An important aspect of fertility and pregnancy is sperm, and the lifespan of sperm after ejaculation completely depends on where it's living. How long sperm live depends on where the sperm are deposited. Sperm inside the vagina can live within cervical mucus or the upper genital tract for three to five days, allowing fertilization to occur so long as the sperm are living.
A lot of numbers are thrown out there about the lifespan of sperm but here's the scoop: sperm can live as little as a couple of hours or as long as five days after sex. Once inside the vagina, the lifespan of the sperm depends on the woman's vagina, uterus, and fallopian tubes. Without fertile cervical fluid, sperm won't survive longer than a few hours inside the vagina or uterus if they make it that far.
Some die within minutes, and some can live anywhere up to seven days, under perfect conditions. But most live about two or three days inside the female reproductive system, according to USC Fertility. You need just one sperm to make it to the right place — the correct fallopian tube — at the correct time — after ovulation — to create a new life.
Sperm can live outside the body for varying amounts of time, depending on several factors, including the environment Ie: cervical mucus, where they end up… 9. This is an incredible feat compared to the brief lifespan of a mere few hours when no cervical mucus is present 24. This is part of why tracking cervical mucus is crucial to understanding your fertility.
The length of time they stay alive has a lot to do with environmental factors and how fast they dry up. If you ovulate shortly after you finish your period, the sperm may still be alive and can fertilize the egg. Learn more: Can you get pregnant if you have sex on your period?
Update: A previous version of this article contained quotes from an expert whose credentials are now in question. We have reached out to him for confirmation of those credentials and have not heard back. You can read Gizmodo's investigation hereand his response here. Most people with penises produce between 39 million to million sperm per ejaculation, according to the World Health Organization.
Ejaculated sperm remain viable for several days within a woman's reproductive tract or in nutritive liquid culture medium in a lab setting. Fertilization is possible as long as the sperm remain alive — at least five days. Mayo Clinic does not endorse companies or products.