Making a baby is a complex process that's contingent upon four crucial steps:
- A woman and man each producing eggs and sperm
- Healthy fallopian tubes that allow the sperm to easily get to the egg
- Sperm's ability to fertilize the egg upon reaching it
- A fertilized egg's ability to attach to the uterus and continue developing normally
Infertility may result when there's a hiccup in one or more of these steps. Most infertility problems in men result from difficulty producing healthy sperm or from a glitch in the sperm's ability to reach and fertilize an egg.
Problems producing sperm: It takes just one sperm to fertilize one egg to make a baby, but the chances of any given sperm cell reaching and penetrating an egg are very slim. The more sperm released after ejaculation (a measure known as sperm count), the better your odds for conceiving. Men who have sperm counts of 10 million or less sperm per milliliter of semen may have more fertility problems than those with normal sperm counts (20 million or more sperm per milliliter of semen).
To make the long trek from your vagina all the way to the egg in your fallopian tube, sperm also need to be in tip-top shape -- those that are abnormally structured may not be able to go the distance or penetrate the egg once they do arrive.
Sperm production and quality problems may be due to a number of factors, including imbalances with testosterone or other hormones; abnormalities with the testicles; including a varicocele (a varicose vein in the testicle that may keep the temperature too warm to produce sperm normally); exposure to certain environmental toxins or chemicals; taking certain medications (like steroids); genetic conditions; certain infections, like sexually transmitted diseases chlamydia and gonorrhea; and cancer and its treatments like chemotherapy and radiation.
Problems with releasing sperm: Sounds obvious, but sperm need to be able to leave the penis in the first place in order to reach the egg -- and some male fertility problems result from issues or blockages that prevent that. These include sexual problems, like premature ejaculation or trouble maintaining an erection; retrograde ejaculation, where semen backflow into the bladder instead of out through the penis; and blockages in the testicles or tubes that carry sperm.
Men who've previously had a vasectomy -- a procedure that makes men sterile (as a form of birth control) by cutting the tubes that deliver sperm from the testicles to the penis -- also fall into this group. In one study of men seeking help for infertility, more than 50 percent were looking to reverse a vasectomy compared to only five percent of men who sought to reverse vasectomies 30 years ago.
Certain diseases or conditions make some of these factors more likely. For example, diabetes or problems with the bladder or prostate may affect retrograde ejaculation; men with cystic fibrosis often have problems with the vas deferens, the tube that transports sperm from the testicles to the penis.