If egg retrieval is performed too early, the eggs may be immature. If it is too late, ovulation may occur or the eggs may become overmature, reducing success rates. Therefore, timing is critical. In general, when follicles reach about 18 mm or larger, an hCG injection is given in the evening, and egg retrieval is performed approximately 35 hours later.The procedure is done under sedation. Using transvaginal ultrasound guidance, a needle is inserted through the vaginal wall to retrieve the eggs from the ovaries.
The procedure takes about 20–30 minutes, and patients can go home once they have recovered from sedation. Since the eggs are collected before ovulation, they require further maturation. They are cultured for a certain period in a laboratory environment that closely mimics the conditions inside the body before fertilization.