20. Egg Cells: Lifetime Supply
Unlike sperm, egg cells (oocytes) are present from birth. Females are born with their full supply, which can persist for decades. No new eggs are produced after birth, so the quantity and quality decline naturally with age.
This finite supply has profound effects on fertility and reproductive aging, ultimately influencing the timing of menopause. The longevity of egg cells is a key factor in women’s reproductive health. To learn more, visit Eunice Kennedy Shriver NICHD.