Infertility is defined as trying to get pregnant (with frequent intercourse) for at least a year with no success. Female infertility, male infertility or a combination of the two affects millions of couples in the United States. An estimated 10 to 18 percent of couples have trouble getting pregnant or having a successful delivery.
Infertility results from female factors about one-third of the time and male factors about one-third of the time. The cause is either unknown or a combination of male and female factors in the remaining cases.
Female infertility causes can be difficult to diagnose. There are many available treatments, which will depend on the cause of infertility. Many infertile couples will go on to conceive a child without treatment. After trying to get pregnant for two years, about 95 percent of couples successfully conceive.
The main symptom of infertility is the inability to get pregnant. A menstrual cycle that's too long (35 days or more), too short (less than 21 days), irregular or absent can mean that you're not ovulating. There may be no other outward signs or symptoms.
When to see a doctor
When to seek help sometimes depends on your age:
- Up to age 35, most doctors recommend trying to get pregnant for at least a year before testing or treatment.
- If you're between 35 and 40, discuss your concerns with your doctor after six months of trying.
- If you're older than 40, your doctor may want to begin testing or treatment right away.
Your doctor may also want to begin testing or treatment right away if you or your partner has known fertility problems, or if you have a history of irregular or painful periods, pelvic inflammatory disease, repeated miscarriages, prior cancer treatment, or endometriosis.
Each of these factors is essential to become pregnant:
- You need to ovulate. To get pregnant, your ovaries must produce and release an egg, a process known as ovulation. Your doctor can help evaluate your menstrual cycles and confirm ovulation.
- Your partner needs sperm. For most couples, this isn't a problem unless your partner has a history of illness or surgery. Your doctor can run some simple tests to evaluate the health of your partner's sperm.
- You need to have regular intercourse. You need to have regular sexual intercourse during your fertile time. Your doctor can help you better understand when you're most fertile.
- You need to have open fallopian tubes and a normal uterus. The egg and sperm meet in the fallopian tubes, and the embryo needs a healthy uterus in which to grow.
For pregnancy to occur, every step of the human reproduction process has to happen correctly. The steps in this process are:
- One of the two ovaries releases a mature egg.
- The egg is picked up by the fallopian tube.
- Sperm swim up the cervix, through the uterus and into the fallopian tube to reach the egg for fertilization.
- The fertilized egg travels down the fallopian tube to the uterus.
- The fertilized egg implants and grows in the uterus.
In women, a number of factors can disrupt this process at any step. Female infertility is caused by one or more of the factors below.
Ovulation is the release of an egg from one of the ovaries. It often happens about midway through the menstrual cycle, although the exact timing may vary.
In preparation for ovulation, the lining of the uterus, or endometrium, thickens. The pituitary gland in the brain stimulates one of the ovaries to release an egg. The wall of the ovarian follicle ruptures at the surface of the ovary. The egg is released.
Finger-like structures called fimbriae sweep the egg into the neighboring fallopian tube. The egg travels through the fallopian tube, propelled in part by contractions in the fallopian tube walls. Here in the fallopian tube, the egg may be fertilized by a sperm.
If the egg is fertilized, the egg and sperm unite to form a one-celled entity called a zygote. As the zygote travels down the fallopian tube toward the uterus, it begins dividing rapidly to form a cluster of cells called a blastocyst, which resembles a tiny raspberry. When the blastocyst reaches the uterus, it implants in the lining of the uterus and pregnancy begins.
If the egg isn't fertilized, it's simply reabsorbed by the body — perhaps before it even reaches the uterus. About two weeks later, the lining of the uterus sheds through the vagina. This is known as menstruation.
Ovulation disorders, meaning you ovulate infrequently or not at all, account for infertility in about 1 in 4 infertile couples. Problems with the regulation of reproductive hormones by the hypothalamus or the pituitary gland, or problems in the ovary, can cause ovulation disorders.
- Polycystic ovary syndrome (PCOS). PCOS causes a hormone imbalance, which affects ovulation. PCOS is associated with insulin resistance and obesity, abnormal hair growth on the face or body, and acne. It's the most common cause of female infertility.
- Hypothalamic dysfunction. Two hormones produced by the pituitary gland are responsible for stimulating ovulation each month — (FSH) and luteinizing hormone (LH). Excess physical or emotional stress, a very high or very low body weight, or a recent substantial weight gain or loss can disrupt production of these hormones and affect ovulation. Irregular or absent periods are the most common signs.
- Premature ovarian failure. Also called primary ovarian insufficiency, this disorder is usually caused by an autoimmune response or by premature loss of eggs from your ovary (possibly from genetics or chemotherapy). The ovary no longer produces eggs, and it lowers estrogen production in women under the age of 40.
- Too much prolactin. The pituitary gland may cause excess production of prolactin (hyperprolactinemia), which reduces estrogen production and may cause infertility. Usually related to a pituitary gland problem, this can also be caused by medications you're taking for another disease.
Damage to fallopian tubes (tubal infertility)
Damaged or blocked fallopian tubes keep sperm from getting to the egg or block the passage of the fertilized egg into the uterus. Causes of fallopian tube damage or blockage can include:
- Pelvic inflammatory disease, an infection of the uterus and fallopian tubes due to chlamydia, gonorrhea or other sexually transmitted infections
- Previous surgery in the abdomen or pelvis, including surgery for ectopic pregnancy, in which a fertilized egg implants and develops in a fallopian tube instead of the uterus
- Pelvic tuberculosis, a major cause of tubal infertility worldwide, although uncommon in the United States
Endometriosis occurs when tissue that normally grows in the uterus implants and grows in other locations. This extra tissue growth — and the surgical removal of it — can cause scarring, which may block fallopian tubes and keep an egg and sperm from uniting.
Endometriosis can also affect the lining of the uterus, disrupting implantation of the fertilized egg. The condition also seems to affect fertility in less-direct ways, such as damage to the sperm or egg.
Uterine or cervical causes
Several uterine or cervical causes can impact fertility by interfering with implantation or increasing the likelihood of a miscarriage:
- Benign polyps or tumors (fibroids or myomas) are common in the uterus. Some can block fallopian tubes or interfere with implantation, affecting fertility. However, many women who have fibroids or polyps do become pregnant.
- Endometriosis scarring or inflammation within the uterus can disrupt implantation.
- Uterine abnormalities present from birth, such as an abnormally shaped uterus, can cause problems becoming or remaining pregnant.
- Cervical stenosis, a narrowing of the cervix, can be caused by an inherited malformation or damage to the cervix.
- Sometimes the cervix can't produce the best type of mucus to allow the sperm to travel through the cervix into the uterus.
Sometimes, the cause of infertility is never found. A combination of several minor factors in both partners could cause unexplained fertility problems. Although it's frustrating to get no specific answer, this problem may correct itself with time. But, you shouldn't delay treatment for infertility.
Certain factors may put you at higher risk of infertility, including:
- Age. The quality and quantity of a woman's eggs begin to decline with increasing age. In the mid-30s, the rate of follicle loss speeds, resulting in fewer and poorer quality eggs. This makes conception more difficult, and increases the risk of miscarriage.
- Smoking. Besides damaging your cervix and fallopian tubes, smoking increases your risk of miscarriage and ectopic pregnancy. It's also thought to age your ovaries and deplete your eggs prematurely. Stop smoking before beginning fertility treatment.
- Weight. Being overweight or significantly underweight may affect normal ovulation. Getting to a healthy body mass index (BMI) may increase the frequency of ovulation and likelihood of pregnancy.
- Sexual history. Sexually transmitted infections such as chlamydia and gonorrhea can damage the fallopian tubes. Having unprotected intercourse with multiple partners increases your risk of a sexually transmitted infection that may cause fertility problems later.
- Alcohol. Stick to moderate alcohol consumption of no more than one alcoholic drink per day.
If you're a woman thinking about getting pregnant soon or in the future, you may improve your chances of having normal fertility if you:
- Maintain a normal weight. Overweight and underweight women are at increased risk of ovulation disorders. If you need to lose weight, exercise moderately. Strenuous, intense exercise of more than five hours a week has been associated with decreased ovulation.
- Quit smoking. Tobacco has multiple negative effects on fertility, not to mention your general health and the health of a fetus. If you smoke and are considering pregnancy, quit now.
- Avoid alcohol. Heavy alcohol use may lead to decreased fertility. And any alcohol use can affect the health of a developing fetus. If you're planning to become pregnant, avoid alcohol, and don't drink alcohol while you're pregnant.
- Reduce stress. Some studies have shown that couples experiencing psychological stress had poorer results with infertility treatment. If you can, find a way to reduce stress in your life before trying to become pregnant.
- Limit caffeine. Research suggests that limiting caffeine intake to less than 200 milligrams a day shouldn't affect your ability to get pregnant. That's about one to two cups of 6 to 8 ounces of coffee per day.