This cross-sectional study was conducted at the Reproductive Endocrinology and Invitro Fertilization (REI) unit of our hospital, following the approval of the hospital's ethics committee. Patients who underwent gonadotropin-releasing hormone agonist (GnRHa) treatment were enrolled in the study. During oocyte retrieval, follicular fluids of mature follicles (≥18 mm) were collected and pooled for each patient. The thiobarbituric acid method was used for the sialic acid levels and the absorbance values were measured by a spectrophotometer at 549 nm.

This cross-sectional study was conducted at the Reproductive Endocrinology and Invitro Fertilization (REI) unit our hospital, following the approval of the hospital's ethics committee. The inclusion criteria were as follows; under 40 years of age, normal thyroid and prolactin hormone levels, a basal follicle stimulating hormone (FSH) level <10 mIU/mL, BMI of 19-30 kg/m2. Exclusion criteria: a history of ovarian surgery, endometriosis, uterine anomaly, any endocrine disease including congenital adrenal hyperplasia, smokers, use of any medications and hormones in the last 3 months. Before the IVF treatment serum follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), thyroid-stimulating hormone (TSH), and estradiol (E2) levels were measured on the third day of the cycle. Age, body mass index, duration of stimulation, duration of infertility, the total dose of gonadotropins, E2 on the day of hCG administration, number of oocytes retrieved, fertilization rate, and pregnancy rate were recorded.

All patients underwent gonadotropin-releasing hormone agonist (GnRHa) treatment. Oocyte retrieval was done 36 hours after the hCG injection and ICSI was used for all patients. Embryo transfer was performed 48-72 hours after the oocyte retrieval.

During oocyte retrieval, follicular fluids of mature follicles (≥18 mm) were collected from the first follicle entered and were aspirated for each patient. Follicle aspirates, which were not clear and contaminated with blood, were excluded. Total and free sialic acid levels were measured in the follicular fluid.

Inclusion Criteria:

• under 40 years of age,
• normal thyroid and prolactin hormone levels,
• a basal follicle stimulating hormone (FSH) level <10 mIU/mL,
• body mass index (BMI) of 19-30 kg/m2

Exclusion Criteria:

• a history of ovarian surgery, endometriosis, uterine anomaly,
• any endocrine disease including congenital adrenal hyperplasia,
• smokers,
• use of any medications and hormones in the last 3 months.