Menorrhea is the normal flow of blood from the uterus that women typically experience during reproductive years. It may also be known as menstrual flow or a menstrual period. Menorrhea typically happens at regular intervals about once a month, though each woman’s cycle may vary. There are also several syndromes that can cause changes in a woman’s menorrhea.
A woman’s first menorrhea is typically known as menarche. It usually begins around age 12, though it can occur a few years earlier or later. Menarche is generally considered the beginning of a woman’s reproductive years.
During her reproductive years, a woman’s fertility cycle begins with a period of rising estrogen, which helps build up the lining of the uterus to prepare for a possible pregnancy. At the height of estrogen levels, an egg is released by the ovaries and travels down the fallopian tubes toward the uterus. If the egg is fertilized by a sperm, it will usually implant in the lining of the uterus and begin a pregnancy. In cases where a woman does not become pregnant during that cycle, her estrogen levels will drop over about 12-16 days, at the end of which the uterine lining will be shed out through the vagina in the process of menorrhea.
Each period of menorrhea can vary in its length and intensity. In general, menstrual bleeding lasts about two to seven days and occurs about every 21 to 45 days during a woman’s reproductive years, but this may vary from cycle to cycle and woman to woman. A woman may have cycles that include light, moderate and/or heavy bleeding, though total blood loss is usually only about 1-1.5 ounces (about 29.6-44.4 mL).
Several problems can occur with menorrhea. One common problem, especially in young women, is dysmenorrhea. Dysmenorrhea refers to menstrual periods that are unusually uncomfortable, often including cramps in the lower stomach or back. It is often due to high levels of hormones called prostaglandins, which cause the uterus to contract to help push the blood out. In some cases, it may also be caused by problems in the reproductive tract, such as fibroids or endometriosis.
Another problem that sometimes occurs is menorrhagia. This is severe blood loss of more than about 2.75 ounces (about 81.3 mL) in a single menstrual cycle. It is much less common than dysmenorrhea, but it is often associated with similar painful cramping. Causes of menorrhagia can include hormonal imbalances and fibroids in the uterus.
In contrast to painful or excessive menorrhea, amenorrhea is the absence of any menstrual bleeding. A woman is considered to have amenorrhea if she does not start menarche by about age 15 to 16, or if she goes for three or more months without any menstrual bleeding. This condition can be caused by many factors, including exercising too much, eating too little, taking certain medications and experiencing high levels of stress.