Infertility does not have a single cause because successful pregnancy is a multi-step chain of events.
Simply described, pregnancy includes the following steps: A woman’s ovaries must be able to release a viable egg, which then must be able to travel down the fallopian tube. The man must be able to ejaculate, and his sperm must be able to travel to the fallopian tube. The sperm and egg must unite to fertilize the egg. The fertilized egg must attach to the inside of a receptive uterus (or implant) and be nurtured by the body to allow the fetus to develop and grow until it is ready for birth.
Problems with any of these steps can lead to infertility.
The cause of infertility can rest in the woman or the man, or can be from unknown factors or a combination of factors. In some cases, environmental factors can contribute to infertility. In other cases, genetic conditions or other health problems are the main cause of infertility.
Female infertility
As explained above, female fertility requires a variety of conditions to be successful. If even one of these conditions is not met, or is not met for the right amount of time, the pregnancy may either not happen or it may end before birth.
Most cases of infertility in women result from problems with ovulation. Some conditions affecting ovulation include premature ovarian failure, in which the ovaries stop functioning before natural menopause, and polycystic ovary syndrome (PCOS), in which the ovaries may not release an egg regularly or may not release a viable, healthy egg. Among women who have PCOS, even when a healthy egg is released and fertilized, the uterus may not be receptive to implantation of a fertilized egg, which results in infertility.
Other causes of infertility might include:
A woman’s risk for infertility can also be affected by certain lifestyle and environmental factors, including (but not limited to):
- Age
- Stress
- Poor diet
- Being overweight or underweight
- Smoking, drugs, and alcohol
- Medication
- Environmental toxins
- Genetic conditions, such as being a carrier of Fragile X syndrome
- Other health problems, such as sexually transmitted diseases
Male infertility
The male fertility process involves the production of mature sperm and getting the sperm to reach and fertilize the egg. Although it may seem to be a simpler process than female fertility, male fertility also requires many conditions to be met: the ability to have and sustain an erection, having enough sperm, having enough semen to carry the sperm to the egg, and having sperm of the right shape that move in the right way. A problem meeting any of these conditions contributes to infertility.
Like female infertility, male infertility can result from physical problems, such as testes that don’t make enough normal sperm, hormonal problems, and lifestyle or environmental factors, including (but not limited to):
- Age
- Stress
- Exposing the testes to high temperatures, which can affect the ability of the sperm to move and to fertilize an egg. For instance:
- Cryptorchism is a condition where the testes do not descend into the scrotum. Although it does not usually affect the ability to have and sustain an erection, cryptorchism means that the testes are still inside the body cavity, which has a higher temperature than the external scrotum.
- Tight underwear—For some men, wearing tight underwear can also increase the temperature of the testes.
- Smoking, drugs, and alcohol
- Medications
- Environmental toxins
- Genetic conditions, such as Klinefelter syndrome
- Other health problems
But, in some cases, health care providers cannot determine a cause for infertility in the man or woman. In addition, some known causes of infertility do not have any treatments
