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How long can an egg be fertilized after ovulation?

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Diagram of the menstrual cycle showing hormone levels, follicle development, and endometrial changes across 28 days. It highlights menstruation, ovulation, and the follicular and luteal phases, with labeled curves for estrogen, progesterone, FSH, and LH. — menstruation Cyclical changes during a woman's normal ovulatory menstrual cycle.

Following ovulation, a human egg remains viable and capable of being fertilized for a relatively short period, typically between 12 and 24 hours. If the egg is not fertilized within this timeframe, it begins to degenerate.12