Impact of The Endometrioma on Ovarian Response and Pregnancy Rate in In Vitro Fertilization Cycles

At present, approximately 20-35% of all patients undergoing in vitro fertilization (IVF) are diagnosed with endometriosis (1, 2) among whom about 30-40% suffer from ovarian endometrioma (3, 4). The impact of ovarian endometrioma on assisted reproductive technologies (ART) results is a controversial issue. A previous meta-analysis (5) has shown reduced pregnancy rates in women with ovarian endometrioma who underwent IVF treatments when compared to patients with other infertility causes. However, other studies have not confirmed this finding (6-8). In addition, some studies have shown that ovarian endometrioma could adversely affect the number of oocytes retrieved (7, 9), oocyte quality, fertilization rate (5, 10), embryo quality and implantation rate (9, 11, 12). Kumbak et al. (13) have also reported poor embryo quality in patients with endometriosis; yet, there have been no effect on pregnancy rate. Other studies also found no adverse effect of ovarian endometrioma on pregnancy success rates (14-16).

Due to these conflicting results, the optimum management of ovarian endometrioma in IVF/ intra cytoplasmic sperm injection (ICSI) cycles is not clear (14, 17). Some authors believe that ovarian endometriomas should be removed before the IVF cycle (18); however, others have shown that excision of an ovarian endometrioma before an IVF cycle is likely to lead poor responses to ovarian stimulation and to impact fertility outcomes (19, 20).

The purpose of the present study was to evaluate the effect of ovarian endometriomas on ovarian response and IVF/ ICSI outcomes when compared to patients with mild male factor infertility.

This cohort study was performed at Royan Institute for Reproductive Biomedicine (Tehran, Iran) over a 24-months period between March 2005 and December 2007. We recruited a total of 104 women who were candidates for IVF/ICSI and fresh embryo transfers.

The study group consisted of 47 infertile women with either unilateral or bilateral ovarian endometrial cysts of less than 3 cm, based upon transvaginal sonographic diagnosis with diffuse low-level echoes without neoplastic or acute hemorrhage features. Patients had no histories of any ovarian surgeries. All ultrasound tests were performed by two expert technicians using an EUB 6000 (HI- TACHI, Japan) equipped with a 6 MHZ curvilinear color doppler probe. Technicians performed trans-vaginal ultrasounds between days 1 and 8 of the cycle, before starting ovarian stimulation. The location and dimension of the endometriomas were recorded at this time.

Patients with endometriomas larger than 3 cm underwent endometriotic cystectomy, via laparoscopic surgery. These patients were not included at the study. There was no patient with cystectomies, defined as a laparoscopic surgery applied for women with small ovarian endometriomas.

The control group consisting of 57 patients with mild male factor infertility was candidate for ICSI treatment during the same time period as the study groups. Mild male factor infertility was defined as the presence of at least 1 million motile sperm after processing.

All patients in both groups had indications for IVF/ICSI treatments, without any previous attempts.

Exclusion criteria for both groups were as follows: i. previous history of any systematic disease or malignancy, ii. basal follicle-stimulating hormone (FSH) more than 15 mIU/ml, iii. history of three or more unsuccessful IVF attempts, and iv. ovarian endometrioma less than 3 cm.

The study was approved by the Ethics Committee of Royan Institute for Reproductive Biomedicine. A written informed consent was obtained from all individuals before participation.

Stimulation protocol for all patients was according to the standard long protocol. All patients underwent oral contraceptive suppression starting from the 2^nd or 3^rd day of the menstrual cycle. Gonadotropin-releasing hormone agonist (GnRH agonist) suppression with Busereline (500 µg, Suprefact; Aventis Pharma Deutshlan, Frankfurt, Germany) was performed via subcutaneous injection starting on the 21^st day of the menstrual cycle. We began gonadotropin stimulation 14 days after subcutaneous GnRH agonist injection with daily dose of 150 IU of recombinant FSH (Gonal F; Serono, Geneva, Switzerland). The dose and duration of FSH treatment were adjusted by monitoring follicular development using ultrasound and estradiol levels. In both groups, gonadotropin stimulation continued until 2-3 follicles with a mean diameter of ≥17 mm were achieved. Then, 10000 IU of human chorionic gonadotropin (hCG; Choriomon; IBSA, Lugano, Switzerland) was administered, while oocyte retrieval was performed 34-36 hours later by a skilled gynecologist. Only normal follicles were punctured at the time of oocyte retrieval. During the procedure, every effort was made to avoid puncturing the endometrioma. If endometriomas were accidentally punctured, the procedure was interrupted and resumed after the needled was changed.

Metaphase II (MII) oocytes were injected using ICSI procedure. Normal fertilization was confirmed when two distinct pronuclei were present within 16-18 hours following oocyte injection.

The baseline characteristics including age, duration of infertility, and basic concentrations of E₂ and FSH level were similar between two groups (Table 1).

The mean number of retrieved oocytes in patients with endometrioma and in control group were 6.6 ± 3.74 vs. 10.4 ± 5.25, respectively (p<0.001). As seen in table 2, the numbers of MII oocytes were significantly lower in patients with endometrioma (5 ± 3.21) as compared to the control group (8.2 ± 5.4).

The thickness of the endometrium, follicle numbers and good quality embryos (grades A or B) were also comparable between the two groups (p>0.05). Both groups had similar implantation and pregnancy rates (Table 2). However, patients with endometrioma had higher gonadotropin consumption as compared with the control group. We had no severe ovarian hyperstimulation syndrome (OHSS) in both groups.

In patients with unilateral endometrioma, we compared outcomes between the affected ovary and healthy contra lateral ovary. There were no significant differences in terms of main outcome measures between the normal and involved ovaries (Table 3).

In the present study, the number of retrieved oocytes and MII oocytes were significantly lower in endometrioma patients than the controls; however, the number of good quality embryos (per MII injected oocyte) was comparable in both groups.

These results were consistent with previous investigations that found a lower ovarian response to gonadotropin stimulation in patients with endometrioma (13, 22). Al-Azemi et al. (23) have reported that ovarian endometrioma led to a decreased response to gonadotropins, as reflected by the smaller number of retrieved oocytes, which was also shown in our study.

Pellicer et al. (24) have demonstrated that endometriosis caused poor quality oocytes and embryos with decreased ability for implantation. Different mechanisms such as changes in autoimmune factors, cytokines or production of growth factors, increased rate of granulosa cell apoptosis, and decreased steroid levels were considered as negative factors for follicular growth and oocyte maturity in these patients (25, 26).

Although some studies have reported poor IVF-embryo transfer (ET) outcomes with endometriosis (9, 11, 12), we could not find any negative impact of ovarian endometrioma on clinical pregnancy and implantation rates. Some scholars have also shown that the existence of endometrioma did not influence embryo implantation, and have proposed that the detrimental effects were limited to the fertilization phase (27).

In patients with unilateral endometrioma, the presence of endometrioma at the time of aspiration did not compromise our ICSI outcomes. This result was in accordance with the study of Almog et al. (28) in which they found a similar number of antral follicles and oocytes retrieved from the affected and healthy contra lateral ovaries. It seems that in women with unilateral disease, the contra lateral intact ovary compensated for ovarian function and fertility potential (14). In the present study, we did not include patients who had surgery for their endometriosis. Additional studies are required to evaluate the effect of surgery.

Despite the lower response to gonadotropins in endometrioma patients, the rates of pregnancy and implantation rates, embryo quality, total number of embryos transferred per patient and fertilization of MII oocytes were not affected by the presence of the endometrioma. It seems that endometrial receptivity in two groups was similar. However, in consideration of the higher cancelling rate, the prognosis for patients with endometrioma was worse than in patients with male associated infertility.