Causes of Infertility in Women
What Causes Female Infertility?
According to the World Health Organization (WHO) the most common identifiable factors of female infertility were:
- Ovulatory disorders – 25%
- Endometriosis – 15%
- Pelvic adhesions – 12%
- Tubal blockage – 11%
- Other tubal/uterine abnormalities – 11%
- Hyperprolactinemia – 7%
- Ovulatory Disorders – Ovulatory disorders are one of the most common causes of female infertility, affecting a quarter of all infertility cases. These disorders involve irregular or absent ovulation, which makes the release of eggs for fertilization inconsistent or impossible. Conditions such as Polycystic Ovary Syndrome (PCOS), hypothalamic dysfunction, and primary ovarian insufficiency fall under this category.
- Endometriosis – Endometriosis affects an estimated 15% of women dealing with infertility. It is a condition in which tissue similar to the lining inside the uterus (endometrial tissue) grows outside of the uterus, often affecting the ovaries, fallopian tubes, and the tissue lining the pelvis. This can lead to pelvic pain, irregular menstrual cycles, and infertility.
- Pelvic Adhesions – Pelvic adhesions, accounting for 12% of infertility cases, are bands of scar tissue that bind organs after pelvic infection, appendicitis, or abdominal or pelvic surgery. They can interfere with the functioning of the ovaries and fallopian tubes, thereby leading to fertility problems.
- Tubal Blockage – Tubal blockage contributes to 11% of infertility cases. This occurs when a blockage in the fallopian tubes prevents the sperm from reaching the egg for fertilization or prevents a fertilized egg from reaching the uterus for implantation. The blockage can be caused by a variety of factors, including pelvic inflammatory disease, certain sexually transmitted infections, and previous surgery in the abdomen or pelvis.
- Other Tubal/Uterine Abnormalities – Other tubal or uterine abnormalities constitute 11% of infertility cases. These may include physical abnormalities in the shape or structure of the uterus or fallopian tubes that can interfere with conception or carrying a pregnancy to term. Examples may include uterine fibroids, uterine septum, or congenital uterine anomalies.
- Hyperprolactinemia – Hyperprolactinemia is responsible for 7% of infertility cases. This condition is characterized by the excessive production of prolactin, a hormone the pituitary gland produces. High levels of prolactin can interfere with the ovulation process, leading to irregular or absent menstrual cycles, which can cause infertility.
How Age Factors into Female Infertility
As women age, fertility declines due to normal, age-related changes that occur in the ovaries. Unlike men, who continue to produce sperm throughout their lives, a woman is born with all the egg-containing follicles in her ovaries that she will ever have.
When it comes to the quantity and quality of eggs, women are on a continuum. 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.
Generally, as you age, the number of quality eggs you have in reserve diminishes.
- When you are in your 20s, 80-90% of eggs are chromosomally normal.
- As you get into the early 30s, maybe 2/3rds are good.
- And as you get to mid to late 30s, roughly 1/3rd are good quality.
- Certainly, by the 40s, it’s reduced to a quarter or less.
- By 45, you can even see 90-95% of eggs are chromosomally abnormal.
So, age is one of the most important aspects of calculating quantity vs. quality. The more eggs available, the more likely there is a good one in there. But, the older we get, the higher percentage of the eggs inside your ovaries contain genetic abnormalities.
Ovulation Disorders is a primary cause of female infertility
Most cases of female infertility are caused by problems with ovulation. Without ovulation, there are no eggs to be fertilized.
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.
PCOS is one of the most common causes of female infertility
Ovulation problems are often caused by polycystic ovarian 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.
Damage or Disease to the fallopian tubes can result in female infertility
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.
How Endometriosis increases risk of female infertility
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.
Endometriosis can influence fertility in several ways : distorted anatomy of the pelvis, adhesions, scarred fallopian tubes, inflammation of the pelvic structures, altered immune system functioning, changes in the hormonal environment of the eggs, impaired implantation of a pregnancy, and altered egg quality.
Endometriosis can cause scar tissue , cysts, and adhesions to form in and around your reproductive organs. This tissue can interfere with the conception process. When a mature egg is released from one of your ovaries, it’s supposed to travel through a fallopian tube and into your uterus. Scar tissue and ovarian cysts can make this journey impossible by:
- preventing the release of an egg
- preventing the fallopian tubes from picking up an egg
- blocking the fallopian tubes
Adhesions can also cause your ovaries to stick to your uterus, making it harder for the fallopian tube and ovary to connect. Scar tissue and lesions may also alter the shape of your uterine cavity. This may make it harder for an embryo (fertilized egg) to implant itself in your uterus.
Fibroids, Polyps & Uterine Abnormalities can female infertility
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 the most common tumor in women, and their prevalence is high in patients with infertility. Fibroids may be the sole cause of infertility in 2–3% of women. 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.
How Lifestyle and Environmental Factors impacts female infertility
A range of other lifestyle and environmental 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.
- Among women with obesity who have polycystic ovary syndrome (PCOS), losing 5% of body weight greatly improves the likelihood of ovulation and pregnancy.
- Being underweight is linked to ovarian dysfunction and infertility in women.
- Excessive exercise is known to affect ovulation and fertility in women.
- Substance use, including smoking tobacco, using other tobacco products, marijuana use, heavy drinking, and using illegal drugs such as heroin and cocaine, reduce fertility in both men and women.
- Radiation therapy and chemotherapy can cause infertility in females and males.
Related Information: Fertility Testing for Women