Insemination and IVF Fertilization
The morning of the egg retrieval, the male partner will be asked to provide a semen specimen. If conventional insemination is planned and the semen sample warrants, a drop containing hundreds of thousands of sperm will be placed with each egg. For men who have abnormal sperm counts or other abnormalities of sperm, or if the female partner has anti-sperm antibodies, intracytoplasmic sperm injection (ICSI) is used to aid fertilization. The day after insemination or ICSI, the eggs are examined for signs of fertilization.
Fertilization rates can be very confusing.
If conventional insemination is done, the fertilization rate in our practice averages 57%, which means that 57 out of 100 eggs fertilize on average with this method.
If ICSI is done, the fertilization rate averages 70%. This ICSI rate may be higher though, because only known mature eggs undergo ICSI. In conventional insemination, all eggs (even unknown immature eggs) are exposed to sperm and are included in the fertilization rate. Immature eggs will not fertilize. That means that immature eggs are excluded from the ICSI group and may artificially inflate the fertilization rate when compared to conventional insemination.
Your doctor will advise you on the insemination method best suited for your circumstances; please ask any questions you have about this complex topic. Keep in mind too, that these are averages, and individual patients’ fertilization rates, range from 0% to 100% (both of these extremes are rare).
Fertilized eggs (embryos) will develop in the culture dish within an incubator for up to six days (from the day of egg retrieval to the day of your day 3 or day 5 embryo transfer, and day 5 or day 6 embryo cryopreservation). You will be informed during this period about the progress of your eggs and embryos.
Embryos are cultured in media that supports their development. The media is formulated to provide different nutrients to the embryo based on the physiologic needs of the embryo at specific stages of development. The embryos on day five typically are at a stage of development called blastocysts and are ready for embryo transfer.