Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term. There are many biological causes of infertility, including some that medical intervention can treat.
Women who are fertile experience a natural period of fertility before and during ovulation, and they are naturally infertile during the rest of the menstrual cycle. Fertility awareness methods are used to discern when these changes occur by tracking changes in cervical mucus or basal body temperature.
The cause or causes of infertility can involve one or both partners. In general:
- In about one-third of cases, infertility is due to a cause involving only the male partner.
- In another one-third of cases, infertility is due to causes involving both the male and female.
- In the remaining one-third of cases, infertility is due to a cause involving only the female.
Causes of male infertility
A number of things can affect sperm count, ability to move (motility) or ability to fertilize the egg. The most common causes of male infertility include:
- Abnormal sperm production or function due to various problems, such as undescended testicles, genetic defects or repeated infections.
- Problems with the delivery of sperm due to sexual problems, such as premature ejaculation or painful intercourse (dyspareunia); health issues, such as retrograde ejaculation; certain genetic diseases, such as cystic fibrosis; or structural problems, such as blockage of the part of the testicle that contains sperm (epididymis).
- General health and lifestyle issues, such as poor nutrition, obesity, or use of alcohol, tobacco and drugs.
- Overexposure to certain environmental factors, such as pesticides and other chemicals. In addition, frequent exposure to heat, such as in saunas or hot tubs, can elevate your core body temperature. This may impair your sperm production and lower your sperm count.
- Damage related to cancer and its treatment. Both radiation and chemotherapy treatment for cancer can impair sperm production, sometimes severely. The closer radiation treatment is to the testicles, the higher the risk of infertility. Removal of one or both testicles due to cancer also may affect male fertility.
- Age. Men older than age 40 may be less fertile than younger men.
- Causes of female infertility
The most common causes of female infertility include:
- Fallopian tube damage or blockage, which usually results from inflammation of the fallopian tube (salpingitis). Chlamydia, a sexually transmitted infection, is the most frequent cause.
- Endometriosis, which occurs when the uterine tissue implants and grows outside of the uterus — often affecting the function of the sperm, egg and ovaries, uterus, and fallopian tubes.
- Ovulation disorders, which can prevent the ovaries from releasing eggs (anovulation). Underlying causes may include injury, tumors, excessive exercise and starvation. In addition, some medications can be associated with ovulation disorders.
- Elevated prolactin (hyperprolactinemia), the hormone that stimulates breast milk production. High levels in women who aren’t pregnant or nursing may affect ovulation.
- Polycystic ovary syndrome (PCOS), a condition in which your body produces too much of the hormone androgen causing ovulation problems. PCOS is also associated with insulin resistance and obesity.
- Early menopause, which is the absence of menstruation and the early depletion of ovarian follicles before age 40. Although the cause is often unknown, certain conditions are associated with early menopause, including immune system diseases, radiation or chemotherapy treatment, and smoking.
- Uterine fibroids, which are benign tumors in the wall of the uterus and are common in women in their 30s and 40s. Rarely, they may cause infertility by blocking the fallopian tubes. More often, fibroids interfere with proper implantation of the fertilized egg.
- Pelvic adhesions, bands of scar tissue that bind organs after pelvic infection, appendicitis, or abdominal or pelvic surgery. This scar tissue formation may impair fertility.
Other causes in women
- Medications. Temporary infertility may occur with the use of certain medications. In most cases, fertility is restored when the medication is stopped.
- Thyroid problems. Disorders of the thyroid gland, either too much thyroid hormone (hyperthyroidism) or too little (hypothyroidism), can interrupt the menstrual cycle and cause infertility.
- Cancer and its treatment. Certain cancers — particularly female reproductive cancers — often severely impair female fertility. Both radiation and chemotherapy may affect a woman’s ability to reproduce. Chemotherapy may impair reproductive function and fertility in men and women.
- Other medical conditions. Medical conditions associated with delayed puberty or amenorrhea, such as Cushing’s disease, sickle cell disease, kidney disease and diabetes, can affect a woman’s fertility.