How long do women’s eggs remain viable?

Women ovulate once every month. During the ovulation period, the ovaries release an egg (ovum). Engaging in sexual intercourse during this time significantly increases the chances of conception, as pregnancy fundamentally depends on the union of sperm and egg. However, both sperm and eggs have limited lifespans after release—so identifying the optimal window for conception is essential. Below, we explore how long an egg remains viable.

How Long Does a Woman’s Egg Remain Viable?

An egg typically remains viable for 1–2 days, with its peak fertilization capacity occurring within the first 24 hours after ovulation. In contrast, sperm can survive in the female reproductive tract for 2–3 days. Therefore, intercourse during the ovulation period offers the highest likelihood of conception, while the probability declines progressively the further it occurs from ovulation. The “fertile window” generally spans approximately 10 days—starting five days before ovulation and ending four days afterward. Outside this interval lies the relatively safer, less fertile period. During the ovulation period, having intercourse once daily is sufficient.

However, an egg’s lifespan is markedly shorter than that of sperm—typically lasting only 12–24 hours. Once the egg enters the fallopian tube, it must encounter sperm within this 24-hour window to achieve fertilization. If sperm and egg fail to meet during this critical timeframe, the egg loses its capacity for fertilization and degenerates. Consequently, conception is only possible if intercourse occurs within 1–2 days before or after ovulation—that is, around mid-cycle.

How Long Does It Take for Sperm and Egg to Combine?

How long does it take for sperm and egg to unite? During intercourse, a man typically ejaculates 200–400 million sperm. Most sperm are expelled from the vagina along with seminal fluid, while a small fraction actively propel themselves forward using tail movement, traversing the cervical canal and uterine cavity to ultimately reach their destination—the ampulla of the fallopian tube—where they await the egg.

From ejaculation to arrival in the fallopian tube, sperm require approximately 1–1.5 hours. Although most sperm are expelled from the vagina with semen, the alkaline nature of cervical mucus supports sperm motility. A subset of sperm rapidly advances toward the cervical canal, where they secrete proteolytic enzymes to dissolve cervical mucus. Uterine contractions and fallopian tube peristalsis triggered by intercourse further accelerate sperm transport. Sperm travel from the vagina to the fallopian tube ampulla in as little as several minutes, though the longest transit time may extend to 4–6 hours—with 1–1.5 hours being typical.

We hope the above information is helpful. Wishing you a joyful and fulfilling life!