Egg donation is a practice within assisted reproductive technology (ART) where a healthy donor undergoes a medical procedure to retrieve eggs for fertilization in a recipient. Because the process involves powerful hormone treatments, fertility specialists closely monitor it to maximize the chances of a successful outcome. The primary goal is to collect a sufficient number of healthy eggs to overcome the natural attrition that occurs during fertilization.
The Average Number of Eggs Retrieved
The number of eggs collected in a successful donor cycle is significantly higher than the single egg naturally released in a typical menstrual cycle. Most clinics aim to retrieve between 10 and 20 oocytes, though high-performing donors may yield up to 23 eggs. This elevated target range is necessary because not every egg will be viable for creating a pregnancy. The goal is to create multiple viable embryos for the recipient, ensuring sufficient embryos for both fresh and frozen transfers.
The Role of Ovarian Stimulation
Achieving a high egg yield requires controlled ovarian hyperstimulation. In a natural cycle, only one dominant follicle matures, but fertility specialists use injectable hormone medications, primarily gonadotropins (FSH and LH analogs), to prompt multiple follicles to mature simultaneously. This controlled stimulation recruits the cohort of follicles available in that specific cycle.
The donor self-administers these injections for about 7 to 12 days, depending on the protocol and her response. Throughout this period, the donor is closely monitored using transvaginal ultrasounds and blood tests to track the growth of the follicles and hormone levels, such as estradiol. Monitoring ensures the follicles are developing at a proper rate and helps prevent Ovarian Hyperstimulation Syndrome (OHSS), which is a risk when stimulating a high number of eggs. Once multiple follicles reach a mature size, usually around 17 millimeters, a final “trigger shot” of human chorionic gonadotropin (hCG) or a GnRH agonist is administered to induce the final stage of egg maturation before the retrieval procedure.
Factors Determining the Final Yield
Several biological factors and procedural choices influence the final count of eggs retrieved. The donor’s age is a primary consideration, as younger donors typically produce a higher quantity of eggs. The Anti-Müllerian Hormone (AMH) level, a blood test marker, reflects the donor’s ovarian reserve. Higher AMH levels generally correlate with a greater number of eggs retrieved during stimulation.
The Antral Follicle Count (AFC), determined by an ultrasound count of small resting follicles, also gives a direct snapshot of the ovaries’ potential for a given cycle. Fertility doctors use a combination of the donor’s age, AMH, and AFC to select the appropriate stimulation protocol and medication dosage. Adjusting the dosage of gonadotropins is a careful balancing act, as too little medication results in a low yield, while too much increases the risk of OHSS.
Assessing Egg Maturity and Quality
The number of eggs retrieved is often higher than the number usable for fertilization. After retrieval, an embryologist performs denudation, gently removing surrounding cells to determine the egg’s stage of maturity. Only eggs that have reached the Metaphase II (MII) stage, indicated by the extrusion of the first polar body, are considered mature and capable of successful fertilization. Immature eggs (GV or MI) are not ready for fertilization and are discarded. Therefore, the final count of viable, mature eggs is always lower than the total number retrieved.