There are anywhere from 100 to 600 million sperm in every teaspoon of semen. You need just one to make it to the right place – the correct fallopian tube – at the correct time – after ovulation – to create a new life.
This makes it seem like pregnancy could occur very easily. It often does, of course, but most sperm die before making it to their final destination. Understanding how long sperm live – inside and outside the body – can help whether you are trying to get pregnant or trying to avoid getting pregnant.
Sperm cells have a limited life cycle. Some sperm die within a few minutes. A few might live up to seven days, but only under perfect conditions.
A sperm’s life cycle outside the man’s body begins at the moment of ejaculation.
Its goal is to swim through a woman’s cervix, make it through the uterus and end in the fallopian tube in search of an egg. It won’t have much time. During this process, sperm cells face many obstacles, and each one reduces the number of sperm. Out of the half-million sperm that started out, only about 10-20 will actually reach the woman’s egg – if there even is one available at that time.
When a sperm ends up outside of the woman’s body, it lives only a few minutes. Sperm needs moisture and warmth to live, so once exposed to air they quickly die. As soon as semen dries, the sperm within it dies.
This might lead to the idea that “pulling out” before ejaculation can prevent a pregnancy, but that isn’t always the case. Pre-ejaculation fluids can contain sperm and can be left inside the vagina. Semen that is close to the vagina where there is warmth and moisture can live up to 20 minutes and can still make it inside. The pull-out method of birth control isn’t usually effective.
Because sperm need moisture and warmth to survive, it is possible for sperm to live when ejaculation occurs in a bath or hot tub. Still, the chances of becoming pregnant in this way are very slim. The ratio of water to sperm is quite high and the chances of a sperm making it through the water and into the vagina is low. Besides, any chemicals, soap or suds in the water are likely to kill the sperm.
During vaginal intercourse, sperm is deposited in the acidic vagina. This atmosphere kills the sperm that don’t make it to the cervix within hours. During ovulation, the pH of the reproductive tract becomes less acidic and sperm might live a little longer, giving them extra time to swim upward toward the cervix.
Sperm that make it to the cervix and uterus have a longer life. They can live there up to five days, although most will die within one to two days. Here cervical fluids work to propel the living sperm through the uterus and into a fallopian tube. Some experts believe that the cervical fluid acts as a filter – allowing the most motile sperm through while stopping less mobile sperm.
Finally, some sperm make it to a fallopian tube. Although a few thousand might make the complete journey there, only a few will find an egg. The rest die during the search. The average life of a sperm that makes it to the fallopian tube is three to four days, although some can live as long as a week.
There are some factors that can shorten the average lifespan of a sperm cell:
- Air pollution
- Illicit drug use or some medications
- Anabolic steroids
- Being overweight
There is one way where a sperm can live indefinitely: freezing. This is done when someone wants to save sperm for later use through in vitro fertilization, artificial insemination or anonymous donation to a sperm bank.
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Eileen Bailey is a freelance health writer. She is the author of What Went Right: Reframe Your Thinking for a Happier Now, Idiot’s Guide to Adult ADHD, Idiot’s Guide to Cognitive Behavioral Therapy, Essential Guide to Overcoming Obsessive Love, and Essential Guide to Asperger’s Syndrome. She can be found on Twitter @eileenmbailey and on Facebook at eileenmbailey.