Causes of Infertility in Women
A woman’s fertility naturally declines as she gets older and approaches menopause. Research has demonstrated that a woman’s fertility peaks in her early 20s and begins to slowly decline after that, with a more dramatic reduction occurring after age 35. This reduction is due to several factors including reduced egg quality, age-related hormone changes affecting ovulation and decreased function of the uterus.
Every woman is born with a finite number of eggs, and while almost 800 eggs are lost each month, usually only one makes it to a point where it is released by the ovaries for fertilization in a process called ovulation. This process relies on a delicate balance of hormones in her body. If the released egg is not fertilized by a man’s sperm, it breaks down along with blood and tissue from the lining of the uterus in a process called menstruation. If a woman is having infrequent or irregular menstruation, it may indicate that she is not ovulating properly.
One common contributor to ovulation disorders is polycystic ovary syndrome (PCOS), which affects 5 to 20 percent of women of childbearing age. PCOS is a hormonal imbalance with extra testosterone (“male hormone”), making it hard for an egg to develop to a size where it can be released. Women with this condition are told they have cysts on their ovaries, when in reality these aren’t usually worrisome cysts (being relatively small), but are just a fraction of the 800 eggs that would be lost naturally if her hormones were balanced. The hormonal imbalance in PCOS can lead to poor egg quality along with other side effects such as weight gain, acne and excessive hair growth.
Tubal Disease or Blockage
The fallopian tubes are a pair of thin tubes connecting the ovaries to the uterus. If a woman is affected by tubal disease, it means that one or both of her fallopian tubes are partially or fully blocked or damaged in some way. Blockages may be due to an infection, previous trauma such as surgery or abdominal disease, or a birth defect.
The blockage can prevent the woman’s released egg from arriving in the fallopian tube where fertilization by sperm takes place. It also can prevent transport of the fertilized egg (embryo) to the uterus (womb) and therefore stop pregnancy from occurring. Tubal damage is important beyond just whether sperm and egg can find each other—if tubes are damaged, this can prevent an embryo from traveling back to the uterus and can result in ectopic pregnancy.
Endometriosis is a chronic disorder in which the tissue that lines the uterus, called the endometrium, spreads outside of the uterus and onto surrounding pelvic tissues and organs. The tissue continues to behave as it would within the uterus, getting thicker and bleeding as it does during menstruation. This can cause significant pain and discomfort in addition to making it more difficult for a woman to conceive, particularly if the case is severe.
Uterine Fibroids, Polyps & Other Abnormalities
Female infertility may be caused by other problems with the uterus aside from endometriosis. These include fibroids, polyps and other abnormalities such as scarring and structural defects that can be present from birth. Abnormalities may also be caused by surgery or disease.
Among these problems, polyps are the most common, affecting up to 15 percent of women with infertility. Polyps are growths of the lining of the uterus that didn’t stop growing when they were supposed to. Though unlikely, they can progress to cancer and are often diagnosed and treated with hysteroscopy.
Uterine fibroids are also common, affecting 5 to 10 percent of women diagnosed with infertility. Fibroids are noncancerous growths from the muscle of the uterus, and they often do not cause any symptoms. They can make both conceiving and pregnancy more difficult, depending on their number, size, and location.
Lifestyle and Environmental Factors
A range of other factors can contribute to infertility in women. Because of the balance of hormones required for proper reproductive functioning, certain lifestyle habits and environmental factors may negatively impact a woman’s chances of getting pregnant. These include:
- Obesity and being overweight (particularly if ovulation stops)
- Being underweight (particularly if ovulation stops)
- Drugs & alcohol
- Environmental toxins such as lead or radiation from medical equipment.
Related Information: Fertility Testing for Women