Women are born with approximately 1 to 2 million eggs (oocytes) in their ovaries. This number is already reduced from a peak of about 6 to 7 million eggs while the female fetus is around 20 weeks old in the womb. The egg count declines steadily before birth to the 1 to 2 million range and continues to decrease throughout life
. By the time a girl reaches puberty, the number of eggs has dropped further to about 300,000 to 400,000. Over the reproductive years, only about 400 eggs are typically released during ovulation, while the rest gradually degenerate and are absorbed by the body. The egg count and quality decline with age, especially after the 30s, affecting fertility
