy loss at 26% and 5%, respectively. In the 59 cases resulting in a live birth, a full-term delivery occurred in 90% of cases; 36% of cases required labour induction and 39% of cases required a caesarean section. The most common maternal complications included gestational diabetes (17%) and post-partum haemorrhaging (20%). The average (±SD) birthweight was 3110 ± 736 g; there were no significant foetal malformations in the sample. No significant difference was found in pregnancy or obstetric outcomes between ART-obtained and spontaneous pregnancies. However, the incidence of induction of labour, caesarean section, and post-partum haemorrhage appears higher than in the general population.

LIMITATIONS, REASONS FOR CAUTION

The retrospective nature of the study may introduce bias, and the sample size might be insufficient for assessing rare obstetric complications.

WIDER IMPLICATIONS OF THE FINDINGS

This study offers valuable insights for healthcare providers to guide patients who received fertility-sparing treatments for AH/EC. These pregnancies can be successful and with an acceptable live birth rate, but they seem to be managed with caution, leading to possible tendency for more caesarean sections and labour inductions. No increase in adverse obstetric outcomes was observed, with the exception of suspicion of a higher risk of post-partum haemorrhaging, to be confirmed.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received for this study. There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Walking on thin endometrium

PURPOSE OF REVIEW

Endometrial thickness has been regarded a predictor of success in assisted reproductive technology cycles and it seems a common practice to cancel embryo transfer when it is below a cut-off. However, various cut-offs have been proposed without a causal relationship between endometrial thickness and embryo implantation being established, casting doubt on the current dogma.

RECENT FINDINGS

Methodological limitations of the available studies on endometrial thickness are increasingly recognized and better designed studies do not demonstrate a cut-off value which requires cancelling an embryo transfer.

SUMMARY

Endometrium is important for implantation and a healthy pregnancy; however, ultrasound measured thickness does not seem to be a good marker of endometrial function.

The impact of estradiol supplementation on endometrial thickness and intrauterine insemination outcomes

The impact of estrogen supplementation during the follicular/proliferative phase on the endometrial lining thickness (EMT) prior to intrauterine insemination (IUI) remains largely unstudied. Our study examined changes in EMT and rates of clinical pregnancy, miscarriage, and live birth for all patients who completed an IUI cycle at Stanford Fertility Center from 2017-2023 (n = 2281 cycles). Cycles with estradiol supplementation (n = 309) were compared to reference cycles without supplementation (n = 1972), with the reference cohort further categorized into cycles with a pre-ovulatory EMT of < 7 mm ("thin-lining", n = 536) and ≥ 7 mm ("normal-lining", n = 1436). The estradiol group had a statistically significant greater change in EMT from baseline to ovulation compared to the thin-lining reference groups (2.4 mm vs 1.9 mm, p < =0.0001). Similar rates of clinical pregnancy and live birth were observed. After adjusting for age, BMI, race/ethnicity, infertility diagnosis, and EMT at trigger, the estradiol cohort had a significantly increased odds of miscarriage versus the entire reference cohort (2.46, 95 % confidence interval [1.18, 5.14], p = 0.02). Thus, although estradiol supplementation had a statistically significant increase in EMT compared to IUI cycles with thin pre-ovulatory EMT (<7 mm), this change did not translate into improved IUI outcomes such as increased rates of clinical pregnancy and live birth or decreased rate of miscarriage. Our study suggests that supplemental estradiol does not appear to improve IUI outcomes.

A retrospective cohort study to examine factors affecting live birth after hysteroscopic treatment of intrauterine adhesions

OBJECTIVE

To evaluate independent factors that affect the chance of live birth (LB) after hysteroscopic adhesiolysis in patients with intrauterine adhesions.

DESIGN

Retrospective cohort study.

SETTING

Hysteroscopic center of Fuxing Hospital in Beijing, China.

PATIENT(S)

Patients diagnosed with Asherman syndrome between June 2020, and February 2022.

INTERVENTION(S)

Hysteroscopic adhesiolysis is followed by a second look hysteroscopy to assess the outcome and follow-up for a year.

MAIN OUTCOME MEASURE(S)

Live birth rate (LBR) without the use of assisted reproductive technologies at 12-month follow-up.

RESULT(S)

Of the 544 women included in the cohort, the pregnancy rate at the end of 1 year of follow-up was 47.6% (95% confidence interval [CI] 45.5%-49.7%), and the LBR was 41.0% (95% CI 38.9%-43.1%). Stepwise multiple logistic regression analysis identified three independent predictors of LB in decreasing order of significance: increase in menstrual flow after surgery (odds ratio [OR] 3.69, 95% CI 1.77-8.21), postoperative endometrial thickness in the midluteal phase (OR 1.53, 95% CI 1.31-1.80), and the severity of recurred adhesion at second-look hysteroscopy (OR 0.62, 95% CI 0.50-0.76). Among subjects with good independent prognostic factors, namely, increased menstrual flow after surgery, postoperative endometrial thickness in the midluteal phase >6 mm, and no or minimal recurrence of adhesions at second-look hysteroscopy, the LBR was 69.0% (95% CI 65.4%-72.6%). On the other hand, in women (n = 26) without any of the three good prognostic factors, none had a successful LB (0).

CONCLUSION(S)

Overall, the LBR after treatment for Asherman syndrome was 41.0%. The prognosis is dependent on three outcome measures after surgery, namely, improvement in menstrual flow, postoperative endometrial thickness, and the minimal degree of recurrent adhesions at second-look hysteroscopy.

New advances in the treatment of thin endometrium

Thin endometrium (TE) is defined as a mid-luteal endometrial thickness ≤7mm. TE can affect endometrial tolerance, leading to lower embryo implantation rates and clinical pregnancy rates, and is also associated with impaired outcomes from assisted reproductive treatment. Herein, we systematically review TE causes, mechanisms, and treatments. TE pathogenesis has multiple causes, with the endometrium becoming thinner with age under hormonal influence. In addition, uterine cavity factors are important, as the inflammatory environment may affect expressions of certain genes thereby inhibiting endometrial stromal cell proliferation and promoting apoptosis. Long-term oral contraceptive use or the use of ovulation-promoting drugs are also definite factors contributing to endometrial thinning. Other patients have primary factors, for which the clinical etiology remains unknown. The main therapeutic strategies available for TE are pharmacological (including hormonal and vasoactive drugs), regenerative medicine, intrauterine infusion of growth factor-granulocyte colony-stimulating factor, autologous platelet-rich plasma, and complementary alternative therapies (including traditional Chinese herbal medicine and acupuncture). However, the associated mechanisms of action are currently unclear. Clinical scholars have proposed various approaches to improve treatment outcomes in patients with TE, and are exploring the principles of efficacy, offering potentials for novel treatments. It is hoped that this will improve TE tolerance, increase embryo implantation rates, and help more couples with infertility with effective treatments.

Increasing Endometrial Thickness Beyond 8 mm Does Not Alter Clinical Pregnancy Rate After Single Euploid Embryo Transfer

The aim of this study was to investigate if variation in endometrial thickness affects clinical pregnancy and live birth rates among patients undergoing single euploid embryo transfer (SET). A retrospective review of IVF cycles performed at a single private fertility institution between 2015 and 2020 was performed. Patients with normal uterine anatomy undergoing their first SET of a euploid embryo undergoing their first cycle at the center were included, for a total of 796 cycles. Endometrial thickness was measured by transvaginal ultrasound following 10-14 days of estradiol exposure. Specific infertility diagnoses did not significantly impact endometrial lining thickness with means across diagnoses ranging from 9.3 to 11.0 mm. Endometrial thickness was grouped into five categories: < 8 mm, 8-10 mm, 10-13 mm, 13-15 mm, and ≥ 15 mm. Using 8-10 mm as the reference group, the odds ratio of live birth was 0.5, 1.22, 1.05, and 1.05 for < 8 mm, 10-13 mm, 13-15 mm, and ≥ 15 mm groups, respectively. Risk of first trimester miscarriage was equivalent across groups. There was a trend toward an increased rate of biochemical pregnancies in patients with a < 8 mm and ≥ 15 mm endometrium; however, this was not statistically significant. The clinical pregnancy and live birth rate were lowest in patients with < 8-mm endometrial thickness. For single euploid embryo transfers, an endometrial lining greater than or equal to 8 mm confers optimal live birth rates following a medicated FET cycle. These data confirm the findings of prior studies in fresh embryo transfers without the confounders of supraphysiologic ovarian hormone concentrations and genetically untested embryos.

Luteal phase support in assisted reproductive technology

Infertility affects one in six couples, with in vitro fertilization (IVF) offering many the chance of conception. Compared to the solitary oocyte produced during the natural menstrual cycle, the supraphysiological ovarian stimulation needed to produce multiple oocytes during IVF results in a dysfunctional luteal phase that can be insufficient to support implantation and maintain pregnancy. Consequently, hormonal supplementation with luteal phase support, principally exogenous progesterone, is used to optimize pregnancy rates; however, luteal phase support remains largely 'black-box' with insufficient clarity regarding the optimal timing, dosing, route and duration of treatment. Herein, we review the evidence on luteal phase support and highlight remaining uncertainties and future research directions. Specifically, we outline the physiological luteal phase, which is regulated by progesterone from the corpus luteum, and evaluate how it is altered by the supraphysiological ovarian stimulation used during IVF. Additionally, we describe the effects of the hormonal triggers used to mature oocytes on the degree of luteal phase support required. We explain the histological transformation of the endometrium during the luteal phase and evaluate markers of endometrial receptivity that attempt to identify the 'window of implantation'. We also cover progesterone receptor signalling, circulating progesterone levels associated with implantation, and the pharmacokinetics of available progesterone formulations to inform the design of luteal phase support regimens.

The influence of radical trachelectomy on endometrial thickness in in vitro fertilization-embryo transfer

AIM

Both morbidity and mortality rates of cervical cancer are increasing, especially in reproductive-aged women. Radical trachelectomy (RT) is an effective fertility-preserving surgery for early-stage cervical cancer. This study aimed to determine the influence of RT on endometrial thickness during in vitro fertilization-embryo transfer (IVF-ET).

METHODS

Forty-four patients had undergone RT, and 23 women undergoing IVF-ET treatment (105 ET cycles) were included. Endometrial thickness during hormone replacement therapy (HRT) was retrospectively evaluated and compared between patients with and without RT.

RESULTS

Eleven patients (50 ET cycles) in the RT group and 12 (52 ET cycles) in the control group were investigated. Compared with the control group, higher ET cancellation rates were observed in patients in the RT group (1 of 52 cycles [control group] vs. 8 of 50 cycles [RT group], p < 0.01). Endometrial thinning was not affected by patient age at first IVF-ET treatment, history of artificial abortion, preservation of uterine arteries during RT, or postoperative chemotherapy (p = 0.27, 1, 1, and 1, respectively).

CONCLUSIONS

Our data revealed that RT influenced endometrial thickness in IVF-ET. This was not affected by the background of the patients or perioperative management in this study. We could not reveal the underlying mechanism, but it is postulated that the transient postoperative uterine blood flow status and postoperative infections may have some effect on the endometrium. To resolve these issues, accumulation of evidences are required. We recommend informing patients about the impact of RT on IVF-ET before starting assisted reproductive technology (ART).

Platelet-rich plasma infusion as an adjunct treatment for persistent thin lining in frozen embryo transfer cycles: first US experience report

PURPOSE

To study effect of intrauterine infusion of platelet-rich plasma (PRP) on endometrial growth in the setting of thin endometrial lining in patients with prior cancelled or failed frozen embryo transfer (FET) cycles.

MATERIALS AND METHODS

Single-arm cohort study of forty-six patients (51 cycles) with endometrial lining thickness (EMT) < 6 mm in prior cancelled or failed FET cycles requesting intrauterine PRP treatment in upcoming FET cycle. The primary outcomes were final EMT in FET cycle and change in EMT after PRP. The secondary outcomes were overall pregnancy rate, clinical pregnancy rate, miscarriage rate, ongoing pregnancy, and live birth rates.

RESULTS

The mean pre-PRP EMT in all FET cycles was 4.0 ± 1.1 mm, and mean post-PRP EMT (final) was 7.1 ± 1.0 mm. Of 51 cycles, 33 (64.7%) reached ≥ 7 mm after PRP administration. There was a significant difference between pre-PRP EMT and post-PRP EMT in all FET cycles, with mean difference of 3.0 ± 1.5 mm. Three cycles were cancelled for failure to reach adequate lining. Total pregnancy rate was 72.9% in our cohort of 48 cycles that proceeded to transfer. Clinical pregnancy rate was 54.2% (26/48 FET cycles); clinical miscarriage rate was 14.3% (5/35 pregnancies). Twenty six women had live birth (18 with EMT ≥ 7 mm and 8 with EMT < 7 mm). Response to PRP was not correlated with any pre-cycle characteristics.

CONCLUSION

We demonstrate a significant improvement in lining thickness and pregnancy rates in this challenging cohort of women after PRP infusion, with no adverse events. Cost-effectiveness of PRP with benefits and alternatives should be carefully considered.

The impact of previous conservative treatment of atypical hyperplasia on pregnancy outcomes after IVF/ICSI-embryo transfer: a propensity score-matched retrospective cohort study

STUDY QUESTION

Do women have worse pregnancy and neonatal outcomes of IVF/ICSI-fresh embryo transfer (ET) after conservative treatment of atypical hyperplasia (AH)?

SUMMARY ANSWER

AH has no impact on live birth but is associated with increased risks of pregnancy loss and preterm delivery (PTD).

WHAT IS KNOWN ALREADY

AH is a precancerous lesion of endometrial cancer. Several recognized AH risk factors include nulliparity, increased body mass index, ovulation disorders, diabetes mellitus, and others. As such, patients are suggested to attempt conception upon achieving AH regression. Recently, successful pregnancies with IVF/ICSI have been increasingly reported.

STUDY DESIGN, SIZE, DURATION

Forty-two patients with AH regression and 18 700 women with no evidence of endometrial abnormality, who underwent their first autologous oocytes' retrieval and fresh ET cycles of IVF/ICSI in the Center for Reproductive Medicine, Shandong University, from May 2008 to July 2021, were retrospectively enrolled.

PARTICIPANTS/MATERIALS, SETTING, METHODS

First, 42 AH patients were propensity score matched with control women (n = 168) at a 1:4 ratio. Reproductive outcomes and maternal/neonatal complications were compared between the matched pairs. Binary logistic regression analyses were conducted to assess odds ratios (ORs) of AH for live birth, pregnancy loss, and PTD from AH women and all 18 700 eligible controls.

MAIN RESULT AND THE ROLE OF CHANCE

Patients with AH achieved a numerically lower live birth rate (LBR) as compared to the matched controls, but without significant difference (26% versus 37%, P = 0.192). However, compared with the matched controls, AH patients showed significantly higher rates of pregnancy loss (52% versus 21%, P = 0.003) and PTD (45% versus 16%, P = 0.041). Further analyses revealed a statistically significantly increased rate of late pregnancy loss (17% versus 3%, P = 0.023), but not early miscarriage (35% versus 18%, P = 0.086), in the AH group. Furthermore, after correcting for potential confounders, the likelihood of a live birth in AH patients narrowly failed to be statistically significantly different from controls (adjusted OR [aOR]: 0.51, 95% CI: 0.25-1.04, P = 0.064). Nonetheless, the logistic regression reconfirmed that AH was an independent risk factor for pregnancy loss (aOR: 3.62, 95% CI: 1.55-8.46, P = 0.003), late pregnancy loss (aOR: 9.33, 95% CI: 3.00-29.02, P < 0.001), and PTD (aOR: 5.70, 95% CI: 1.45-22.38, P = 0.013).

LIMITATIONS, REASONS FOR CAUTION

Selection bias was an inherent drawback of this study. First, because of the low AH prevalence among women receiving IVF/ICSI treatment, and consequently, limited sample size, the relationship between AH with LBR and adverse complications might be concealed and underestimated. Hence, the results should be interpreted cautiously. Similarly, the impacts of diverse clinical features of AH patients on the pregnancy outcomes need further studies in a larger population. Second, although most data used in this study were obtained by reviewing the medical records, missing data did exist and so did the recall bias. Third, although the propensity score matching and multivariable logistic models were performed collectively in order to minimize potential confounders between AH and controls, the intrinsic disadvantages of the retrospective nature of this study could not be avoided completely, and additional confirmation bias might be induced with reduplication of statistical analyses.

WIDER IMPLICATION OF THE FINDINGS

Our results highlight the necessity of adequate counseling and intensive pregnancy monitoring for AH individuals and their families.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from the National Key Research & Developmental Program of China (2022YFC2703800), the Natural Science Foundation of Shandong Province (ZR2022MH009), and Projects of Medical and Health Technology Development Program in Shandong Province (202005010520, 202005010523). There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Progress on the Endometrium

The endometrium is a dynamic tissue that facilitates mammalian internal reproduction and thus, the ability to deliver live born progeny that are more easily protected from predators. This tissue is unique in its ability to undergo cyclic regeneration and destruction in the absence of pregnancy. Ovarian steroids guide endometrial proliferation and maturation promoting its receptivity and selectivity with regards to blastocyst implantation. It is decidualization, terminal stromal maturation, that prevents the trophoblast from breeching containment of the uterus and allows for endometrial sloughing should pregnancy not occur. Endometrial pathology is highly variable and therefore a wide array of diagnostic measures are required for its interrogation. There remains no single test that can distinguish between all potential issues and it is critical that appropriate and evidence-based endometrial assessment is carried out. Emerging data on developmental markers, inflammatory mediators, and bacterial profiling offer hope that conditions including endometriosis, cancer, infertility, and implantation failure will be more easily and less invasively diagnosed. This will allow for a more timely and targeted approach to intervention. Accordingly, assessing novel measures requires an evidence-based approach prior to their mass utilization.

The effects of different endometrial preparation regimens on pregnancy outcomes in frozen-thawed embryo transfer cycles: a prospective randomized controlled study

OBJECTIVE

An increasing number of research have emerged to compare the pregnancy outcomes between the natural cycle and the hormone replacement therapy (HRT) cycle in preparing the endometrium for frozen-thawed embryo transfer (FET), but the results are controversial. This prospective randomized controlled study was hence designed to obtain more solid evidence.

MATERIALS AND METHODS

In this study, patients with regular menstrual cycle length (21-35 days) who underwent FET between January 2010 to December 2017 were recruited for this study. Upon further filtering with the selection criteria of patients being, a total of 405 patients were recruited and randomized. Finally, analysis was performed on 384 patients: 178 belonged to the natural cycle group whereas the remaining 206 were in the HRT group. The primary outcome was live birth rate, while the secondary outcomes were implantation rate, clinical pregnancy rate, early miscarriage rate, late miscarriage rate, multiple birth rate and low birth weight rate.

RESULTS

The live birth rate (37.6% vs 30.1%, p = 0.119) of natural cycle group were higher than those of the hormone replacement therapy group, although the difference was not significant. The secondary outcomes were not found to differ significantly between the two groups. Nonetheless, the endometrium was found to be thicker in the natural cycle group (10.75 mm) than the HRT group (9.00 mm) (p < 0.001).

CONCLUSION

No significant differences were observed between the pregnancy outcomes of the natural cycle group and the HRT group which comprised of patients with regular menstrual cycle length.

Does endometrial compaction before embryo transfer affect pregnancy outcomes? a systematic review and meta-analysis

Objective

There is no clear evidence of clinical significance of endometrial compaction, which can be measured by a reduction in endometrial thickness (EMT) during the follicular-luteal transition before the day of embryo transfer. In this study, we aim to determine whether endometrial compaction has an effect on in vitro fertilization (IVF) success.

Methods

We searched PubMed, Cochrane, Embase, and Web of Science electronic databases for studies published in English up to March 2023. Heterogeneity between studies was assessed using the I2 statistic. The random effects model and fixed effects model was used to pool the risk ratio (RR) with a corresponding 95% confidence interval (CI). A subgroup analysis was performed based on different methods of ultrasonic measurement and different endometrial compaction rates (ECR). Stata 17.0 software was used for meta-analysis. Pregnancy outcomes, which included clinical pregnancy rate, ongoing pregnancy rate, live birth rate, and spontaneous abortion rate, were evaluated.

Results

In this study, 18 cohort studies were included, involving 16,164 embryo transfer cycles. Pooled results indicated that there was no significant difference between the endometrial compaction group and the non-compaction group in terms of clinical pregnancy rate (RR [95% CI]=0.98 [0.90,1.08]; I2 = 69.76%), ongoing pregnancy rate (RR [95% CI]=1.18 [0.95,1.47]; I2 = 78.77%), live birth rate (RR [95% CI]= 0.97 [0.92,1.02]; I2 = 0.00%) or spontaneous abortion rate (RR [95% CI]= 1.07[0.97,1.26]; I2 = 0.00%). According to the subgroup analysis of ultrasonic measurement methods, in the transvaginal ultrasound (TVUS) combined with abdominal ultrasonography (AUS) cycles of the endometrial compaction group, the rate of ongoing pregnancy (RR [95% CI] = 1.69 [1.26, 2.26]; I2 = 29.27%) and live birth (RR [95% CI] = 1.27 [1.00,1.61]; I2 = 62.28%) was significantly higher than that of the non-compaction group. Additionally, subgroup analysis based on ECR revealed a significantly higher rate of ongoing pregnancy when ECR ≥ 15% (RR [95% CI] = 1.99 [1.61, 2.47]; I2 = 0.00%).

Conclusion

Endometrial compaction has no adverse effect on clinical pregnancy rate, ongoing pregnancy rate, live birth rate, or spontaneous abortion rate. A possible explanation for the contradictory findings of previous studies lies in the method by which the EMT is measured.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023430511, identifier CRD42023430511.

Impact of letrozole co-treatment during ovarian stimulation on oocyte yield, embryo development, and live birth rate in women with normal ovarian reserve: secondary outcomes from the RIOT trial

STUDY QUESTION

Does letrozole (LZ) co-treatment during ovarian stimulation with gonadotropins for in IVF impact follicle recruitment, oocyte number and quality, embryo quality, or live birth rate (LBR)?

SUMMARY ANSWER

No impact of LZ was found in follicle recruitment, number of oocytes, quality of embryos, or LBR.

WHAT IS KNOWN ALREADY

Multi-follicle stimulation for IVF produces supra-physiological oestradiol levels. LZ is an aromatase inhibitor that lowers serum oestradiol thus reducing negative feedback and increasing the endogenous gonadotropins in both the follicular and the luteal phases, effectively normalizing the endocrine milieu during IVF treatment.

STUDY DESIGN, SIZE, DURATION

Secondary outcomes from a randomized, double-blind placebo-controlled trial (RCT) investigating once-daily 5 mg LZ or placebo during stimulation for IVF with FSH. The RCT was conducted at four fertility clinics at University Hospitals in Denmark from August 2016 to November 2018 and pregnancy outcomes of frozen-thawed embryo transfers (FET) registered until May 2023.

PARTICIPANTS/MATERIALS, SETTING, METHODS

One hundred fifty-nine women with expected normal ovarian reserve (anti-Müllerian hormone 8-32 nmol/l) were randomized to either co-treatment with LZ (n = 80) or placebo (n = 79). In total 1268 oocytes were aspirated developing into 386 embryos, and morphology and morphokinetics were assessed. One hundred twenty-nine embryos were transferred in the fresh cycle and 158 embryos in a subsequent FET cycle. The effect of LZ on cumulative clinical pregnancy rate (CPR), LBR, endometrial thickness in the fresh cycle, and total FSH consumption was reported.

MAIN RESULTS AND THE ROLE OF CHANCE

The proportion of usable embryos of retrieved oocytes was similar in the LZ group and the placebo group with 0.31 vs 0.36 (mean difference (MD) -0.05, 95% CI (-0.12; 0.03), P = 0.65). The size and number of aspirated follicles at oocyte retrieval were similar with 11.8 vs 10.3 follicles per patient (MD 1.5, 95% CI (-0.5; 3.1), P = 0.50), as well as the number of retrieved oocytes with 8.0 vs 7.9 oocytes (MD 0.1, 95% CI (-1.4; 1.6), P = 0.39) in the LZ and placebo groups, respectively. The chance of retrieving an oocyte from the 13 to 16 mm follicles at trigger day was 66% higher (95% CI (24%; 108%), P = 0.002) in the placebo group than in the LZ group, whilst the chance of retrieving an oocyte from the ≥17 mm follicles at trigger day was 50% higher (95% CI (2%; 98%), P = 0.04) in the LZ group than in the placebo group. The proportion of fertilized oocytes with two-pronuclei per retrieved oocytes or per metaphase II oocytes (MII) (the 2PN rates) were similar regardless of fertilization with IVF or ICSI with 0.48 vs 0.57 (MD -0.09, 95% CI (-0.24; 0.04), P = 0.51), and 0.62 vs 0.64 (MD -0.02, 95% CI (-0.13; 0.07), P = 0.78) in the LZ and placebo groups, respectively. However, the MII rate in the ICSI group was significantly lower with 0.75 vs 0.88 in the LZ vs the placebo group (MD -0.14, 95% CI (-0.22; -0.06), P = 0.03). Blastocysts on Day 5 per patient were similar with 1.5 vs 2.0, P = 0.52, as well as vitrified blastocysts per patient Day 5 with 0.8 vs 1.2 in (MD -0.4, 95% CI (-1.0; 0.2), P = 0.52) and vitrified blastocysts per patient Day 6 with 0.6 vs 0.6 (MD 0, 95% CI (-0.3; 0.3), P = 1.00) in the LZ vs placebo group, respectively. Morphologic evaluation of all usable embryos showed a similar distribution in 'Good', 'Fair', and 'Poor', in the LZ vs placebo group, with an odds ratio (OR) of 0.8 95% CI (0.5; 1.3), P = 0.68 of developing a better class embryo. Two hundred and ninety-five of the 386 embryos were cultured in an embryoscope. Morphokinetic annotations showed that the odds of having a high KIDscore™ D3 Day 3 were 1.2 times higher (CI (0.8; 1.9), P = 0.68) in the LZ group vs the placebo group. The CPR per transfer was comparable with 31% vs 39% (risk-difference of 8%, 95% CI (-25%; 11%), P = 0.65) in the LZ and placebo group, respectively, as well as CPR per transfer adjusted for day of transfer, oestradiol and progesterone levels at trigger, progesterone levels mid-luteal, and number of oocytes retrieved (adjusted OR) of 0.8 (95% CI (0.4; 1.6), P = 0.72). Comparable LBR were found per transfer 28% vs 37% (MD -9%, 95% CI (-26%; 9%), P = 0.60) and per randomized women 24% vs 30% (MD of -6%, CI (-22%; 8%), P = 0.60) in the LZ group and placebo group, respectively. Furthermore, 4.8 years since the last oocyte aspiration, a total of 287 of 386 embryos have been transferred in the fresh or a subsequently FET cycle, disclosing the cumulative CPR, which is similar with 38% vs 34% (MD 95% CI (8%; 16%), P = 0.70) in the LZ vs placebo group.

LIMITATIONS, REASONS FOR CAUTION

Both cleavage stage and blastocyst transfer and vitrification were permitted in the protocol, making it necessary to categorize their quality and pool the results. The study was powered to detect hormonal variation but not embryo or pregnancy outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

The similar utilization rate and quality of the embryos support the use of LZ co-treatment for IVF with specific indication as fertility preservation, patients with previous cancer, or poor responders. The effect of LZ on mature oocytes from different follicle sizes and LBRs should be evaluated in a meta-analysis or a larger RCT.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was received from EU Interreg for ReproUnion, Sjaelland University Hospital, Denmark, Ferring Pharmaceuticals, and Gedeon Ricther. Roche Diagnostics contributed with assays. A.P. has received grants from Ferring, Merck Serono, and Gedeon Richter, consulting fees from Preglem, Novo Nordisk, Ferring, Gedeon Richter, Cryos, & Merck A/S, speakers fees from Gedeon Richter, Ferring, Merck A/S, Theramex, & Organon, and travel support from Gedeon Richter. The remaining authors declare that they have no competing interests in the research or publication.

TRIAL REGISTRATION NUMBERS

NCT02939898 and NCT02946684.

Can endometrial compaction predict live birth rates in assisted reproductive technology cycles? A systematic review and meta-analysis

PURPOSE

Endometrial compaction (EC) is defined as the difference in endometrial thickness from the end of the follicular phase to the day of embryo transfer (ET). We aimed to determine the role of EC in predicting assisted reproductive technology (ART) success by conducting a meta-analysis of studies reporting the association between EC and clinical outcomes of ART.

METHODS

MEDLINE via PubMed, Web of Science, Scopus, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched from the date of inception to May 19, 2023. The primary outcome was live birth rate (LBR) per ET. Secondary outcomes were live birth or ongoing pregnancy per ET, ongoing pregnancy per ET, clinical pregnancy per ET, and miscarriage per clinical pregnancy.

RESULTS

Fifteen studies were included. When data from all studies reporting live birth were pooled, overall LBR rates were comparable in cycles showing EC or not [RR = 0.97, 95%CI = 0.92 to 1.02; 10 studies, 11,710 transfer cycles]. In a subgroup of studies that included euploid ET cycles, a similar LBR for patients with and without EC was noted [RR = 0.99, 95%CI = 0.86 to 1.13, 4 studies, 1172 cycles]. The miscarriage rate did not seem to be affected by the presence or absence of EC [RR = 1.06, 95%CI = 0.90 to 1.24; 12 studies].

CONCLUSION

The predictive value of EC in determining LBR is limited, and assessment of EC may no longer be necessary, given these findings.

TRIAL REGISTRATION

PROSPERO CRD42023410389.

Novel predictors for livebirth delivery rate in patients with idiopathic non-obstructive azoospermia based on the clinical prediction model

Objective

To build a prediction model for live birth delivery per intracytoplasmic sperm injection (ICSI) in iNOA patients by obtaining sperm by microdissection testicular sperm extraction (mTESE).

Methods

A retrospective cohort study of 377 couples with iNOA male partners treated with 519 mTESE-ICSI cycles was conducted from September 2013 to July 2021 at the Reproductive Medical Centre of Peking University Third Hospital. Following exclusions, 377 couples with iNOA male partners treated with 482 mTESE-ICSIs were included. A prediction model for live birth delivery per ICSI cycle was built by multivariable logistic regression and selected by 10-fold cross-validation. Discrimination was evaluated by c-statistics and calibration was evaluated by the calibration slope.

Results

The live birth delivery rate per mTESE-ICSI cycle was 39.21% (189/482) in these couples. The model identified that the presence of motile sperm during mTESE, bigger testes, higher endometrial thickness on the day of human chorionic gonadotrophin (hCG) administration (ET-hCG), and higher quality embryos are associated with higher live birth delivery success rates. The results of the model were exported based on 10-fold cross-validation. In addition, the area under the mean ROC curve was 0.71 ± 0.05 after 10-fold cross-validation, indicating that the prediction model had certain prediction precision. A calibration plot with an estimated intercept of -1.653 (95% CI: -13.403 to 10.096) and a slope of 1.043 (95% CI: 0.777 to 1.308) indicated that the model was well-calibrated.

Conclusion

Our prediction model will provide valuable information about the chances of live birth delivery in couples with iNOA male partners who have a plan for mTESE-ICSI treatment. Therefore, it can improve and personalize counseling for the medical treatment of these patients.

Current perspectives on endometrial receptivity: A comprehensive overview of etiology and treatment

Recurrent implantation failure (RIF) remains a challenging problem in assisted reproductive technology (ART). Further insights into uterine abnormalities that can disturb embryo implantation should be obtained. This review provides an overview of the effects of organic and non-organic uterine disorders on endometrial receptivity. The results suggest that various uterine pathologies can lead to defective embryo implantation via multiple mechanisms. In particular, uterine adenomyosis dysregulates molecular and cellular interactions that are vital for successful embryo implantation with a background of chronic inflammation, which may be alleviated by pretreatment with a gonadotropin-releasing hormone agonist. Uterine myomas can cause endometrial deformation and adverse alterations in uterine contractility. Nonetheless, the effectiveness of myomectomy remains debated, and endometrial polyp removal may be considered, particularly in patients with RIF. Chronic endometritis abrogates the appropriate uterine immunological environment critical for embryo implantation. Abnormal endometrial microbiota have been suggested to influence endometrial receptivity; however, supporting evidence is currently scarce. Platelet-rich plasma therapy may be a potential treatment for thin endometria; nevertheless, further validation is required. Endometrial receptivity analysis can detect dysregulation of the window of implantation, and new non-invasive methods for predicting endometrial receptivity have recently been proposed. However, numerous issues still need to be fully clarified. Further clinical and basic studies are necessary to investigate the pathophysiology of defective endometrial receptivity and identify optimal treatments for patients undergoing ART, especially those with RIF.

A critical appraisal of studies on endometrial thickness and embryo transfer outcome

A receptive endometrium is required for successful embryo implantation. Endometrial thickness, as measured by ultrasonography, is the most commonly used marker of endometrial receptivity in assisted reproductive technology cycles. Several factors simultaneously affect both endometrial thickness and probability of live birth, including age, oestradiol concentration and oocyte number, among others. Most of the studies investigating a relationship between endometrial thickness and embryo transfer outcomes are retrospective and do not adequately address confounding factors, in addition to other limitations. Despite multiple meta-analyses and studies with large numbers of cycles, controversy still exists. The difference between the results from prospective and retrospective studies is also striking. This article presents a critical appraisal of the studies on endometrial thickness and embryo transfer outcomes in order to highlight methodological issues and how they can be overcome in future studies. Currently available evidence does not seem to support a modification of management just because endometrial thickness is below an arbitrary threshold.

Human endometrium-derived mesenchymal stem/stromal cells application in endometrial-factor induced infertility

Endometrial-factor induced infertility remains one of the most significant pathology among all fertility disorders. Stem cell-based therapy is considered to be the next-generation approach. However, there are still issues about successfully retrieving human endometrium-derived mesenchymal stem/stromal cells (hEnMSCs). Moreover, we need to establish a better understanding of the effect of hEnMSCs on the endometrial recovery and the clinical outcome. According to these challenges we created a multi-step study. Endometrium samples were collected from females undergoing assisted reproductive technology (ART) procedure due to couple infertility. These samples were obtained using an endometrium scratching. The hEnMSCs were isolated from endometrium samples and characterized with flow cytometry analysis. Groups of endometrium injured female mice were established by the mechanical injury to uterine horns and the intraperitoneal chemotherapy. The hEnMSCs suspension was injected to some of the studied female mice at approved time intervals. Histological changes of mice uterine horns were evaluated after Masson's trichrome original staining, hematoxylin and eosin (H&E) staining. The fertility assessment of mice was performed by counting formed embryo implantation sites (ISs). The expression of fibrosis related genes (Col1a1, Col3a1, Acta2, and CD44) was evaluated by the reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Results showed that endometrium scratching is an effective procedure for mesenchymal stem/stromal cells (MSCs) collection from human endometrium. Isolated hEnMSCs met the criteria for defining MSCs. Moreover, hEnMSCs-based therapy had a demonstrably positive effect on the repair of damaged uterine horns, including a reduction of fibrosis, intensity of inflammatory cells such as lymphocytes and polymorphonuclear cells (PMNs) and the number of apoptotic bodies. The injured mice which recieved hEnMSCs had higher fertility in comparison to the untreated mice. Gene expression was reflected in histology changes and outcomes of conception. In conclusion, hEnMSCs demonstrated a positive impact on endometrium restoration and outcomes of endometrial-factor induced infertility. Further exploration is required in order to continue exploring the multifactorial associations between stem cell therapy, gene expression, endometrial changes and reproductive health, so we can identify individually effective and safe treatment strategies for endometrial-factor induced infertility, which is caused by mechanical effect or chemotherapy, in daily clinical practise.

Reproductive history does not compromise subsequent live birth and perinatal outcome following in-vitro fertilization: analysis of 25 329 first frozen-thawed embryo transfer cycles without preimplantation genetic testing for aneuploidy

OBJECTIVE

To investigate the effect of women's reproductive history on live-birth rate and perinatal outcome after first frozen-thawed embryo transfer (FET) without preimplantation genetic testing for aneuploidy.

METHODS

This was a retrospective cohort study of women who had undergone their first FET cycle between January 2014 and December 2020 at a university-affiliated fertility center. No transferred embryo underwent preimplantation genetic testing for aneuploidy. The women were categorized into five groups based on their reproductive history: no previous pregnancy; previous termination of pregnancy (TOP); previous pregnancy loss; previous ectopic pregnancy (EP); and previous live birth. The women with no previous pregnancy were considered as the reference group. The primary outcome was the live-birth rate and secondary endpoints included rates of positive pregnancy test, clinical pregnancy, pregnancy loss and EP as well as perinatal outcomes such as birth weight and preterm birth. Multivariable logistic regression analyses were used to control for a number of potential confounders, including age, body mass index, education level, duration and cause of infertility, insemination method, type of endometrial preparation, number of embryos transferred, embryo developmental stage, quality of the embryos transferred, year of treatment and endometrial thickness. Additionally, propensity score matching (PSM) was used to check the robustness of the main findings.

RESULTS

In total, 25 329 women were included in the final analysis. On univariate analysis, each reproductive-history type except for previous EP was significantly associated with worse pregnancy outcome following in-vitro fertilization (IVF), including rates of positive pregnancy test, clinical pregnancy, pregnancy loss and live birth, when compared with the group of women with no previous pregnancy. However, after correcting for several potential confounders, the differences in rates of live birth, pregnancy loss, positive pregnancy test and clinical pregnancy were no longer significant between the study and control groups on multivariable regression models, while the risk of EP after embryo transfer was elevated among women with a previous TOP or EP. There was no increased risk of adverse perinatal outcome associated with reproductive history compared with the control group. Notably, similar results were obtained from the PSM models, confirming the robustness of the main findings.

CONCLUSION

Relative to women without a previous pregnancy, those with a prior TOP, pregnancy loss, EP or live birth did not have compromised live-birth rate or perinatal outcomes following FET without preimplantation genetic testing for aneuploidy, with the exception of an increased risk of EP in those with prior TOP or EP. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Effect of the endometrial thickness on the live birth rate: insights from 959 single euploid frozen embryo transfers without a cutoff for thickness

OBJECTIVE

To investigate whether endometrial thickness (ET) independently affects the live birth rate (LBR) after embryo transfer.

DESIGN

Retrospective study.

SETTING

Private assisted reproductive technology center.

PATIENT(S)

A total of 959 single euploid frozen embryo transfers.

INTERVENTION(S)

Vitrified euploid blastocyst transfer.

MAIN OUTCOME MEASURE(S)

Live birth rate per embryo transfer.

RESULT(S)

The conditional density plots did not demonstrate either a linear relationship between the ET and LBR or a threshold below which the LBR decreased perceivably. Receiver operating characteristic curve analyses did not suggest a predictive value of the ET for the LBR. The area under the curve values were 0.55, 0.54, and 0.54 in the overall, programmed, and natural cycle transfers, respectively. Logistic regression analyses with age, embryo quality, day of trophectoderm biopsy, body mass index, and ET did not suggest an independent effect of the ET on the LBR.

CONCLUSION(S)

We did not identify a threshold of the ET that either precluded live birth or under which the LBR decreases perceivably. Common practice of cancelling embryo transfers when the ET is <7 mm may not be justified. Prospective studies, in which the management of the transfer cycle would not be altered by ET, would provide higher-quality evidence on the subject.

Treatment options for endometrial hypoproliferation

PURPOSE OF REVIEW

Endometrial hypoproliferation refers to the failure of the endometrium to reach optimal thickness during fresh or frozen embryo transfer cycles in women undergoing infertility treatment with in-vitro fertilization (IVF). This review discusses the treatment options for endometrial hypoproliferation.

RECENT FINDINGS

Apart from factors related to the embryo quality, ultrasonographic findings associated with the endometrium, such as endometrial thickness, endometrial pattern and subendometrial blood flow, are considered key factors associated with the outcome of assisted reproductive treatment. To date, a consensus has not been reached regarding the definition of thin endometrium, while thresholds of 6, 7 or 8 mm have been used in the literature. Strategies to increase endometrial thickness can be reviewed in three groups: endocrine approaches, vitamins & supplements, and new experimental therapeutic interventions. Some of the recently introduced experimental therapeutic interventions such as platelet-rich plasma injection, stem cell treatment and tissue bioengineering are exciting potential therapies that need to be further studied.

SUMMARY

Despite a large number of publications on the topic, diagnosing and treating endometrial hypoproliferation remains a challenge. Well designed studies are needed to establish a widely accepted endometrial thickness cut-off value below which endometrial hypoproliferation is diagnosed and to generate meaningful data that would allow an evidence-based discussion of available therapeutic options with patients.

Personalized regenerative strategies and molecular diagnosis for in vitro fertilization success: a case report

Limited options are available for infertility associated with damaged or suboptimal tissues, typically the endometrium or ovaries. The goal of regenerative medicine is to restore function to specific tissues. Here, a 35-year-old female patient underwent two interventions of regenerative medicine: (i) autologous mesenchymal stem cells (MSCs) were applied in the myometrium, and (ii) intraovarian infusion of platelet-rich plasma (PRP). After two failed in vitro fertilization cycles (IVF), in which the endometrium was <5 mm, MSCs were applied, achieving a 7 mm trilaminar lining; however, the embryo quality remained poor. Therefore, intraovarian PRP was utilized for the next IVF cycle; the patient's response improved, and a euploid embryo developed. After the embryo transfer and a normal 38 weeks of pregnancy, a baby girl was born. Here, we demonstrate two forms of regenerative medicine that can be utilized to improve IVF.

Fibroblast growth factor 1 ameliorates thin endometrium in rats through activation of the autophagic pathway

Background: Thin endometrium is a reproductive disorder that affects embryo implantation. There are several therapies available for this disease, however they are not so effective. Fibroblast growth factor 1 (FGF1) is a member of fibroblast growth factor superfamily (FGFs), and it has been demonstrated that FGF1 expression was altered in samples collected from patients with thin endometrium. However, it is unclear if FGF1 could improve thin endometrium. The aim of this study was to investigate whether FGF1 have a therapeutic effect on thin endometrium. Methods: A model of thin endometrium induced by ethanol was constructed to investigate the effect and mechanism of action of FGF1 in thin endometrium. In the characterization experiments, 6-8 weeks female rats (n = 40) were divided into four groups: i) Control group; ii) Sham group; iii) Injured group; (iv) FGF1 therapy group. Endometrial tissues would be removed after three sexuel cycles after molding. Morphology and histology of the endometrium were evaluated by visual and hematoxylin and eosin staining. Masson staining and expression of α-SMA in endometrium showed the degree of endometrial fibrosis. Western blotting (PCNA、vWF and Vim) and immunohistochemistry (CK19 and MUC-1) demonstrated the effect of FGF1 on cell proliferation and angiogenesis. Moreover, immunohistochemistry (ER and PR) was used to explore the function of endometrium. The remaining rats (n = 36) were divided into three groups: i) Injured group; ii) FGF1 therapy group; and iii) 3-methyladenine. Western blotting (p38、p-p38、PI3K 、SQSTM1/p62、beclin-1 and LC3) was used to explore the mechanisms of FGF1. Results: In FGF1 therapy group, the morphology and histology of endometrium improved compared with the model group. Masson staining and the expression level of α-SMA showed that FGF1 could decrease the fibrotic area of endometrium. Besides, changes in ER and PR expression in the endometrium suggested that FGF1 could restore endometrium-related functions. Western blotting and immunohistochemistry revealed that PCNA, vWF, Vim, CK19 and MUC-1 were significantly increased after FGF1 treatment compared with the thin endometrium. In addition, Western blotting showed that p38, p-p38, PI3K, SQSTM1/p62, beclin-1 and LC3 levels were higher in FGF1 group than in the injured group. Conclusion: FGF1 application cured the thin endometrium caused by ethanol through autophagy mechanism.

The Cystic Anechoic Zone of Uterine Cavity Newly Observed during Controlled Ovarian Hyperstimulation Affects Pregnancy Outcomes of Fresh Embryo Transfer

During controlled ovarian hyperstimulation (COH), cystic anechoic zones in the uterine cavity are occasionally visible. This retrospective matched cohort study collected information on patients who underwent in vitro fertilization/intracytoplasmic injection (IVF/ICSI) from January 2014 to December 2020 at our center. The propensity score algorithm matched 179 cases that had uterine cystic anechoic zones, with 358 which did not have uterine cystic anechoic zones cases. After matching, the live birth rate (38.0% vs. 48.6%, p = 0.025) of patients with uterine cystic anechoic zones was lower than that in the no uterine cystic anechoic zone group, while for clinical pregnancy miscarriage rate (22.2% vs. 12.4%, p = 0.031), the rate was higher. The results showed no correlation in the association between live birth rate (r = −0.027, p = 0.718), clinical pregnancy rate (r = −0.037, p = 0.620) or biochemical pregnancy rate (r = −0.015, p = 0.840) and the diameters of the cystic anechoic zones in the uterine cavity. There was a significant difference in the type of endometrium between the two groups (p < 0.001). The result of this study can provide guidance to patients on whether to undergo fresh embryo transfer in the current cycle.

Thin endometrial lining: is it more prevalent in patients utilizing preimplantation genetic testing for monogenic disease (PGT-M) and related to prior hormonal contraceptive use?

STUDY QUESTION

Is a thin endometrial lining before ovulation triggering more prevalent in patients utilizing preimplantation genetic testing for monogenic disease (PGT-M) compared to the regular IVF/ICSI population and is this associated with prior hormonal contraceptive use?

SUMMARY ANSWER

Thin (<8 mm) endometrial lining is more prevalent in PGT-M patients compared to the regular IVF/ICSI population and is associated with both longer prior hormonal contraceptive use and a shorter cessation interval of hormonal contraceptives before IVF/ICSI treatment.

WHAT IS KNOWN ALREADY

Thin endometrial lining has been associated with lower pregnancy rates in IVF/ICSI cycles and increased chances of miscarriage and low birth weight. Endometrial thinning and atrophy occur during hormonal contraceptive use. Patients utilizing PGT-M typically use hormonal contraceptives up until treatment to avoid the risk of conception of a genetically affected child. Whether this could negatively affect endometrial thickness achieved during subsequent IVF/ICSI cycles is not known.

STUDY DESIGN, SIZE, DURATION

A retrospective case control study was performed, including all PGT-M patients attending the University Medical Centre Groningen (cases), between 2009 and 2018. The control group consisted of two non-PGT IVF/ICSI patients for each PGT-M patient, matched for age and treatment period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

First cycles of 122 PGT-M patients and 240 controls were included. Cessation interval of hormonal contraceptives was categorized as late cessation (cessation <1 year prior to treatment) or early cessation (>1 year prior to treatment). Endometrial thickness was routinely measured on the day of hCG triggering or 1 day prior. The prevalence of an endometrial lining <8 mm was compared between PGT-M patients and controls. Hormonal contraceptive use (both duration and cessation interval) was compared between both groups. Univariable and multivariable regression analyses were performed to identify risk factors for thin endometrial lining. In addition, cycle and pregnancy outcomes were compared within control/PGT-M groups between patients with endometrial lining > or <8 mm.

MAIN RESULTS AND THE ROLE OF CHANCE

Thin endometrial lining on the day of hCG triggering was found significantly more often in the PGT-M group, compared to controls: 32% vs 11% (mean difference 21.0%, 95% CI: 11.7, 30.3%). As expected, more patients in the PGT-M group ceased their hormonal contraception late (<1 year): 64% vs 2% in the control group (mean difference 61.9%, 95% CI: 53.0, 70.8%). Average duration of hormonal contraceptive use was 10.6 years in the PGT-M group vs 9.3 years in controls (mean difference 1.3 years, 95% CI: 0.2, 2.3 years). Multivariable logistic regression analysis identified late cessation (OR: 6.0, 95% CI: 1.9-19.2) and duration of prior hormonal contraceptive use (OR per year increase 1.1, 95% CI: 1.0-1.2) as significant independent risk factors for a thin endometrial lining. In relation to outcome, we found a statistically significant increase in miscarriage rate in PGT-M patients with an endometrial lining <8 mm compared to those with an endometrial lining >8 mm (20.0% vs 1.7%, mean difference 18.3%, 95% CI: 2.3, 34.3%). A trend towards lower birth weight and gestation- and gender-adjusted birth weight (z-score) was also found in this group. No statistically significant differences were detected in pregnancy rate, live birth rate, or incidence of preterm delivery or SGA. Within the control group, no statistically significant differences were found in outcomes between patients with an endometrial lining <8 compared to an endometrial lining >8 mm.

LIMITATIONS, REASONS FOR CAUTION

The study is retrospective. Various types of hormonal contraceptives were reported which possibly exert different effects on the endometrial lining. In relation to pregnancy outcome measures, numbers were very limited; therefore, no firm conclusions should be drawn.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides further insight into the role of prior hormonal contraceptive use as a possible contributor to the occurrence of thin endometrial lining during ART treatment. Future studies should provide more information on its clinical relevance, to determine whether PGT-M patients can be reassured, or should be counselled to stop hormonal contraceptive use and change to an alternative contraceptive method prior to PGT treatment.

STUDY FUNDING/COMPETING INTERESTS

No specific funding was used and no conflicts of interests are declared.

TRIAL REGISTRATION NUMBER

N/A.

Impact of different endometrial preparation protocols before frozen embryo transfer on pregnancy outcomes: a review

The use of frozen embryo transfer cycles has exponentially increased in the last few years. Optimization of endometrial preparation protocols before frozen embryo transfer is mandatory to further improve pregnancy outcomes. This review will focus on the existing literature with regard to the different available endometrial preparation protocols and their impact on pregnancy outcomes. More specifically, we will focus on programmed, natural, and stimulated frozen embryo transfer cycles. The studies performed on this topic are generally of low quality, and only a few well-performed randomized controlled trials have been published. To date, no strong evidence is available to support the use of 1 preparation method over another in terms of pregnancy outcomes. However, robust data have shown a clearly protective effect of natural frozen embryo transfer cycles against long-term obstetric complications, mainly hypertensive disorders of pregnancy and large for gestational age infants. The introduction of individualized luteal phase support in different endometrial preparation protocols is actually gaining a lot of attention and requires further investigation.

The role of timing in frozen embryo transfer

The process of implantation is characterized by a complex cross-talk between the endometrium and the blastocyst, with the endometrium only being receptive to implantation during a transient window of implantation of approximately 2-3 days during the midsecretory phase. The timing of embryo transfer, including frozen embryo transfer, is therefore critical to the success of implantation. In this article, we discuss various elements that may guide the timing of frozen embryo transfer, including the role of endometrial characteristics such as thickness, days postovulation or length of progesterone administration, stage of the embryo, and the application of endometrial receptivity tests to guide personalized embryo transfer.

Observations on clinical assessment of endometrial receptivity

This brief review will examine the investigation of the endometrial cavity before embryo transfer using various techniques, including hysteroscopy, endometrial biopsy using immunohistochemistry and molecular microarray, and ultrasound imaging. All these investigative tools are presently subject to controversy and require large prospective controlled trials for validation. During embryo transfer, the occurrence of a retained embryo does not appear to have a negative impact on pregnancy outcome, and finally, consistent data indicate that physical activity immediately after embryo transfer has no impact on pregnancy outcome.

P16 and P21 are involved in the pathogenesis of endometrial thinning: A cross-sectional study

P16 plays a role in the negative regulation of cell proliferation, regulating cell apoptosis to control the growth of tumor cells. P21 is a nuclear protein that suppresses DNA synthesis and inhibits cell division. This study aimed to examine the expression and roles of P16 and P21 in endometrial thinning. Thirty cases of endometrial biopsy diagnosed as endometrial thinning were assessed by p16 and p21 immunohistochemistry from March 2014 to August 2020 in Huazhong University of Science and Technology Union Shenzhen Hospital. Another thirty cases of normal endometrium in the same period were assessed as controls. The specimens underwent histological analysis, and P16 and P21 were assessed by immunohistochemistry. There were no statistically significant differences in age, menstrual cycle, BMI, sex hormone levels, gravidity and parity between the two groups (all P > .05). In the endometrial thinning group, P16 was expressed in the endometrial adenoid nucleus, cytolymph and interstitial cell nucleus. In the normal group, P16 was mainly expressed in the endometrial adenoid nucleus, with some P16 signals detected in the endometrial interstitial nucleus. P21 expression was mainly detected in the endometrial adenoid nucleus. P16 and P21 amounts in endometrial thinning cases were significantly lower than those of the normal endometrial group. There was no correlation between p16 and p21 amounts. This study revealed aberrant expression of P16 and P21 in the endometrium might be due to a compensatory effect of the thin endometrium to increase cell proliferation and suppress cell apoptosis. However, the pathological roles of P16 and P21 in endometrial thinning and the contribution of cell senescence deserve further investigation.

Is early-follicular long-acting GnRH agonist protocol an alternative for patients with polycystic ovary syndrome undergoing in vitro fertilization?

BACKGROUND

We aimed to compare the clinical and perinatal outcomes of patients with polycystic ovary syndrome (PCOS) undergoing in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) treatment with either an early-follicular long-acting gonadotropin-releasing hormone agonist (GnRH-a) long protocol (EFLL) or a midluteal short-acting GnRH-a long protocol (MLSL).

METHODS

This single-center, retrospective study, included patients with PCOS who underwent IVF/ICSI from January 2013 to June 2019 at the First Affiliated Hospital of Zhengzhou University, Zhengzhou, China. Patients underwent either MLSL (1179 cycles) or EFLL (2390 cycles). The primary outcomes were pregnancy outcomes, perinatal and maternal complications.

RESULTS

Fresh embryo transfer (59.12% vs. 55.47%, P = 0.038), clinical pregnancy (75.23% vs. 53.82%, P = 0.001), and live birth rates (63.27% vs. 42.05%, P = 0.010) were higher in the EFLL group. However, the proportion of patients "freezing all" for high risk of ovarian hyperstimulation syndrome (OHSS) (24.27% vs. 32.06%, P = 0.001) and ectopic pregnancy (1.51% vs. 5.97%, P = 0.002) were lower in the EFLL group than in the MLSL group. The incidence of gestational diabetes was higher in the EFLL group than in the MLSL group (5.08% vs. 1.42%, RR 3.714, 95% confidence interval (CI) 1.474-9.360, P = 0.003). There were no significant differences in the incidence of hypertension, premature rupture of membranes, placenta previa, congenital heart disease, or neonatal weight between the two groups. Logistic regression results showed that age (OR 0.966, 95% CI 0.941-0.993, P = 0.013), treatments (OR 2.380, 95% CI 1.833-3.089, P = 0.001), and endometrial thickness on trigger day (OR 1.115, 95% CI 1.070-1.162, P = 0.001) were correlated with clinical pregnancy. Pre-pregnancy BMI (OR 1.098, 95% CI 1.002-1.204, P = 0.046), fasting plasma glucose (FPG) (OR 3.096, 95% CI 1.900-5.046, P = 0.001), and treatments (OR 3.458, 95% CI 1.359-8.800, P = 0.009) were correlated with gestational diabetes mellitus (GDM). Treatments (OR 0.291, 95% CI 0.148-0.575, P = 0.001) and endometrial thickness on trigger day (OR 0.834, 95% CI 0.722-0.962, P = 0.013) were correlated with ectopic pregnancy.

CONCLUSION

The early-follicular long-acting GnRH agonist long protocol can be used as an ideal assisted reproductive technology (ART) pregnancy assistance program for patients with PCOS, but obese patients should be encouraged to lose weight before ART treatments to reduce the risk of GDM.