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Many parts of your body must be running smoothly to conceive a baby and carry a pregnancy to term. The man must be producing healthy, motile (swimming) sperm in large enough quantities to fertilize an egg cell. The woman's cervical mucus must be at the right pH and consistency to help the sperm make the journey in the reproductive tract. The ovaries must release healthy eggs. Her fallopian tubes must be free of blockages. The uterine environment must be suitable for implantation of a fertilized egg. And the endocrine system must be secreting hormones in the right sequence and at proper levels for pregnancy to happen.
About one-third of infertility cases are caused by problems with the woman's reproductive system. Another third can be traced to the man. Of the remaining cases, male and female factors are at play, and in some cases, one partner has many problems interfering with fertility. About 20 percent of infertility cases don't have a known cause.
Female infertility factors
For women, the older you are, the more likely you are to have problems becoming pregnant and carrying a fetus to term. Fertility rates slowly decline after age 30 and drop sharply after age 35, mostly because the eggs decline in quality. Women are born with all the eggs they'll ever have. So as you age, your eggs age, too. Eggs of older women are more likely to have chromosomal abnormalities, which help account for the higher-than-average miscarriage and Down's syndrome rate among women in their late 30s and 40s. However, donor eggs from younger women make it possible for thousands of older women to give birth.
Aside from poor egg quality, several other conditions can cause female infertility. In many cases, the problems can be successfully treated surgically or medically, or bypassed through assisted reproductive techniques.
Here are the most common causes of infertility in women:
- Pelvic inflammatory disease (PID) is an infection of the reproductive tract that usually is caused by a sexually transmitted disease but can also stem from a miscarriage, abortion, childbirth or an intrauterine device (IUD). Among other things, PID can lead to blocked or damaged fallopian tubes.
- Ovulatory dysfunction means that a woman's ovaries are not producing eggs or that egg production has declined because of age, hormonal imbalances or other problems.
- Genetic disease, such as chromosomal abnormalities.
- Uterine fibroids can interfere with embryo implantation or fetal growth. At least 40 percent of women have these benign uterine tumors, or myomas.
- Endometriosis is a sometimes painful condition occurring when tissue from the uterine lining occurs abnormally in other areas of the pelvis.
- Diethylstilbestrol (DES), a synthetic estrogen, was given to some women who were at risk for miscarriage during the 1950s and 1960s. Women and men whose mothers took DES while pregnant with them are at high risk for certain reproductive tract cancers and menstrual irregularities. Many DES daughters have an abnormally shaped uterus that can lead to repeated miscarriages. DES sons are prone to cysts in their reproductive tract, undescended testicles and other fertility problems.
- Pelvic adhesions are usually caused by surgery or infection. Pelvic adhesions are actually scar tissue that forms between two or more internal organs. Infertility can occur when the adhesions attach to the ovaries or fallopian tubes.
- Polycystic ovarian disease is a hormonally based condition characterized by scanty or absent menstruation. The disease usually causes multiple cysts to form in the ovaries.
- Immunological infertility is sometimes diagnosed when the woman's immune system produces "anti-sperm antibodies" that attack her partner's sperm. Some men also make antibodies to their own sperm. Immunological infertility can sometimes be treated medically or with assisted reproductive techniques. The theory that immune system abnormalities cause miscarriages is controversial and needs more study.
Causes of male infertility
Some men produce either no sperm at all (azoospermia) or too few healthy sperm (oligospermia). Several medical conditions are known to cause these conditions, including:
- Varicocele is a major cause of male infertility and occurs when a vein that carries blood out of the scrotum dilates, much like a varicose vein in another area. As a result, a pool of blood forms around the testicles, raising the temperature of the scrotum. The elevated temperature hinders the maturation process of sperm, which develop best in an environment that is slightly cooler than body temperature.
- Prenatal diethylstilbestrol (DES) exposure occurs in some men whose mothers took DES to prevent miscarriage in the 1950s and 1960s. They may have a blockage of the vas deferens, one of the tiny tubes through which sperm must travel.
- Ductal blockages, as a result of an infection or congenital abnormality, may occur in the minute ducts that carry sperm from the testicles to the penis.
- Marijuana depresses sperm counts. (In women, marijuana inhibits the secretion of reproductive hormones.)
Increasing your odds of getting pregnant
You'll want to do everything possible on your own to get pregnant. Even if your self-help efforts fail, they can generate important information to help your doctor diagnose the problem and save precious time. Here are some techniques you can try:
- Chart your basal body temperature (BBT). Ask your gynecologist or pharmacist for a set of basal body temperature charts and a special thermometer, and use them to track your temperature throughout the month. Beginning on the first day of your period (day 1 of your menstrual cycle), take your temperature as soon as you wake up in the morning before you get out of bed. If your ovulation pattern is normal, your temperature will be about a half degree higher during the latter half of your menstrual cycle. The day that your temperature jumps that half-degree is the day that ovulation has occurred. On average, this happens on day 14, but your menstrual cycle may be longer or shorter than average. As soon as your temperature rises, the next 24 hours are probably the most fertile time of the month for you. If your BBT pattern remains flat throughout the cycle, it is likely that you have not ovulated that month. It is important to include at least three BBT cycles in any attempt to draw any conclusions about your ovulatory pattern. Stress, illness, certain medications and other factors can temporarily affect the menstrual cycle as well as a man's sperm count. If you need to consult an infertility specialist, bring all your completed BBT charts to your initial consultation.
- Use an ovulation prediction test. Several commercial urine-test kits are available without prescription to detect the surge of luteinizing hormone (LH) that spurs ovulation. Note on your BBT chart the day your test comes up positive. Your egg will remain viable for about 24 hours after ovulation.
- Notice changes that occur with ovulation. Some women experience a slight twinge in their lower right or left abdomen when they ovulate. Around the same time, you may notice that your cervical mucus (which can occur as a normal vaginal discharge) has become watery and copious.
- Have intercourse every other day. Waiting 48 hours between lovemaking sessions provides enough time for a new generation of sperm cells to reach maturation.
- Have intercourse during the middle of your menstrual cycle. Counting the first day of your last period as day 1, your most fertile days are days 11 to 18. Use your BBT chart as a guide.
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This article was reviewed and updated June 2007.
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