Implantation failures in women with infertility associated endometriosis

Effects of various controlled ovarian hyperstimulation protocols and surgery on pregnancy outcomes in women with endometriosis

Endometriosis is a common gynecological condition in women of childbearing age that causes symptoms such as menstrual changes and dysmenorrhea, and is also a major cause of infertility. Therefore, women with endometriosis usually need to use assisted reproductive technology (ART), such as in vitro fertilization or intracytoplasmic sperm injection, to increase their chances of conceiving. Numerous clinical observations and studies have indicated that endometriosis can affect the success of ART, such that women with endometriosis who use ART have a lower live-birth rate than those without endometriosis who use ART. Therefore, this article reviews the impact of various controlled ovarian hyperstimulation protocols and surgery on the pregnancy outcomes of women with endometriosis using ART to explore the selection of individualized treatment.

Histopathologic characteristics of term placentas in singleton pregnancies in women with endometriosis-related infertility after ART treatment: case-control study

OBJECTIVES

Endometriosis is one of the leading causes of infertility, due to negative impact on ovarian folliculogenesis and endometrial receptivity. Literature show that endometriosis could be associated with perinatal complications such as preterm birth (PTB) and preeclampsia (PE). Authors hypothesized that women with endometriosis-related infertility conceived by assisted reproductive technology (ART) treatment have higher frequency of placental disorders. Main outcome is the occurrence of histopathologic alterations of term placentas in singleton pregnancies of women with endometriosis conceived by ART treatment, compared to healthy women with infertility due to male factor (MF) conceived by ART and to healthy women with spontaneous pregnancies. Secondary outcome include the occurrence of perinatal complications and the relationship of endometriosis and placental histopathologic characteristics.

METHODS

Single-center, case-control study of term placentas that were collected within Department of Obstetrics and Gynecology of University Hospital Center (UHC) Split and analyzed in the Pathology department of the same hospital, by one senior perinatal pathologist. Histopathologic analysis was reported using Amsterdam Placental Workshop Group Consensus. All the noted placental lesions were divided into following categories: anatomic, inflammatory, villous maturation and vascular malperfusion disorders. Required sample size was 80 placentas, and study results were reported with descriptives, and analyzed with chi-squared, Fisher's exact test and Kruskal-Wallis ANOVA. Multivariate regression analysis was carried with adjustment for confounding factors. Ethics approval: Class n. 520-03/24-01/83.

RESULTS

Study included term placentas of 107 women, of which 36 were women with endometriosis conceived by ART, 31 were healthy women with MF infertility conceived by ART and 40 healthy women with spontaneous pregnancies. Endometriosis women were predominantly primiparas, with longer infertility duration. Endometriosis group had higher occurrence of early pregnancy bleeding and imminent preterm labor. Endometriosis and MF groups had higher occurrence of Cesarian delivery (CS), while endometriosis group had newborns with lowest birthweight. Endometriosis group had shorter placental cords (PC), higher rates of increased syncytial knotting and vascular malperfusion disorders (subchorionic and perivillous fibrin, intervillous thrombosis, high grade fetal vascular malperfusion). Finally, endometriosis is showed to be associated with increased syncytial knots' formation and PC hypercoiling, after adjustment for confounding factors in the multivariate regression analysis.

CONCLUSIONS

Despite low rates of perinatal complications, we report endometriosis to have higher occurrence of increased syncytial knotting and vascular malperfusion placental disorders, compared to control groups. Endometriosis is also associated with increased syncytial knotting and PC hypercoiling. Further studies are needed to elucidate the endometriosis impact on endometrial receptivity and immunopathogenesis in placental disorders and perinatal complications.HighlightsEndometriosis women were predominantly primiparas, with longer infertility duration.Endometriosis group had higher occurrence of early pregnancy bleeding and imminent preterm labor. Moreover, endometriosis and MF groups had higher occurrence of Cesarian delivery, while endometriosis group had newborns with lowest birthweight.Endometriosis group had shorter placental cords, higher rates of increased syncytial knotting and vascular malperfusion lesions.Endometriosis is showed to be associated with increased syncytial knots formation and hypercoiling of placental cord, after adjustment for confounding factor.

Indirect markers of oocyte quality in patients with ovarian endometriosis undergoing IVF/ICSI: a systematic review and meta-analysis

This systematic review and meta-analysis aimed to evaluate the impact of ovarian endometriomas (OMA) on indirect markers of oocyte quality in patients undergoing IVF, compared with women without anatomical or functional ovarian abnormalities. The search spanned original randomized controlled trials, case-control studies and cohort studies published in MEDLINE, the Cochrane Controlled Trials Register and the ClinicalTrials.gov database up to October 2023. Thirty-one studies were included in the meta-analysis, showing no significant differences in fertilization (OR 1.10, 95% CI 0.94-1.30), blastulation (OR 0.86, 95% CI 0.64-1.14) and cancellation (OR 1.06, 95% CI 0.78-1.44) rates. However, patients with OMA exhibited significantly lower numbers of total and mature (metaphase II) oocytes retrieved (mean difference -1.59, 95% CI -2.25 to -0.94; mean difference -1.86, 95% CI -2.46 to -1.26, respectively), and lower numbers of top-quality embryos (mean difference -0.49, 95% CI -0.92 to -0.06). The Ovarian Sensitivity Index was similar between the groups (mean difference -1.55, 95% CI -3.27 to 0.18). The lack of data published to date prevented meta-analysis on euploidy rate. In conclusion, although the presence of OMA could decrease the oocyte yield in patients undergoing IVF/intracytoplasmic sperm injection, it does not appear to have an adverse impact on oocyte quality.

The involvement of RNA N6-methyladenosine and histone methylation modification in decidualization and endometriosis-associated infertility

Defective decidualization of endometrial stromal cells (ESCs) in endometriosis (EM) patients leads to inadequate endometrial receptivity and EM-associated infertility. Hypoxia is an inevitable pathological process of EM and participates in deficient decidualization of the eutopic secretory endometrium. Enhancer of zeste homology 2 (EZH2) is a methyltransferase which catalyses H3K27Me3, leading to decreased expression levels of target genes. Although EZH2 expression is low under normal decidualization, it is abundantly increased in the eutopic secretory endometrium of EM and is induced by hypoxia. Chromatin immunoprecipitation-PCR results revealed that decidua marker IGFBP1 is a direct target of EZH2, partially explaining the increased levels of histone methylation modification in defected decidualization of EM. To mechanism controlling this, we examined the effects of hypoxia on EZH2 and decidualization. EZH2 mRNA showed decreased m6 A modification and increased expression levels under hypoxia and decidualization combined treatment. Increased EZH2 expression was due to the increased expression of m6 A demethylase ALKBH5 and decreased expression of the m6 A reader protein YTHDF2. YTHDF2 directly bind to the m6 A modification site of EZH2 to promote EZH2 mRNA degradation in ESCs. Moreover, selective Ezh2 depletion in mouse ESCs increased endometrial receptivity and improved mouse fertility by up-regulating decidua marker IGFBP1 expression. This is the first report showing that YTHDF2 can act as a m6 A reader to promote decidualization by decreasing the stability of EZH2 mRNA and further increasing the expression of IGFBP1 in ESCs. Taken together, our findings highlight the critical role of EZH2/H3K27Me3 in decidualization and reveal a novel epigenetic mechanism by which hypoxia can suppress EM decidualization by decreasing the m6 A modification of EZH2 mRNA.

Evaluation of endometrioma size effect on ovarian reserve, embryo quality and pregnancy outcome after in vitro fertilization cycle; a cross-sectional study

INTRODUCTION

Investigation of endometrioma size and its laterality on the quality of the embryo in patients with endometrioma compared to healthy subjects.

MATERIALS AND METHODS

In this retrospective and cross-sectional study, 70 patients with unilateral and bilateral endometrioma were recruited and compared with 70 age-matched infertile patients as the control group in terms of AMH before ovum pick-up, embryo quality as well as pregnancy outcome. Additionally, in the case group, we divided both unilateral (n = 32) and bilateral endometrioma patients (n = 38) into three groups based on the size of endometrioma. (1-3 cm, 3-6 cm, 6-10 cm) RESULTS: There was no difference in terms of age, BMI, parity, and age of menarche between the case and control groups. Moreover, no significant difference was observed in the baseline level of AMH between the case 2.96 ± 2.72 ng/dl (0.21-11.3) and control 2.73 ± 2.39 (0.21-12.8) groups. (P = 0.59) There was also no significant difference concerning AMH level between unilateral 3.58 ± 3.20 ng/dl (0.21-12.8) and bilateral endometrioma 2.45 ± 2.14 (0.21 - 0.20) groups. In terms of the quality and number of embryos, there was no significant difference between the case and control groups. (P = 0.30) Although the AMH level decreased with the increase in endometrioma size, this difference was not statistically significant. (P = 0.07) There was no significant difference in terms of the embryo quality between the groups based on the size of endometrioma. (P = 0.77) In addition, no significant difference was observed between the case and control groups in the terms of birth weight and pregnancy complications, such as premature delivery, cesarean section rate, neonatal respiratory distress, jaundice, as well as hospitalization rate. Head circumference of the newborns was higher in the endometrioma group while their Apgar score was lower in the case compared to the control group.

CONCLUSION

The presence of endometrioma by itself does not affect the main result of IVF procedures, including the number and quality of embryos and pregnancy outcome. Thus, IVF and embryo preservation and even pregnancy before surgery seem to be reasonable for endometriotic patients.

Impact of endometriosis on embryo quality and endometrial receptivity in women undergoing assisted reproductive technology

ART is an important treatment method for infertile patients with endometriosis. However, the effects of endometriosis on embryo quality and endometrial receptivity remain unclear. Thus, we aimed to simultaneously investigate the impact of endometriosis and its stage on embryo quality and endometrial receptivity in women undergoing ART. We retrospectively analyzed the data from patients with and without endometriosis who underwent oocyte retrieval and/or high-quality embryos transfer between July 2015 and December 2020, including 1312 IVF cycles and 608 IVF or frozen-thawed embryo transfer (FET) cycles, respectively. The endometriosis group had a lower percentage of good cleavage-stage embryos and fertilization rates than those in the control group (p = 0.038 and 0.008, respectively). The number of retrieved oocytes, MII oocytes, cleavage, blastocysts, and blastulation rates was comparable between two groups. We found no significant difference in clinical pregnancy, implantation, live birth, miscarriage, or multiple pregnancy rates between the two groups among patients who transferred high-quality embryos. Stratification analysis showed that patients with stage III-IV endometriosis had fewer retrieved oocytes than those with stage I-II endometriosis (p = 0.012) and marginally fewer retrieved oocytes than the control group (p = 0.051). The stage I-II group had the lowest percentage of good cleavage-stage embryos, which was significantly lower than that of the control group (p = 0.043). In FET cycles, patients with stage III-IV endometriosis had a higher miscarriage rate than those in the control group (p = 0.023). Our results suggest that endometriosis does not alter endometrial receptivity but affects embryo quality, oocyte fertilization ability, and ovarian response.

Water-Extracted Prunella vulgaris Alleviates Endometriosis by Reducing Aerobic Glycolysis

Endometriosis is a chronic inflammatory disorder caused by abnormal adhesion of endometrial tissue to the outside of the uterus. The combination of surgery, non-steroidal anti-inflammatory drugs, and hormone treatment is well established therapy for endometriosis, however, case reports have showed that high rates of relapse and unpleasant side effect. For these reasons, recently, the studies have been focused on the Warburg-like metabolic shift of endometriosis. Prunella vulgaris is one of traditionally used herbal medicine for inflammatory disease and the anti-estrogenic effects of P. vulgaris is well-established. Therefore, in this work, we evaluated water-extracted P. vulgaris (PV) as a potential treatment for endometriosis. To this, we artificially induced endometriosis in ovarectomized mice by intra-peritoneal inoculation of uterus extracts. PV was orally administered, and PV significantly alleviated endometriosis, particularly the growth of ectopic endometrial lesions in artificially endometriosis-induced mice. For the mechanism study of anti-endometriosis by PV, we designed an in vitro study using human normal endometrial stromal cells (T-HESCs) and human endometrial cell (12Z) obtained from patients with endometriosis. PV strongly induced the apoptosis of 12Z cells rather than T-HESCs by control the activity or expression of aerobic glycolysis enzymes, such as lactate dehydrogenase A (LDHA), pyruvate dehydrogenase A, and pyruvate dehydrogenase kinase 1/3. In addition, lactate production was enhanced, and oxygen consumption rate was suppressed in 12Z cells upon PV treatment. These changes in aerobic glycolysis eventually caused mitochondrial damage following decreased mitochondrial membrane potential and excessive mitochondrial ROS production. Especially, ulsolic acid (UA), one of the compounds in PV considerably led 12Z cell apoptosis with inhibition of LDHA activity. Therefore, UA could be a major active substance of PV in terms of endometriosis inhibitors. In conclusion, this study provides the evidence that the beneficial efficacy of PV for the prevention/treatment of endometriosis.

Folate metabolism abnormalities in infertile patients with endometriosis

Background: Homocysteine levels can be impacted by enzymes variations. Aim: To correlate MTHFR, MTR and MTRR variants with homocysteine levels in the blood and follicular fluid and assisted reproduction results. Material & methods: MTHFR (rs2274976, rs1801131, rs1801133), MTR (rs1805087) and MTRR (rs1801394) genotyping was performed by TaqMan assays and compared with homocysteine levels, measured by ELISA, to oocytes retrieved and to the pregnancy status of women with endometriosis and controls. Results: The MTR G allele and GG genotype were more common in patients with endometriosis. They also showed lower levels of homocysteine and more clinical gestations. Epistasis analysis showed a model associated with gestational results, composed of MTHFR+MTR variants (CC+AG). Conclusion: The summation effect of variants in genes participating in folate metabolism was associated with pregnancy status in Brazilian women. MTR variants were more observed in endometriosis patients, as well as lower follicular Hcy levels and increased clinical pregnancy results.

Autophagy as a Therapeutic Target of Natural Products Enhancing Embryo Implantation

Infertility is an emerging health issue worldwide, and female infertility is intimately associated with embryo implantation failure. Embryo implantation is an essential process during the initiation of prenatal development. Recent studies have strongly suggested that autophagy in the endometrium is the most important factor for successful embryo implantation. In addition, several studies have reported the effects of various natural products on infertility improvement via the regulation of embryo implantation, embryo quality, and endometrial receptivity. However, it is unclear whether natural products can improve embryo implantation ability by regulating endometrial autophagy. Therefore, we performed a literature review of studies on endometrial autophagy, embryo implantation, natural products, and female infertility. Based on the information from these studies, this review suggests a new treatment strategy for female infertility by proposing natural products that have been proven to be safe and effective as endometrial autophagy regulators; additionally, we provide a comprehensive understanding of the relationship between the regulation of endometrial autophagy by natural products and female infertility, with an emphasis on embryo implantation.

Assisted reproductive treatment outcomes of women with endometriomas: Either with or without previous ovarian surgery

OBJECTIVE

The present study aimed to evaluate and compare the assisted reproductive technique (ART) outcomes of women with endometriomas either with or without prior endometrioma surgery.

MATERIALS AND METHODS

A total of 122 women with endometriomas underwent intracytoplasmic sperm injection-embryo transfer (ICSI-ET) at a tertiary IVF Center, between 2014 and 2019, were included in this retrospective study. Of this group, 38 patients had recurrent endometriomas and 84 patients had primary endometrioma without a previous endometrioma surgery. The outcomes of ART treatment including cancellation rates before ET, numbers of oocytes obtained, implantation, clinical pregnancy and live birth rates were compared between the groups. A logistic regression model including potential confounders as age and presence of male factor infertility was used to evaluate the possible effect of recurrent endometriomas on the live birth.

RESULTS

The baseline characteristics of the groups were similar. The poor ovarian response rate, defined as the harvest of fewer than four oocytes, was identified in 35.7% and 42.1% of primary and recurrent endometrioma groups, respectively. The implantation (27.2 ± 42.7% vs 24.1 ± 41.4%, P = .74), clinical pregnancy/ET (30.9% vs 27.6%, P = .93 ) and live birth rates/ET (22.1% vs 17.2%, P = .79) CONCLUSION: The ART outcomes of patients with primary and recurrent endometriomas do not seem different in terms of response to ovarian stimulation and live birth rates after ICSI. These results may indicate that the recurrence of the endometrioma might not have a further detrimental effect on ART outcome than the disease itself.

Early embryo development anomalies identified by time-lapse system: prevalence and impacting factors

RESEARCH QUESTION

What is the prevalence of embryo abnormal early cleavage (ACL) identified by time lapse and factors related to patients and treatment that explain ACL occurrence?

DESIGN

A single-centre, retrospective cohort study. Data were collected on all IVF cycles for which embryos were observed in the EmbryoScope® between December 2015 and August 2017. Only diploid zygotes cleaved on day 2 were included. The study included 318 cycles (250 couples and 1343 embryos). Embryo videos were retrospectively analysed for ACL. The prevalence of each type of ACL was recorded. The influence of clinical factors (whether they were intrinsic to patients or specific to IVF treatment) on ACL occurrence was analysed in multivariate multilevel mixed-effect logistic regression analysis.

RESULTS

A high prevalence of ACL was observed: 37.6% (505/1343) of embryos presented at least one ACL, 22.8% (306/1343) a trichotomous mitosis, 25.8% (347/1343) a rapid cleavage, 6.7% (90/1343) a cell fusion and two or more ACL (16.1%). Part of the variation (12-25%) in ACL occurrence could be explained by embryo origin. Trichotomous mitosis and two or more ACL phenotypes were less likely to occur in women with endometriosis or tubal pathology and tubal pathology alone, respectively. No factor related to IVF cycles was found to be statistically associated with ACL occurrence.

CONCLUSIONS

Our findings emphasize the importance of considering embryo origin when interpreting studies focusing on embryo characteristics and factors that could affect their quality. The present study is limited by a small sample size of known embryo implantations and monocentric criterion.

Serum anti-Mullerian hormone, prolactin and estradiol concentrations in infertile women with endometriosis

OBJECTIVE

Endometriosis is a benign gynecological disease, which significantly impairs fertility. However, the contribution of specific hormonal parameters to the proper diagnosis of endometriosis in infertility states has not been adequately determined. The aim of this study was to compare ant-Mullerian hormone (AMH), prolactin and estradiol concentrations between infertile women with and without endometriosis, as well as to estimate the effect of endometrioid heterotopia on ovarian reserve.

METHODS

In this cross-sectional study, mean baseline serum AMH, prolactin and estradiol levels were assessed in infertile women with and without endometriosis. Descriptive statistics are presented in the form of arithmetic mean ± standard deviation (SD). The comparison of indicators was performed by using parametric (t-test) and non-parametric criteria (Mann-Whitney).

RESULTS

Seventy-two infertile women with endometriosis (group A; mean age: 32 ± 4.3 years) and 77 infertile women without endometriosis (group B; mean age: 32.4 ± 3.7 years) were studied. Mean baseline prolactin concentrations were higher in group A (16.9 ± 5.7 ng/mL) compared with group B (15 ± 4.3 ng/mL; p = .023), whereas mean AMH concentrations were lower (2.8 ± 1.9 ng/mL and 3.5 ± 1.8 ng/mL, respectively; p = .018). The highest prolactin and the lowest AMH concentrations were found in women with ovarian endometriomas than in those with deep infiltrative endometriosis and adenomyosis. There was no difference in estradiol levels between groups.

CONCLUSIONS

Infertile women with endometriosis demonstrated higher prolactin and lower AMH concentrations, compared with infertile women without endometriosis. The highest prolactin and the lowest AMH concentrations were observed in patients with ovarian endometriomas.

Follicular Fluid from Infertile Women with Mild Endometriosis Impairs In Vitro Bovine Embryo Development: Potential Role of Oxidative Stress

OBJECTIVE

 To investigate whether follicular fluid (FF) from infertile women with mild endometriosis (ME) alters in vitro bovine embryo development, and whether the antioxidants N-acetyl-cysteine (NAC) and/or L-carnitine (LC) could prevent such damages.

METHODS

 Follicular fluid was obtained from infertile women (11 with ME and 11 control). Bovine oocytes were matured in vitro divided in: No-FF, with 1% of FF from control women (CFF) or ME women (MEFF); with 1.5 mM NAC (CFF + NAC, MEFF + NAC), with 0.6 mg/mL LC (CFF + LC, MEFF + LC), or both antioxidants (CFF + NAC + LC, MEFF + NAC + LC). After in vitro fertilization, in vitro embryo culture was performed for 9 days.

RESULTS

 A total of 883 presumptive zygotes were cultured in vitro. No differences were observed in cleavage rate (p = 0.5376) and blastocyst formation rate (p = 0.4249). However, the MEFF group (12.5%) had lower hatching rate than the No-FF (42.1%, p = 0.029) and CFF (42.9%, p = 0.036) groups. Addition of antioxidants in the group with CFF did not alter hatching rate (p ≥ 0.56), and in groups with MEFF, just NAC increased the hatching rate [(MEFF: 12.5% versus MEFF + NAC: 44.4% (p = 0.02); vs MEFF + LC: 18.8% (p = 0.79); versus MEFF + NAC + LC: 30.8% (p = 0.22)].

CONCLUSION

 Therefore, FF from infertile women with ME added to medium of in vitro maturation of bovine oocytes impairs hatching rate, and NAC prevented these damages, suggesting involvement of oxidative stress in worst of oocyte and embryo quality of women with ME.

Endometrial asynchrony in pathogenesis of implantation impairment in women with infertility associated with endometriosis

There is a statistically significant difference in the frequency of implantation in the group of patients with endometriosis associated with infertility compared with the control group. This has been confirmed by a number of different studies. The aim of the study to expand the understanding of the pathogenesis of implantation failures in patients with infertility associated with endometriosisMaterials and research methods: The present study included 83 women aged 29 to 43 years (the average age was 33 ± 3.2 years) with a diagnosis of endometriosis (ICD10 code N80.9 Endometriosis, unspecified), as well as infertility (ICD10 code N 97.8, Female infertility of other origin) and repeated implantation failures. All patients of the studied cohort underwent an immunohistochemical study of endometrial biopsy samples taken by the pipel-biopsy of the endometrium during the period of the supposed "implantation window".Research results: Significant decrease in the immunological labeling of VEGF-A in samples from the ERIF group by ∼2.7 times in comparison with EF group (p < .05), the indices of expression of the proapoptotic protein CASP3 are increased in the samples of the ERIF group in comparison with the EF group (by ∼2.7 times, p < .05) and significant decrease in the expression of HOXA10 in the stromal and glandular compartments (2.4 times; 57.2 vs. 23.5%, p < .05).Conclusion: On the basis of the obtained results of the study, it should be concluded that the basis of implantation impairment in patients with repeated implantation failures associated with endometriosis lies in angiogenetic and apoptotic disorders and leads to implantation failure in the eutopic endometrium due to desynchronous transformation of the epithelial-mesenchymal compartment and disruption of endometrial trophism.

The impact of endometrioma on in vitro fertilisation/intra-cytoplasmic injection IVF/ICSI reproductive outcomes: a systematic review and meta-analysis

Background

Assisted reproductive technologies (ART) such as in vitro fertilisation (IVF) and intra-cytoplasmic sperm injection (ICSI) are often used to aid fertility in women with endometrioma; however, the implications of endometrioma on ART are unresolved.

Objective

To determine the effect of endometrioma on reproductive outcomes in women undergoing IVF or ICSI.

Methods

A systematic review and meta-analysis was conducted to identify articles examining women who had endometrioma and had undergone IVF or ICSI. Electronic searches were performed in PubMed, BIOSIS and MEDLINE up to September 2019. The primary outcome was live birth rate (LBR). Secondary outcomes included clinical pregnancy rate (CPR), implantation rate (IR), number of oocytes retrieved, number of metaphase II (MII) oocytes retrieved, number of embryos and top-quality embryos and the duration of gonadotrophin stimulation and dose.

Results

Eight studies were included. Where significant heterogeneity between studies was identified, a random-effects model was used. The number of oocytes (weighted means difference; WMD-2.25; 95% CI 3.43 to − 1.06, p = 0.0002) and the number of MII oocytes retrieved (WMD-4.64; 95% CI 5.65 to − 3.63, p < 0.00001) were significantly lower in women with endometrioma versus controls. All other outcomes, including gonadotrophin dose and duration, the total number of embryos, high-quality embryos, CPR, IR and LBR were similar in women with and without endometrioma.

Conclusion

Even though women with endometriomas had a reduced number of oocytes and MII oocytes retrieved when compared to women without, no other differences in reproductive outcomes were identified. This implies that IVF/ICSI is a beneficial ART approach for women with endometrioma.

Identifying Mechanisms of Endometriosis-Associated Reduced Fecundity in a Rat Model: Novel Insights toward Understanding Human Infertility

The existence of endometriosis has been known since at least the nineteenth century, yet the lack of understanding of causes of infertility and therefore inadequate treatment approaches in endometriosis creates a significant challenge in reproductive medicine. Women worldwide suffer not only pain and infertility but also economical, societal, and physiological burdens. Studies of reproductive events in women are difficult to conduct due to a host of confounding personal and environmental factors and ethically limited due to the very nature of working with reproductive tissues and cells, especially embryos. Animal models are a viable adjunct to study mechanisms causing human reproductive anomalies and infertility in endometriosis. This chapter discusses reproductive anomalies causing infertility in endometriosis and well-established animal models which help decipher the problems and lead to heretofore unknown nonsurgical, nonhormonal methods to manage endometriosis in women. In addition, studies of effects of developmental exposure to endometriosis are revealing for the first time, in both female and male offspring, transgenerational subfertility in a rat model providing insights into the familial nature of endometriosis and possible epigenetic involvement.