Retrieval of an oocyte from a follicle relies on the release of the cumulus-oocyte-complex (COC) from the follicular wall into the lumen, thereby allowing aspiration by a needle. Flushing the follicle with multiple aspirations from the same follicle is used as a means to increase the ratio of COC per aspirated follicle. Data showed that follicular flushing is not superior to direct aspiration either in normally responding patients or in poor responders undergoing in vitro fertilization (IVF). There is no data in the literature regarding the issue in patients with mono-follicular growth. Direct aspiration or repeatedly flushing the follicle for those with a single follicle will be investigated.

Oocyte retrieval procedure This study aims to evaluate the effect of follicular flushing during oocyte retrieval procedure in patients with only one follicle. Double lumen needle will be used and direct follicular aspiration without flushing will be performed for all patients. If an oocyte will be obtained, the patient will be assigned to group A. If not, at least 1 course of follicular flushing will be used until retrieval of an oocyte and the patient will be assigned to group B.

Inclusion Criteria:

• women aged 18-40 years
• primary infertility
• diminished ovarian reserve with single mature follicle on the day of oocyte retrieval

Exclusion Criteria:

• natural cycle IVF
• presence of endometriosis/endometrioma(s)
• Absence of cumulus oocyte complex following oocyte retrieval
• Severe male factor infertility
• Pre-implantation genetic screening cycles

Women undergoing oocyte retrieval procedure due to primary infertility