Impaired implantation in endometriosis compared with couples with male subfertility after transfer of equal quality embryos: a matched cohort study

Endometriosis and IVF treatment outcomes: unpacking the process

Advanced endometriosis is associated with a reduction of IVF success. Surgical damage to the ovarian reserve following the excision of endometriomas has been claimed as a critical factor in the explanation of this detrimental effect. However, it is generally inferred that other mechanisms might also hamper IVF success in affected women. They include diminished responsiveness to ovarian stimulation, altered steroidogenesis, a decline in oocyte quality, reduced fertilization and embryo development, and impaired implantation. To navigate these limitations, we scrutinized available literature for studies specifically designed to address distinct phases of the IVF process. Utmost consideration was given to intra-patient ovarian response comparisons in women with unilateral endometriomas and to studies applying a meticulous matching to control confounders. The following observations have been drawn: 1) endometriosis has a negligible impact on ovarian response. A slight reduction in stimulation response can only be observed for endometriomas larger than 4 cm. Follicular steroidogenesis is unaffected; 2) oocyte quality is not hampered. Fertilization rates are similar, and intracytoplasmic sperm injection (ICSI) is not justified. Embryonic development is uncompromised, with no increase in aneuploidy rate; 3) endometrial receptivity is either unaffected or only slightly impacted. In conclusion, our study suggests that, aside from the well-known negative effect on ovarian reserve from excisional endometrioma surgeries, endometriosis does not significantly affect IVF outcomes.

Higher miscarriage rate in subfertile women with endometriosis receiving unbiopsied frozen-warmed single blastocyst transfers

Background: Assisted reproductive technology treatment is recommended to overcome endometriosis-associated infertility but current evidence is controversial. Endometriosis is associated with lower antral follicle count (AFC) and oocyte yield but similar clinical outcomes compared to controls. Unaffected ovarian stimulation response and embryological outcomes but lower clinical pregnancy and live birth rates and higher miscarriage rates have been reported, implying direct impact on endometrial receptivity. With evidence emerging on the benefit of frozen-warmed and blastocyst stage transfer, we investigated ART outcomes in endometriosis using homogeneous case-control groups. Methods: This is a retrospective observational case-control study including n = 66 frozen-warmed unbiopsied single blastocyst transfers of patients with endometriosis and n = 96 of women exhibiting idiopathic sterility. All frozen-warmed transfers followed artificial endometrial preparation. Results: In control women, the mean number of oocytes recovered at oocyte pick up was higher compared to women with endometriosis (15.3 ± 7.1 vs. 12.7 ± 5.2, p = 0.025) but oocyte maturation index (mature oocytes/total oocytes at oocyte pick up) was significantly higher for endometriosis (48.2% vs. 34.0%, p = 0.005). The same was shown for the subgroup of 44 endometriosis patients after endometrioma surgery when compared with controls (49.1% vs. 34.0%, p = 0.014). Clinical pregnancy rate was not higher in endometriosis but was close to significance (47.0% vs. 32.3%, p = 0.059) while live birth rate was comparable (27.3% vs. 32.3%, p = 0.746). Miscarriage rate was higher in the endometriosis group (19.7% vs. 7.3%, p = 0.018). A significantly higher AFC was observed in the control group in comparison with the endometriosis group (16.3 ± 7.6 vs. 13.4 ± 7.0, p = 0.014). Live birth rate did not differ when comparing all endometriosis cases (p = 0.746), ASRM Stage I/II and Stage III/IV (p = 0.348 and p = 0.888) with the control group but the overall pregnancy rate was higher in ASRM Stage I/II (p = 0.034) and miscarriage rate was higher in ASRM Stage III/IV (p = 0.030) versus control. Conclusion: Blastocyst transfers in women with endometriosis originate from cycles with lower AFC but higher share of mature oocytes than in control women, suggesting that endometriosis might impair ovarian reserve but not stimulation response. A higher miscarriage rate, independent of blastocyst quality may be attributed to an impact of endometriosis on the endometrium beyond the timing of implantation.

Implantation Failure in Endometriosis Patients: Etiopathogenesis

Embryo implantation requires adequate dialogue between a good quality embryo and a receptive endometrium. This implantation is still considered as the black box of reproductive medicine. Endometriosis is a highly prevalent chronic inflammatory disease, concerning about 10% of women of reproductive age and is one of the major causes of female infertility. The mechanisms involved in endometriosis-related infertility, an event not yet completely understood, are multifactorial and include anatomical changes, reduction in ovarian reserve, endocrine abnormalities, genetic profile, immunity markers, inflammatory mediators, or altered endometrial receptivity. In this article, we will focus on the impact of endometriosis on embryo quality and on endometrial receptivity. Results: Poor oocyte and embryo quality seem to promote a lower pregnancy rate, more than the endometrium itself in women with endometriosis. Other studies report the contrary. In addition, hormonal imbalance observed in the endometrium could also alter the embryo implantation. Conclusions: Controversial results in the literature add difficulties to the understanding of the mechanisms that lead to embryo implantation disorders. Furthermore, either oocyte/embryo impairment, altered endometrium, or both may cause impaired implantation. New prospective, randomized, and controlled studies are necessary to determine the origin of the defects that make conception more difficult in the case of endometriosis and adenomyosis.

The mid-secretory endometrial transcriptomic landscape in endometriosis: a meta-analysis

STUDY QUESTION

Do women with endometriosis have a different endometrial gene expression profile at the time of embryo implantation than women without endometriosis?

SUMMARY ANSWER

The endometrial gene expression profile of women with endometriosis differs from that of women without endometriosis at the mid-secretory phase, although the differences are small.

WHAT IS KNOWN ALREADY

About 50% of women with endometriosis suffer infertility. Several molecular studies have suggested impaired endometrial receptivity in women with endometriosis, while others have detected no dysregulation of endometrial receptivity. Nevertheless, the previous endometrial transcriptome studies comparing women with and without endometriosis have been performed in small sample size with limited statistical power. We set out to systematically search and compile data of endometrial gene expression signatures at the receptive phase in women with endometriosis versus control women. Based on the obtained data, we conducted a meta-analysis of differentially expressed genes in order to raise the power of the analysis for identifying the molecular profiles of receptive phase endometria in endometriosis.

STUDY DESIGN, SIZE, DURATION

A systematic literature search was conducted up to February 2022 following PRISMA criteria and included PubMed, Cochrane and Web of Science databases. For the systematic search, the term ‘endometriosis’ was paired with the terms ‘transcriptomics’, ‘transcriptome’, ‘gene expression’, ‘RNA-seq’, ‘sequencing’ and ‘array’, by using the Boolean operator ‘AND’ to connect them. Articles written in English were screened and interrogated for data extraction.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A meta-analysis was performed on the selected studies to extract the differentially expressed genes described at the mid-secretory phase in women with endometriosis versus women without endometriosis in natural cycles, using the robust rank aggregation method. In total, transcriptome data of 125 women (78 patients and 47 controls) were meta-analysed, with a special focus on endometrial receptivity-specific genes based on commercial endometrial receptivity tests.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 8 studies were eligible for the quantitative meta-analysis, gathering transcriptome data from the mid-secretory phase endometria of 125 women. A total of 7779 differentially expressed transcripts between the study groups were retrieved (3496 up-regulated and 4283 down-regulated) and were meta-analysed. After stringent multiple correction, there was no differential expression of any single molecule in the endometrium of women with endometriosis versus controls, while enrichment analysis detected that the pathways of chemotaxis and locomotion are dysregulated in endometriosis. Further analysis of endometrial receptivity-specific genes highlighted dysregulation of C4BPA, MAOA and PAEP and enrichment of immune and defence pathways in women with endometriosis.

LIMITATIONS, REASONS FOR CAUTION

Most of the studies included into the meta-analysis were relatively small and had different study designs, which might have contributed to a bias.

WIDER IMPLICATIONS OF THE FINDINGS

The current meta-analysis supports the hypothesis that endometrial receptivity is altered in women with endometriosis, although the changes are small. The molecules and pathways identified could serve as future biomarkers and therapeutical targets in detecting and treating endometriosis-associated infertility.

STUDY FUNDING/COMPETING INTEREST(S)

The authors declare no competing interests. This work was supported by the Spanish Ministry of Education, Culture and Sport [grant FPU15/01193] and the Margarita Salas program for the Requalification of the Spanish University system [grant UJAR01MS]; Spanish Ministry of Economy, Industry and Competitiveness (MINECO) and European Regional Development Fund (FEDER): grants RYC-2016-21199 and ENDORE SAF2017-87526-R; Programa Operativo FEDER Andalucía (B-CTS-500-UGR18; A-CTS-614-UGR20); the Junta de Andalucía [BIO-302; and PAIDI P20_00158]; the University of Jaén [PAIUJA-EI_CTS02_2017]; the University of Granada, Plan Propio de Investigación 2016, Excellence actions: Units of Excellence; Unit of Excellence on Exercise and Health (UCEES), and by the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades and European Regional Development Fund (ERDF), ref. SOMM17/6107/UGR; the Estonian Research Council (grant PRG1076); Horizon 2020 innovation (ERIN, grant no. EU952516) of the European Commission and Enterprise Estonia (grant EU48695).

TRIAL REGISTRATION NUMBER

The systematic review was registered at PROSPERO (identifier: CRD42020122054).

Impact of endometriosis on oocyte morphology in IVF-ICSI: retrospective study of a cohort of more than 6000 mature oocytes

BACKGROUND

Infertility associated with endometriosis can be explained by several non-exclusive mechanisms. The oocyte plays a crucial role in determining embryonic competence and this is particularly relevant for in vitro fertilization (IVF) outcomes. According to some authors, the morphology of oocytes could also be a non-invasive marker of oocyte quality. The aim of this study was to evaluate the relationship between endometriosis and oocyte morphology after controlled ovarian stimulation for intracytoplasmic sperm injection (ICSI) on a large oocyte cohort.

METHODS

Single-center comparative retrospective study in the academic In Vitro Fertilization (IVF) unit of the Lille University Hospital. A total of 596 women treated for IVF-ICSI with ejaculated spermatozoa for sperm alterations were included. They were classified as endometriosis (n = 175) or control groups (n = 401). The morphological evaluation of 2,016 mature oocytes from 348 cycles of patients with endometriosis was compared with that of 4,073 mature oocytes from 576 control cycles. The main outcome measures were Average Oocyte Quality Index (AOQI) and metaphase II oocyte morphological scoring system (MOMS). Comparison of groups was carried out by a mixed linear model and by a generalized estimation equation model with a "patient" random effect to consider that a patient might have several attempts.

RESULTS

No difference in AOQI and MOMS scores was found between endometriosis and control women (adjusted p = 0.084 and 0.053, respectively). In case of endometriosis, there were significantly fewer metaphase II oocytes retrieved, embryos obtained, grade 1 embryos and number of cumulative clinical pregnancies compared to controls. In the endometriosis group, endometriosis surgery was associated with a reduced number of mature oocytes retrieved, and the presence of endometrioma(s) was associated with some abnormal oocyte shapes. Nevertheless, no difference concerning the AOQI and MOMS scores was found in these subgroups.

CONCLUSION

Endometriosis does not have a negative impact on oocytes' morphology in IVF-ICSI.

TRIAL REGISTRATION

On December 16, 2019, the Institutional Review Board of the Lille University Hospital gave unrestricted approval for the anonymous use of all patients' clinical, hormonal and ultrasound records (reference DEC20150715-0002).