A woman is born with all the eggs she will ever have, typically around 1 to 2 million eggs at birth. During fetal development, this number is even higher, about 6 to 7 million eggs at around 20 weeks of gestation. By the time puberty begins, the number of eggs has decreased to approximately 300,000 to 500,000. This number continues to decline with age and menstruation, with about 1,000 eggs dying each month after puberty. By menopause, fewer than 1,000 eggs remain

. In summary:

• Fetus (around 20 weeks): 6 to 7 million eggs
• At birth: 1 to 2 million eggs
• At puberty: 300,000 to 500,000 eggs
• In 20s to early 30s: 150,000 to 150,000 eggs (declining)
• By late 30s (around age 37): about 25,000 eggs
• At menopause: fewer than 1,000 eggs remain

This decline is natural and irreversible, as women do not produce new eggs after birth