Women are born with all the eggs they will ever have. The number of eggs changes as follows:
- At about 20 weeks of fetal development, a female fetus has around 6 to 7 million eggs (oocytes)
- By birth, this number decreases to about 1 to 2 million eggs
- At puberty, the number further declines to approximately 300,000 to 400,000 eggs
- After puberty, about 1,000 eggs are lost each month, but only around 400 eggs are actually released during a woman's reproductive lifetime, typically one per menstrual cycle
- By the mid-20s, a woman usually has around 150,000 to 300,000 eggs remaining, and by the early 30s, about 100,000 to 150,000 eggs
- By age 37, the average woman has roughly 25,000 eggs left, and menopause occurs when fewer than 1,000 eggs remain
In summary, women start life with millions of eggs, but this number steadily declines throughout life until menopause, when the egg supply is nearly depleted
