New Delhi, Oct. 25 -- A woman in her late 30s may still have regular periods and yet find that getting pregnant is taking longer than expected. It can be tempting to assume fertility will remain unchanged until periods become irregular. Still, the two don't follow the same timeline. Changes in the ovaries begin well before menopause, and they can affect the chances of conception while menstrual cycles still appear normal. This is partly because of a woman's egg supply. Unlike sperm, which is produced continuously, a woman's egg supply is finite. This supply declines over time, and the rate of decline varies.

What changes before menopause?

Two aspects of ovarian ageing are particularly relevant to fertility: ovarian reserve and egg quali...