We hear this concern frequently on our Welcome Consults for Ovally: If I freeze my eggs, don’t I decrease the number of eggs I have available? Does freezing my eggs therefore lower my chances of conceiving naturally after freezing them, because I have fewer eggs? Luckily, the answer is no – egg freezing takes advantage of eggs that would’ve otherwise disintegrated, and the number of eggs you freeze in a typical cycle is really tiny compared to the number of eggs you have available.
At the beginning of each menstrual cycle, women have between 3-30 immature egg cells developing in their follicles, which are tiny fluid-filled sacs that each contain an immature egg cell. Even though 3-30 eggs begin developing at the start of each cycle, typically only one egg fully matures and is released from its follicle during ovulation. The remaining 2-29 eggs simply disintegrate. In addition, there are thousands of other egg cells that disintegrate and die off each month without ever beginning to mature. It turns out that women are already born with an incredible surplus of eggs (1-2 million!); by the time a girl hits puberty, she only has about 300-500k eggs left. This rapid decline in eggs continues until menopause, with typically only one egg reaching maturity every month.
Egg freezing and in-vitro fertilization take advantage of eggs that would otherwise disintegrate. By increasing your levels of follicle-stimulating hormones, you try to get more than one egg to fully mature during the treatment cycle. How many eggs develop during the ‘stimulation’ period of egg freezing or IVF depends on your ovarian reserve and responsiveness to the follicle-stimulating hormones (see another post on the number of eggs to expect). When the eggs have grown to be almost mature inside the follicles, a ‘trigger shot’ is administered to prevent the follicles from releasing the eggs so they can be collected directly from the follicles and subsequently frozen.