Investigating Unilateral Ovarian Endometrioma's Effect on Ova and Embryo Quality in 409 Infertile Endometriotic Patients

ABSTRACT

Purpose

In women with unilateral endometriosis, how do ovarian endometriomas and their inflammatory content affect oocyte and embryo quality in affected versus healthy ovaries, and what is the impact on ART outcomes?

Methods

This study, conducted from March 2022 to March 2024 at Shiraz University of Medical Sciences, assessed infertility outcomes in patients with unilateral endometriomas. It analyzed reproductive parameters (total follicles, oocytes, and embryos quantity and quality) from affected and healthy ovaries, while considering endometrioma size and AMH levels.

Results

This study analyzed ovum pickups and ART outcomes in 409 women with unilateral ovarian endometriosis, revealing critical insights into reproductive performance. Participants had an average age of 33.55 years and a basal AMH level of 2.26 ng/dL, categorized into poor (25.2%), normal (57.2%), and high (17.6%) responders based on their AMH levels. Comparison of outcomes showed that healthy ovaries yielded significantly more MII oocytes, total embryos, and Grade C embryos than affected ovaries, although no significant differences were found across various endometrioma sizes regarding follicular development and egg/embryo quality (p > 0.05). Notably, the good responder group outperformed others in terms of GV oocytes, MII oocytes, and total embryos retrieved. Ultimately, among 40 embryo transfers conducted, 21 resulted in successful pregnancies (52.5%).

Conclusion

Endometriomas lead to fewer M2, total fertilization rate. However, embryo quality remains unchanged. Future studies should compare ART outcomes in operated and non‐operated ovaries and assess deep infiltrating endometriosis's impact on egg quality and quantity.

1. Introduction

Endometriosis affects 10% of women of reproductive age and is a leading cause of infertility, with a prevalence of 30%–50%. Various mechanisms may contribute to infertility in endometriosis, including disruptions in pelvic anatomy, reduced quantity and quality of eggs and embryos, endocrine and immunological disorders, increased cytokines and inflammatory markers linked to iron and nitric oxide in the pelvis and ovaries. Additionally, there may be issues with uterine receptivity [1, 2, 3, 4, 5]. In this regard, ART is a suitable option for treating infertility in patients with endometriosis. While there is consensus on the reduced ovarian reserve following endometrioma surgery—especially in bilateral and severe cases involved with DIE—debate continues regarding the timing of endometriosis surgery before assisted reproductive technology (ART) to improve the fertility outcomes [6, 7]. This uncertainty partly arises from doubts about how endometriosis affects egg and embryo quality [8, 9, 10, 11].

Various factors contribute to reduced egg and embryo quality in endometriosis patients. Ovarian endometriomas cause local pelvic inflammation and higher oxidative stress, increased levels of reactive oxygen species and iron‐mediated oxidative stress leading to altered oocyte quality of eggs. Sanchez's study demonstrated that iron levels in the follicular fluid of affected ovaries are higher than in healthy ones in cases of unilateral endometrioma. While some research indicates that the quality of eggs and embryos in endometriosis patients is lower than in healthy individuals (unexplained infertility, tubal factor, and mild to moderate male factor infertility), other studies show that their egg quality can be comparable to that of healthy women [12, 13].

Some studies have examined pregnancy outcomes in women with endometriosis compared to healthy controls using both donated and their own eggs in both fresh and FET cycle transfer, yielding contradictory results. Most of them emphasize that if endometriosis patients have high‐quality embryos, their chances of pregnancy and pregnancy outcomes are similar to those of healthy individuals without endometriosis. However, existing literature on egg quality in these patients often suffers from inadequate sample sizes or focuses solely on granulosa cells and follicular fluid content, neglecting the male partner's role, additionally, many studies include various types of endometriosis without distinguishing between unilateral and bilateral endometrioma cases [8, 12, 13, 14, 15].

Notably, except for Filippi et al. [16] research on 29 infertile endometriotic patients, there is no research that has separately analyzed egg and embryo quality from affected and healthy ovaries to assess the impact of pelvic and ovarian inflammatory mediators on ART outcomes, or they have only examined and focused on pregnancy rate and pregnancy outcomes as an indicator of pregnancy success in these patients. Thus, we conducted this study for the first time to compare the quality of eggs and embryos from endometriosis patients with unilateral endometrioma. We aimed to assess clinical parameters related to ART data, using the affected ovary as the case group and the unaffected ovary as the control, while also reporting pregnancy outcomes.

2. Material and Methods

This cross‐sectional study was conducted, from May 2023 to March 2024, on patients with endometriomas referred to two private and university hospitals affiliated to Shiraz Universityof Medical Sciences (SUMS) (N = 309) and Guilan University of Medical Sciences (GUMS) (N = 100). SUMS Institutional Review Board approved it (IR.SUMS.MED.REC.1402.133). They were infertile with or without pain, and endometriomas were diagnosed by transvaginal ultrasound (TVUS). The study enrolled infertile women presenting with unilateral, Uni‐locular endometrioma detected by TVUS, irrespective of pain status, who provided informed consent. Patients were excluded if they had previously undergone surgical treatment for endometriosis, received estrogen‐suppressing drugs, such as oral contraceptive pills, danazole, or gonadotropin‐releasing hormone (GnRH) agonists 6 months prior to the study, > 40 years old, severe male factor infertility and those who had plan to use surrogate uterus, egg, or embryo donation. Also, patients with: AMH < 0.5 ng/dL, FSH > 10 IU, autoimmune disease, recurrent implantation failure, PCO, and mullerian duct anomaly were excluded.

2.1. ART Protocol

Antagonist protocol was selected for all the patients. Gonadotropin dose was individualized according to the baseline ovarian reserve tests [follicle‐stimulating hormone (FSH), AMH, antral follicle count (AFC)]. Gonadotropins included recombinant follicle‐stimulating hormone (Cinal‐ f; Cinagen, Iran) and human menopausal gonadotropin (hMG; Menotron; Ronak Daroo, Iran) that were started on the second to third cycle days. After 5 or 6 days, TVUS was done to monitor the follicle response and then every 2–3 days until leading follicle (12 mm) emerges. Then GnRH antagonist (Cetrotide, 0.25 mg; ACTAVIS, UK) was injected to prevent premature luteinizing hormone (LH) surge until triggering day. According to the serum estradiol level and the risk for ovarian hyperstimulation syndrome (OHSS), final oocyte maturation was triggered with human chorionic gonadotropin (10 000 IU of urinary hCG or 250 μg dose of rhCG; Gorarex, Ronak Daroo, Iran) or GnRH agonist (0.2 mg dose of triptorelin; Decapeptyl; Ferring GmbH, Germany) when 2–3 preovulatory follicles reached 17–18 mm in size. Then ovum pick up (OPU) was done 36 h later. At this stage, the eggs from the affected and unaffected ovaries were collected and monitored separately during fertilization procedure. For FET cycles, hormone replacement therapy (HRT) with estradiol valerate (2 mg, Aburayhan, Shiraz) started from the cycle day 2–3 till appropriate endometrial thickness reached (ET: 8–9 mm) and tri‐laminar pattern endometrium, then IM progesterone added and continued about 3–5 days prior to ET (depending on the stage of embryo development) which was replaced by vaginal cyclogest (400 mg, ACTAVIS, United Kingdom) throughout the luteal phase.

To assess the effectiveness of oocyte stimulation and retrieval, we calculated the Follicle‐to‐Oocyte Index (FOI) as the ratio of the total number of oocytes retrieved to the baseline antral follicle count (AFC) at the start of ovarian stimulation [17].

2.2. Outcome Measures

Data regarding ART were documented for each ovary, including total number of follicles, number of oocytes and total GV, MI, MII oocytes, and fertilization rate and their quality. The quality of the eggs and embryos retrieved from the affected ovary was carefully evaluated, taking into consideration the size of the endometrioma present (< 3 or > 3 cm) and the AMH levels (< 1, 1–3, and > 3 ng/dL). Embryo grading quality was done according to the Istanbul Consensus Statement, where: Grade G1: Good (A), less than 10% fragmentation, 90% specific cell size for the stage in cells, absence of multinucleation. Grade G2: Fairly good (B), 10%–25% fragmentation, specific cell size for the stage in most cells, absence of multinucleation. Grade G3: Poor (C), severe fragmentation over 25% [18]. The embryos were cultured in standard media and were frozen in cleavage state. This assessment aimed to provide a clearer understanding of how these variables might influence reproductive outcomes. Furthermore, the pregnancy rate following embryo transfer was analyzed; however, it remained uncertain from which specific ovary the embryo that was ultimately transferred had originated. Clinical pregnancy was considered as the detection of gestational sac with fetal heart within endometrial cavity by TVUS at 5 weeks of gestation.

2.3. Statistical Analysis

Statistical analysis was performed using Fisher's exact test, Chi‐squared test, and paired sample t‐test. All the analysis was carried out by the statistical software package for Windows, version 16 (SPSS, Chicago, IL), and p value less than 0.05 was considered statistically significant.

3. Results

In general, a total of 1594 patients with endometriosis visited two treatment centers, among whom 782 had infertility. Based on inclusion and exclusion criteria, 409 individuals ultimately entered the study. This study examined ovum pickups and ART outcomes in 409 women with unilateral uniloculated ovarian endometriosis (Right = 196, Left = 213) and infertility in both normal and affected ovaries.

Participants had an average age of 33.55 ± 3.96 years, husbands' mean age of 36.45 ± 4.59 years, BMI of 25.72 ± 3.34, and average affected ovary cyst size of 4.09 ± 2.18 cm. The basal AMH level was 2.26 ± 2.14 ng/dL. Women were categorized as poor responders (25.2% with AMH < 1 ng/dL), normal responders (57.2% with AMH between 1 and 3 ng/dL), and high responders (17.6% with AMH > 3 ng/dL) based on their AMH level. There was a statistically significant difference in the mean AMH between the group with OMA size < 3 cm (2.21 ± 1.42) and the group with OMA size ≥ 3 (2.31 ± 2.45) cm (p = 0.002).

Table 1 shows a comparison of ovum pickup and ART outcomes between healthy and affected ovaries. In healthy ovaries, there are notably more MII, total embryos, and Grade C embryos compared to the affected ovaries. However, there is no significant difference in other aspects between healthy ovaries and those affected by endometriosis. Ovarian stimulation was effective, as FOI > 50% (61.01 ± 42.92).

TABLE 1.

Comparison of ovum pickup and ART results between healthy and affected ovaries by endometriosis.

Variable	Total (N = 818)	Group		p
		Healthy ovary (N = 409)	Affected ovary (N = 409)
Follicle, Mean ± SD Median (IQR)	7.32 ± 5.51, 6.0 (6.0)	7.46 ± 5.34, 6.50 (6.0)	7.17 ± 5.67, 6.0 (6.0)	0.149*
Total oocyte, Mean ± SD Median (IQR)	3.87 ± 3.06, 3.0 (3.0)	4.01 ± 3.01, 3.0 (4.0)	3.72 ± 3.11, 3.0 (3.0)	0.100*
Follicle‐to‐oocyte index (FOI%), Mean ± SD Median (IQR)	61.01 ± 42.92 56.34 (43.52)	60.26 ± 41.38 57.14 (37.50)	61.77 ± 44.47 54.54 (46.67)	0.783*
GV Oocyte, Mean ± SD Median (IQR)	0.75 ± 1.03, 0.0 (1.0)	0.80 ± 1.01, 1.0 (1.0)	0.69 ± 1.06, 0.0 (1.0)	0.235*
M1, Mean ± SD Median (IQR)	0.89 ± 1.01, 1.0 (1.0)	0.88 ± 1.0, 1.0 (1.0)	0.90 ± 1.02, 1.0 (1.0)	0.899*
M2, Mean ± SD Median (IQR)	3.28 ± 2.51, 3.0 (4.0)	3.44 ± 2.52, 3.0 (4.0)	3.21 ± 2.50, 2.0 (3.0)	0.035*
Embryo, Mean ± SD Median (IQR)	2.14 ± 2.16, 2.0 (2.0)	2.51 ± 2.45, 2.0 (2.0)	1.77 ± 1.76, 1.0 (3.0)	0.016*
Grade A, Mean ± SD Median (IQR)	1.54 ± 1.44, 1.0 (1.0)	1.61 ± 1.53, 1.0 (1.0)	1.47 ± 1.34, 1.0 (2.0)	0.518*
Grade B, Mean ± SD Median (IQR)	0.63 ± 0.87, 0.0 (1.0)	0.66 ± 0.88, 0.0 (1.0)	0.59 ± 0.86, 0.0 (1.0)	0.463*
Grade C, Mean ± SD Median (IQR)	0.81 ± 1.35, 0.0 (1.0)	0.97 ± 1.47, 0.0 (1.0)	0.62 ± 1.17, 0.0 (1.0)	0.013*

Abbreviations: GV, germinal vesicle oocytes; M1, metaphase I oocytes; M2, metaphase II oocytes; Mean ± SD, Mean ± standard deviation.

^*Mann–Whitney test.

Figure 1 presents a comparative analysis of follicular growth, egg, and embryo quality in relation to the size of ovarian endometriomas. In comparison to a healthy ovary, ovaries containing an OMA (Ovarian Matured Adnexal mass) larger than 3 cm and smaller than 3 cm showed differences not only in the total fertilization rate but also in the number of Grade C embryos (p = 0.03, p = 0.034, respectively). Specifically, the mean total fertilization rate and the number of Grade C embryos in the healthy ovary group were significantly higher than in the group with OMA < 3 cm. However, there was no significant difference when comparing with the group with OMA > 3 cm.

FIGURE 1.

Comparative analysis of follicular growth, egg, and embryo quality in relation to the size of ovarian endometriomas (> 3 cm/≤ 3 cm). GV, germinal vesicle oocytes; M1, metaphase I oocytes; M2, metaphase II oocytes. *Significant at level 0.05.

Other variables were not significantly associated with the size of endometrioma (p > 0.05).

Figure 2 compares the mentioned items in the affected ovary based on AMH level in three categories; high, normal, and poor responder. The good responder group had significantly higher numbers of GV (p = 0.0006), MII (p = 0.009), Grade C of embryo (p = 0.006), total embryo (p = 0.0002), and total follicles retrieved (p = 0.024) compared to the other two groups.

FIGURE 2.

Comparative analysis of follicular growth, egg, and embryo quality in relation to the AMH level (< 1, 1–3, and > 3 ng/dL). AMH, anti‐Müllerian hormone; GV, germinal vesicle oocytes; M1, metaphase I oocytes; M2, metaphase II oocytes.

All embryos were accommodated together in a cage. A total of 40 embryo (FET cycle) transfers were carried out, if surgery was not indicated, leading to the successful initiation of 21 (52.5%) pregnancies by the point at which this article was composed.

4. Discussion

In this prospective study, we analyzed 409 infertile patients with unilateral ovarian endometrioma who underwent ART before any surgical intervention. We compared the ART outcomes between healthy and affected ovaries. Healthy ovaries yielded more M2 oocytes and total embryos, while the number of follicles and high‐quality embryos (grades A and B) was similar in both groups. Endometrioma size did not affect ART outcomes. However, patients with AMH levels > 3 ng/dL produced more embryos and M2 oocytes than those classified as normal or poor responders, although the count of high‐quality embryos (Grades A and B) remained consistent across all three groups in the affected ovary.

This study represents the first comprehensive analysis examining the outcomes of in vitro fertilization (IVF) specifically in patients who present with endometriomas, while also making a clear comparison between the functioning of healthy ovaries and those that are affected by this condition. It employs a substantial sample size, allowing for a thorough evaluation of how pelvic and ovarian inflammatory mediators can influence assisted reproductive technology (ART) outcomes. This approach goes beyond the traditional focus, which typically emphasizes pregnancy rates and overall outcomes as the primary indicators of success in ART procedures. In contrast, this research aims to delve deeper into the underlying factors that might contribute to the results, providing a more nuanced understanding of ART success. Furthermore, it is important to note that previous investigations in this area have frequently overlooked the role of male factors that could significantly impact the quality of the eggs, often treating the assessment of oocytes quality in isolation rather than considering it within the broader context of ART. This oversight highlights the need for a more integrated approach to evaluating the myriad factors influencing reproductive outcomes in ART patients.

This study's limitations include the lack of differentiation between patients based on endometriosis severity based on surgical staging, as well as the absence of separate egg transfers from affected and healthy ovaries and followed their pregnancy outcomes.

In 2022, Kamath and colleagues analyzed the pregnancy outcomes of 758 endometriosis patients using oocyte donors compared to 12 858 autologous ART cycles from 1996 to 2016. Most patients were from after 2011, with the majority of transfers occurring in Fresh cycles. Although the study did not specify the types of endometriosis or prior surgeries before transfer, there was no significant difference in live birth rates (LBR) between the two groups, suggesting that endometriosis has no impact on embryo quality [19].

In 2017, Cardamon et al., compared live birth rates as the primary outcome and clinical pregnancy rates, oocyte counts, and fertilization rates as secondary outcomes in IVF and ICSI cycles involving 3583 endometriosis patients and 18 833 patients with tubal factor infertility. Although endometriosis patients had a lower number of retrieved oocytes (p < 0.001) and higher cancellation rates (3.94% vs. 2.95%. p = 0.005), their fertilization rates were similar to those of the tubal factor group (p = 0.159). After adjusting for paternal age and the number of transferred embryos, the live birth rates were also comparable between the two groups. The study further did not classify endometriosis types, and analyze eggs and embryos quality separately [10].

In 2021, Camile Rubin and his team studied IVF outcomes in 596 infertile patients: 175 with endometriosis across 348 cycles, yielding 2016 mature oocytes, and 401 with non‐endometriosis causes in 576 cycles, resulting in approximately 4073 mature oocytes. They assessed quality and morphology of oocytes using average oocytes quality index (AQQI) and morphological scoring system (MOMS) factors, finding no significant differences between the groups. While the endometriosis group produced fewer mature oocytes, embryos, and high‐quality embryos, these differences were not statistically significant. In their cohort, 165 endometriosis patients received pre‐treatment with GNRH_a, while 167 underwent endometriosis surgery. In our prospective study, all patients had endometrioma and had not undergone surgery or received pretreatment [15].

In 2019, Orazov et al. investigated IVF outcomes in 50 infertile patients with unilateral endometrioma post‐surgery, comparing them to 30 patients with tubal factor infertility. The results indicated that the health of the ovaries in the endometriosis group was adversely affected by the surgery, and this group was older than the control group (31.73 vs. 33.36 years). Despite similar total oocytes retrieval numbers in both groups, the endometriosis group had higher MI and GV oocytes compared to the control group, which also demonstrated poorer in vitro maturation ability than those from the control group [20].

Filipe and his colleagues examined the quality and quantity of oocytes and embryos from the affected ovary by unilateral endometrioma, comparing them to the healthy ovary in 29 infertile endometriotic patients. In their findings, both ovaries (affected and non‐affected) showed similar IVF results. They conducted 25 transfers: 10 from affected ovaries and 15 from healthy ones, with implantation rates of 40% and 22%, respectively, which was not statistically significant. The study didn't exclude patients with a history of endometriosis surgery (n = 3), infertility due to concomitant male factors infertility (n = 16), or those who had received pretreatment with OCP or progesterone (n = 8), and all participants had endometriomas smaller than three centimeters (25 ± 9 mm) [16].

In their retrospective study, Li et al. compared four groups regarding the number of follicles, oocytes, and M2 in frozen–thawed IVF cycles: endometrioma cystectomy (n = 224, FET cycle = 205) and endometrioma aspiration (n = 139, FET cycle = 148), DIE (n = 96, FET cycle = 89), and tubal factor infertility (n = 360, FET cycle = 474) groups. Their findings revealed that the M2, viable embryo, and clinical pregnancy rates in the endometriosis groups were lower than those in the tubal factor group. Furthermore, the DIE group's results were even worse than those of the endometrioma groups, while cystectomy outcomes were inferior to those of aspiration. Although pregnancy outcomes were similar among the three endometriosis groups, they were still lower than in the control group, which had a cumulative pregnancy rate of 56.9% compared to 75.3% in the DIE and tubal factor groups, with no significant differences among the aspiration (57.0%) and cystectomy (57.6%) groups. Notably, the DIE group had the fewest transition cycles, potentially biasing the results for this group [21].

This research is essential for accurately measuring how endometriosis and pelvic inflammatory conditions affect egg quality and quantity, ultimately leading to a more precise understanding of infertility in these endometriotic women. As a result, the presence of endometrioma in the affected ovary is associated with a decrease in the MII and total fertilization rate. However, the healthy ovary shows a higher number of Grade C embryos compared to the affected one, with no significant difference in high‐quality embryos between the two groups without any correlation with endometrioma size. Thus, in the hands of an expert, the presence of endometrioma during ART procedures does not decrease the quality or quantity of high‐quality embryos. These findings should be interpreted cautiously, and future research is needed to validate them using homogenous cohorts regarding demographic characteristics, AMH levels, and the extent of pelvic endometriosis. Future studies should also compare ART results between operated and non‐operated ovaries and assess the impact of deep infiltrating endometriosis (DIE) on these outcomes.

Disclosure

We did not use artificial intelligence for producing this article.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

Study data can be shared electronically through the corresponding author's email if necessary.