After the follicular fluid enters the laboratory, the embryologist conducts a “search” for the eggs, which are then placed in the incubator. Fertilization is carried out by concentrated sperm 4-6 hours after receiving the eggs. For normal fertilization, approximately 50 thousand spermatozoa are used per egg cell. If the sperm parameters do not meet the requirements of standard IVF or previous IVF attempts were unsuccessful, the question of further treatment tactics (possibly ICSI or IVF using donor sperm) is discussed. The ICSI technique is used for the fertilization of mature eggs in case of insufficient spermograms of a spouse.
If it is difficult to obtain sperm on the day of puncture or no sperm in the ejaculate, a special procedure is provided – testicular biopsy.
Puncture day is considered the zero-day of embryo cultivation; the first day of cultivation is the day following the puncture. It is on this day that most of the eggs appear the first signs of fertilization. They are already noticeable in 16 – 18 hours after the connection of eggs with spermatozoa (insemination). Re-assessment of fertilization is carried out in 24-26 hours after insemination. Control of fertilization is carried out by the embryologist when viewing cups of cultured cells under a microscope.