Women are born with a finite number of eggs and the egg reserve gradually declines throughout the reproductive years.
At birth, approximately 1-1.5 million eggs are present, which declines to half at puberty and down to about 25,000 at age 37. The initial drop is estimated to be at age 27 which may not be clinically relevant, but the second drop at age 35 is considered significant.
The drop in the egg reserve is asymptomatic and the rate of decline is mostly dependent on genetics. When there are no eggs left in the ovaries, there is no ovulation or menstrual cycles and the woman goes into menopause.
The eggs that aren’t ovulated all die naturally via a process called atresia. At this time, there aren’t any treatments to improve ovarian reserve or restore egg numbers.
Ovarian reserve is primarily determined by genetics, however some external factors such as prior ovarian surgery, some chemotherapy agents, pelvic radiation, and smoking can speed egg loss.