Once the eggs are retrieved, they are incubated with sperm in specialized culture media. Typically, the partner’s sperm is collected shortly before or a few hours prior to egg retrieval.
1. Semen Processing
- The semen sample is liquefied at room temperature.
- It is then prepared to remove seminal fluid and select the most motile sperm.
2. Fertilization
1 to 4 hours after egg retrieval, the eggs—still surrounded by their follicular cells—are placed in culture with 100,000 to 150,000 motile sperm per milliliter.
3. Fertilization Check
- After 18 to 20 hours, embryologists examine the eggs to confirm fertilization.
- Successful fertilization is identified by the presence of two pronuclei (one from the egg, one from the sperm) inside the fertilized egg, which is now called a zygote.
