A man's role in making a baby is complex. Not only does the man produce the sperm, but he must propel them into the woman's vagina and on to the uterus. Once there, the sperm must be robust enough to swim up the fallopian tube and rendezvous with an egg.

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Fertilization During each menstrual cycle, an egg is released by one of the ovaries ... << ENLARGE

Usually, this reproductive process works the way it's supposed to. If you're thinking about having a baby, assume that your reproductive system works properly. It may take a while, even up to a year. But you and your partner can take steps to boost your odds of conceiving.

Fertilization requires healthy sperm. Healthy sperm are well formed, agile and fast. You need at least 20 million sperm per milliliter of semen. If the sperm move slowly or are misshapen or don't swim in the right direction, you may have trouble conceiving.

Sperm are made in the testicles, which are suspended in the scrotum outside your body. This provides a lower temperature, which is better for sperm development. Normal internal body temperature is too high for sperm to develop normally.

Testicles constantly produce sperm. Fluids from the prostate gland and seminal vesicles mix with the sperm to form semen, which is stored in the seminal vesicles. During sexual intercourse, the penis ejaculates the semen. Sperm are only a small portion of semen, but a single ejaculation may contain from a quarter billion to 1 billion sperm. Each sperm has a long tail that propels it forward. Although many sperm are produced, only about 200 or fewer reach the egg in the fallopian tube.

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Male reproductive system The male reproductive system makes, stores and moves sperm. Testicles ... << ENLARGE

If you want to have a baby, you need lots of healthy and fast sperm. Here are some things that may boost your chances of conceiving. Talk with your doctor about what may improve your fertility and what might impair your fertility.

• Take vitamins and minerals. Talk with your doctor about what supplements you might take. Selenium, zinc and folic acid are trace nutrients important for optimal sperm production and function. Usually a daily multivitamin provides adequate intake of these. Vitamins C (500 milligrams a day) and E (200 to 400 international units a day) are antioxidants that may also improve sperm function.
• Eat a healthy diet, get plenty of rest and minimize stress. Eating a healthy diet, getting enough rest and minimizing stress help the production of hormones that affect the development of sperm and the production of testosterone in the testicles.
• Keep cool. To produce a lot of healthy sperm, the testes must be cooler than normal body temperature. That's why the scrotum, which holds the testes, hangs outside your body. To maximize the quality and quantity of your sperm, avoid saunas, steam rooms, hot tubs, whirlpools and hot baths. Contrary to what you may have heard, a man's choice of underwear probably has no bearing on his sperm production. Although researchers have found that heat impairs the production and development of sperm, boxer shorts offer no scientifically proven advantage over briefs.
• Ask your doctor about prescription and over-the-counter medications. Some medicines can slow or prevent the production of sperm. Your doctor needs to know what's going into your body. Don't stop taking prescribed medication without consulting your doctor. Chemotherapy, radiation therapy and genital urinary surgery may cause temporary or permanent infertility. If you will be undergoing any of these procedures, talk with your doctor about saving and freezing your sperm (semen cryopreservation).
• Limit your alcohol intake. Alcohol can affect both the quality and the quantity of sperm, can lower testosterone levels and can contribute to erectile dysfunction. Generally, have no more than one or two drinks a day.
• Don't smoke. Smoking may increase the risk of infertility and erectile dysfunction in men. The sperm of men who smoke one to two packs of cigarettes a day may be misshapen and move more slowly. Secondhand smoke can cause respiratory problems for your baby. If you don't want to harm your baby, now is the time to quit smoking.
• Don't take illicit drugs. Marijuana can decrease sperm density and motility and increase the number of abnormal sperm. Cocaine can contribute to erectile dysfunction, and amphetamines can stall sex drive.
• Avoid toxic substances. Avoid contact with potentially toxic chemicals and don't breathe toxic fumes or vapors. Follow label instructions when using pesticides, herbicides, paints, stains, varnishes, glues, organic solvents and heavy metals.

If you have questions about these recommendations, talk with your doctor.

If you and your partner have tried unsuccessfully for a year to conceive, see your doctor to discuss other possible problems.