In some menstrual cycles, an egg does not mature, and a woman does not ovulate. This is known as anovulation. Anovulation may cause irregular menstrual cycles or no periods at all.
Anovulation disrupts women's menstrual cycles. This can cause problems such as infertility.
Some medications, conditions, and external factors that affect hormone levels can cause anovulation.
Sometimes, a woman may have one anovulatory cycle and then go back to a regular cycle. Other times, it is a chronic problem.
When anovulation occurs, a woman cannot get pregnant. For women who have completed menopause, this is quite normal.
Women of childbearing age do not usually experience anovulation unless something has disrupted the body's hormone levels or damaged the ovaries.
Women who ovulate regularly often see signs that occur during each cycle. They may experience the following:
- increased amounts of cervical mucus
- a drop and subsequent rise in resting body temperature in the middle of the menstrual cycle (around day 10-16)
- periods that occur regularly
Women with very irregular periods, or who do not see signs of ovulation, may wish to try an over-the-counter ovulation predictor kit. These kits measure levels of hormones in a woman's urine to determine when she is ovulating.
A doctor may also be able to test a woman's hormone levels or carry out an ultrasound scan to view the ovaries.
During anovulation, the ovaries do not produce fully matured eggs, and there is no ovulation. This prevents periods from occurring.
Some birth control methods contain hormones that are designed to stop ovulation and prevent pregnancy. They may include synthetic forms of the hormones progesterone and estrogen, and some contain only synthetic progesterone.
These types of birth control methods include:
- birth control pill - taken by mouth daily
- birth control patch - applied weekly to a particular part of the body
- vaginal ring - placed inside the vagina once a month
- birth control implant - inserted under the skin of the arm, lasting up to 3 years
- intrauterine device (IUD) with hormones - placed inside the uterus for 3 to 5 years
- birth control shot - given as an injection in the arm every 12 weeks
These drugs interfere with the ovaries' ability to grow and release an egg. As a result, the woman will have anovulatory cycles while taking the medication.
It is important to note that some IUDs contain copper rather than hormones. Copper does not cause anovulation; instead, it interferes with a sperm's ability to reach an egg.
Many packs of birth control pills contain 21 active tablets and seven placebo tablets. A woman who takes this type of birth control pill may still have a period during the week that she takes the placebo pills, although it is lighter than a regular period and is not caused by ovulation. Other methods may cause spotting or breakthrough bleeding.
Each method of birth control stops ovulation differently. Women should discuss their options with a healthcare provider to determine the best choice.
Side effects of drugs
Certain medications designed for other purposes can still stop ovulation. They include:
NSAIDs (non-steroidal anti-inflammatory drugs)
Herbs and natural remedies
Some herbs contain hormone-like substances that can disrupt ovulation. If someone is trying to get pregnant or is not ovulating regularly, they may wish to discuss any herbs or supplements they are taking with their doctor.
Skin creams and other topical products with hormones
Some products contain estrogen or progesterone that are designed to fight aging or help with problems such as premenstrual syndrome (PMS). These products can be absorbed into the body, causing anovulation or hormone imbalances.
Steroids are a type of hormone that can reduce inflammation. They can also interfere with the hormones needed for ovulation.
Cortisone and prednisone are common types of steroids that are prescribed for a variety of illnesses, such as allergies, lupus, asthma, and more. Topical steroids are used on the skin to treat inflammation and allergic reactions.
An article in the Annals of the Rheumatic Diseases found that half of the women who received a steroid shot had an irregular menstrual cycle afterward.
Epilepsy or seizure drugs
These medications may interfere with ovulation and the menstrual cycle, according to an article in the Journal of Human Reproductive Sciences.
Some epilepsy drugs may also cause congenital disabilities, so people taking these drugs should discuss pregnancy plans with their doctors.
If someone is trying to get pregnant and has not had success, they may wish to discuss their medications with a doctor. In some cases, the doctor can prescribe an alternative medicine or may consider a drug to encourage ovulation.
There is a higher risk of experiencing anovulation in women who exercise a lot, are stressed, or are underweight or overweight.
Certain health problems can interfere with the body's proper balance of the hormones that are critical to ovulation. These include conditions that affect the thyroid, adrenal, hypothalamus, and pituitary glands. All of these glands play a role in the delicate hormonal balance that leads to ovulation.
Polycystic ovarian syndrome (PCOS) affects up to 20 percent of women of childbearing age, according to the National Institutes of Health.
Fortunately, these hormone-related conditions are often treatable. Many women may be able to achieve ovulation with proper medical treatment.
Weight gain or loss may also be closely linked to ovulation as the hormone estrogen relies upon a healthy body weight for normal levels. A study in Human Reproduction found that women who were either very underweight or overweight had decreased estrogen levels, which can lead to anovulation and fertility problems.
Women who exercise excessively or who have high levels of stress may also experience anovulation because of disrupted hormone levels.
Anovulation may also occur with premature menopause, also known as premature ovarian insufficiency. A woman may be diagnosed with this if she stops ovulating before age 40.
The cause of premature menopause is often unknown, though some medications and conditions can cause it. Some women who are experiencing early menopause can be treated with medications to stimulate ovulation and achieve pregnancy.
Treatment and outlook
For many women, anovulation becomes an issue when they want to get pregnant, or they have irregular menstrual cycles.
Because many different factors influence a woman's hormones and menstrual cycle, there is no one solution for treating anovulation. In many cases, however, the underlying cause of anovulation or the issue that is affecting hormone levels can be diagnosed and treated. Treatment can lead to pregnancy or more regular menstrual cycles if desired.
If a woman suspects that she is not ovulating, she should see her doctor to explore any potential health problems and to work toward a healthy hormonal balance.