During the procedure of egg retrieval, sonography is used to guide a hollow needle directly into each follicle.

The follicular fluid in each follicle which contains each egg is aspirated. This procedure is called “follicle puncture”, “follicle fluid aspiration”, or “egg retrieval”.

The fluid is carried to embryology laboratory, where the egg is identified and isolated from the follicle fluid and placed in a dish that is filled with nutrient culture media and paraffin oil (mineral oil) for the purpose of sperm-egg fertilization.

Paraffin oil will float on the top of the nutrient culture medium to prevent the medium from evaporation and keep the medium composition in a stable condition.