Egg donation is a voluntary medical process designed to yield a greater number of eggs than a natural reproductive cycle, which typically releases only one. This high yield is intentional because only a fraction of retrieved eggs will ultimately result in a viable pregnancy. The number of eggs retrieved is highly variable, depending on the stimulation protocol used and the donor’s unique biological response to the medications.
The Retrieval Target: Average Number of Eggs Donated
The medical goal for a successful egg donation cycle is to retrieve a high number of eggs, typically aiming for a range between 10 and 20. Data often indicates average retrieval numbers exceed 15 eggs, particularly for highly screened first-time donors. This ambitious target is set because a natural reduction, known as attrition, occurs at every subsequent stage of the process.
Not every collected egg will be mature enough for fertilization, nor will every mature egg successfully fertilize to form an embryo. Only a portion of resulting embryos will develop to the blastocyst stage or be chromosomally normal. Retrieving a high quantity provides a buffer against this expected attrition rate, thereby increasing the likelihood of creating multiple viable embryos. Having multiple embryos ensures a higher chance of success over several transfers and provides cryopreserved embryos for future pregnancies.
Optimizing Yield: The Role of Ovarian Stimulation
Achieving a high egg count requires controlled ovarian stimulation using a carefully calibrated regimen of injectable hormonal medications. This treatment involves administering gonadotropins, which are analogs of Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH). These medications recruit and mature multiple resting follicles simultaneously, preventing a single dominant follicle from taking over, as happens in a natural cycle.
The stimulation phase typically lasts between 10 and 14 days, during which the donor self-administers daily injections. During this time, the donor undergoes intensive monitoring at the fertility clinic, involving frequent transvaginal ultrasounds and blood tests. Ultrasounds track the growth of developing follicles, aiming for a diameter between 13 and 20 millimeters, while blood tests measure hormone levels like estradiol to gauge the response.
When the majority of follicles reach the optimal size, the donor receives a final injection, known as the “trigger shot.” This shot contains Human Chorionic Gonadotropin (HCG) or a GnRH agonist, mimicking the body’s natural LH surge to initiate the final maturation process. The egg retrieval procedure is precisely timed to occur approximately 35 to 36 hours after the trigger shot, just before the body would naturally ovulate the eggs.
Factors Determining the Final Count
Even with a standardized stimulation protocol, the final number of eggs retrieved varies considerably due to the donor’s inherent biological characteristics. The strongest predictor of the final count is the donor’s ovarian reserve, which is assessed through specific markers. These markers help physicians personalize medication dosage to optimize the outcome and prevent over- or under-stimulation.
Key Ovarian Reserve Markers
A key marker is the Anti-Müllerian Hormone (AMH), produced by small ovarian follicles; higher levels correlate with a greater number of available eggs. The Antral Follicle Count (AFC) provides a direct visual assessment of the ovarian reserve. The AFC is the number of small, resting follicles (2–10 millimeters) counted via transvaginal ultrasound at the start of the cycle.
A higher AFC count and AMH level strongly predict a more robust response to stimulation medications and a higher egg yield. While all donors are highly screened, minor variations in age still play a role, as egg quantity naturally declines over time. The individual genetic response to gonadotropins also introduces variability, meaning some donors respond more vigorously to the hormones than others, even with identical baseline metrics.