Sperm FAQ
If it takes just one sperm and one egg to make a baby, why must men make so many sperm? And what number of sperm is considered normal? How long do sperm live? Can they live outside the body? Do men stop making sperm when they are older? Is there anything you can do to make more sperm or improve the health of your sperm?
WebMD takes a look at the facts about sperm and answers these and other frequently asked questions.
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How long do sperm live?
The answer depends on a number of factors, the most important of which is where the sperm are. On a dry surface, such as clothing or bedding, sperm are dead by the time semen has dried. In water, such as a warm bath or hot tub, sperm will likely live longer because they survive well in warm, wet environments; however, the chances sperm in a tub of water will find their way inside a female bather and cause her to become pregnant are extremely low.
In a woman's body, sperm can live for up to five days depending on the conditions, so if you have unprotected sex even a few days before your partner ovulates, there is a chance of achieving a pregnancy.
How many sperm do you need to achieve a pregnancy?
Technically it takes just one sperm to fertilize an egg and achieve a pregnancy, but for each sperm that reaches and fertilizes an egg, there are many millions that don't. The average ejaculation contains close to 100 million sperm and, according to the World Health Organization, men who have fewer than 20 million sperm per milliliter of semen may have difficulty conceiving.
Why do you need so many sperm if it takes just one to make a baby? Because the journey from the vagina to the fallopian tubes, through which the eggs travel from the ovaries to the uterus, is an arduous one that few sperm survive. For those that complete the trip, penetration of the egg is far from a sure thing. The egg is covered by a thick layer that makes fertilization more difficult. Experts believe this process may be nature's way of allowing only the healthiest sperm to fertilize the egg, thereby providing the greatest chances for a healthy baby.
Is there anything you can do to improve the health of your sperm?
Many of the things you do to keep yourself healthy can improve the health of your sperm, too. These include:
- Avoiding cigarettes and illicit drugs, especially anabolic steroids.
- Avoiding exposure to toxins such as pesticides and heavy metals.
- Limiting alcohol intake.
- Eating a healthy diet and maintaining a healthy weight.
Finally, it is important to take care to keep your scrotum cool, because heat slows sperm production. Avoid hot baths and hot tubs, wear boxers instead of briefs, and avoid pants that are tight or restrictive.
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