Many women have their menstrual periods once every month. That is because the normal menstrual cycle has an average length of 21 to 35 days, so women may expect to have 11-13 menstrual cycles in a year. These are just averages, and every woman may have different lengths of menstrual cycles. However, some women may become a little bit concerned when her expected menstrual period does not come on the approximate date or week they had anticipated. If it seems like the period has not come for about 40 days or longer, one may consider it a missed period (amenorrhea). For women who are married or sexually active, it may be the first sign of pregnancy and this could be verified by taking a home pregnancy test. However, women can also have a missed period but it may not be due to a pregnancy. There are many possible reasons for a missed period but not a pregnancy and the most common ones are discussed here.
Causes of Missed Period but not Pregnancy
A missed period or amenorrhea is usually caused by pregnancy. However, there are other causes of missed period not due to pregnancy.
A woman undergoes different natural stages in her life that may result in missed periods.
- Primary amenorrhea. A girl who has never started her menstrual cycles by the age of 16 is said to have primary amenorrhea, and this may be caused by a delay in puberty or some other developmental problem such as congenital absence of a uterus. This is not normal and medical consultation must be sought to get proper diagnosis and treatment.
- Secondary amenorrhea. A girl or woman who has started having menstrual cycles that suddenly stop or who experiences missed periods for at least three months, for some reason not due to pregnancy, is said to have secondary amenorrhea. This is usually due to hormonal imbalance or an abnormal change in the uterus. In women who have a history of irregular menstrual periods, not having menstrual cycles for nine months is considered secondary amenorrhea.
- Breastfeeding. Hormones that promote lactation in breastfeeding women also inhibit the normal menstrual cycle, resulting in missed periods. In mothers who breastfeed exclusively, amenorrhea may last until the time the baby starts feeding solid foods. However, in other women, menstrual periods may return sooner.
- Menopause. Menopause marks the end of a woman's monthly menstrual cycles and this is defined as the absence of menstruation for 12 months. This usually occurs between the ages of 40 to 50 years, and is the result of normal hormonal changes that lead to a decrease in a woman's fertility.
Some medications can cause missed periods. The most common cause of missed periods due to medications is the use of contraceptives. Oral contraceptives or birth control pills like Yaz, Seasonale, or Lybrel can affect the regularity of a woman's period and lead to missed periods or irregular menstrual flow. These newer pills can cause women to have no menstrual periods for several months in a row, compared to traditional birth control pills, which allowed one to have menstrual flow. Other forms of contraceptives like the injections (ex. Depo-Provera) or implants (ex. Implanon) can also lead to amenorrhea or irregular periods.
Other drugs that can cause missed periods but nor pregnancy include antipsychotic drugs, antidepressants, corticosteroids and chemotherapeutic drugs.
- PCOS. Polycystic ovary syndrome is a female endocrine problem that leads to their inability to ovulate and secrete relatively high levels of hormones that are sustained. Because of this, the normal menstrual cycle does not occur and an affected woman may have amenorrhea or irregular l periods.
- Pituitary tumors. A benign tumor in the pituitary gland can cause hormonal changes resulting in missed periods.
- Thyroid disorder. Disorders in the thyroid leading to underactive (hypothyroid) or overactive (hyperthyroid) gland could lead women to have amenorrhea by altering hormonal mechanisms controlling the menstrual cycle.
- Premature menopause. Although menopause normally occurs in women who are 40-50 years old, sometimes it may occur before the age of 40 because of ovarian failure and low estrogen levels. This condition, known as premature menopause, leads to symptoms of menopause, such as missed periods, and infertility.
Problems in the female internal sexual structures or anatomy may cause amenorrhea, and these include:
- Uterine scars. Scar tissues sometimes develop in the lining of the womb or uterus, after a procedure such as a cesarean section, uterine fibroid surgery, or D&C (dilation and curettage). Uterine scarring inhibits the normal formation and shedding of the inner lining of the uterus during the normal menstrual cycle and leads to light irregular bleeding or amenorrhea.
- Congenital absence of reproductive parts, such as the uterus is the cause of some girls not having menstrual periods.
- Obstruction of the vaginal opening. This structural abnormality prevents the menstrual flow from coming out of the vagina, although a simple surgical treatment to relieve the obstruction will result in normal menstrual flow.
- Excessive stress or extreme anxiety can negatively affect one's normal hormonal production, which is regulated by the hypothalamus, a part of the brain. This can cause one's period to be delayed or missed. However, menstrual cycles usually return to normal once the stress is relieved.
- Extreme weight changes, such as excessive weight loss or gain can affect hormone production as well, leading to temporary irregularities in menstrual cycles. Fat cells contribute to estrogen production, and any disruption or imbalance in body fat can cause a woman to stop ovulating and menstruating.
- Eating disorders such as anorexia or bulimia cause abnormal hormonal changes because of the loss of fat and extreme thinness. These conditions can affect normal ovulation and inhibit menstrual cycles, leading to amenorrhea.
- Exercising rigorously or excessively can lead to high-energy expenditure and loss of body fat, which can inhibit ovulation and menstruation.
Dealing with Missed Period
- Use a home pregnancy test - If this is your first time to miss a period, consider if it is possible that you are pregnant, and verify this by using a home pregnancy test. This test may be obtained from a pharmacy and is easy to perform at home. You may also want to consult a physician, especially if it is going to be your first pregnancy.
- Think about common causes - If you are not considering the possibility of pregnancy, but it is your first time to have a delay in your menstrual period, think about other possible causes, such as extreme stress, exercise, or weight changes that may contribute to your problem. You may also try to think about certain medications you are taking or other symptoms you are experiencing which may be related to the hormonal changes. These are the most common causes of missed periods but not due to pregnancy.
- Seek medical help - It is always best to consult a physician especially if you have missed more than one period for two or three consecutive months. To assist the health provider in the evaluation it is also recommended that you keep track of your menstrual cycle and other symptoms you are experiencing. The treatment will vary depending on the specific cause of amenorrhea, and some tests may be needed to establish a diagnosis.