Menstruation

Menstruation is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. The menstrual cycle is characterized by the rise and fall of hormones. Menstruation is triggered by falling progesterone levels, and is a sign that pregnancy has not occurred. Feminine hygiene products are used in order to maintain hygiene during menses.
The first period, a point in time known as menarche, usually begins during puberty, between the ages of 11 and 13. However, menstruation starting as young as eight years would still be considered normal. The average age of the first period is generally later in the developing world, and earlier in the developed world. The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women; in adults, the range is between 21 and 35 days with the average often cited as 28 days. In the largest study of menstrual app data, the mean menstrual cycle length was determined to be 29.3 days. Bleeding typically lasts two to seven days. Periods stop during pregnancy and typically do not resume during the initial months of breastfeeding. Lochia occurs after childbirth. Menstruation, and with it the possibility of pregnancy, ceases after menopause, which usually occurs between 45 and 55 years of age.
During their menstrual period, 38% of all women reported not to be able to perform all their regular daily activities. Symptoms in advance of menstruation that do interfere with normal life are called premenstrual syndrome. Some 20 to 30% of women experience PMS, with 3 to 8% experiencing severe symptoms. These include acne, tender breasts, bloating, feeling tired, irritability, and mood changes. Other symptoms some women experience include painful periods and heavy bleeding during menstruation and abnormal bleeding at any time during the menstrual cycle. A lack of periods, known as amenorrhea, is when periods do not occur by age 15 or have not re-occurred in ninety days.

Characteristics

Length and duration

The first menstrual period occurs after the onset of pubertal growth, and is called menarche. The average age of menarche is 12 to 15 years. However, it may occur as early as eight. The average age of the first period is generally later in the developing world, and earlier in the developed world. The average age of menarche has changed little in the United States since the 1950s.
Menstruation is the most visible phase of the menstrual cycle and its beginning is used as the marker between cycles. The first day of menstrual bleeding is the date used for the last menstrual period. The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women, and 21 to 35 days in adults. The average menstrual cycle length is conventionally said to be 28 days. In the largest study using data from menstrual apps, the mean menstrual cycle length was determined as 29.3 days. The variability of menstrual cycle lengths is highest for women under 25 years of age and is lowest, that is, most regular, for ages 25 to 39 years. The variability increases slightly for women aged 40 to 44 years.
Perimenopause refers to the transitional phase leading up to menopause, marked by hormonal changes and irregular menstrual cycles, when a woman stops menstruating completely and is no longer fertile. The medical definition of menopause is one year without a period and typically occurs between 45 and 55 years in Western countries. Menopause before age 45 is considered premature in industrialized countries. Illnesses, certain surgeries, or medical treatments may cause menopause to occur earlier than it might have otherwise.

Menstrual fluid

The average volume of menstrual fluid during a monthly menstrual period is with considered typical. Menstrual fluid is the correct term for the flow, although many people prefer to refer to it as "menstrual blood". Menstrual fluid is reddish-brown, a slightly darker color than venous blood.
About half of menstrual fluid is blood. This blood contains sodium, calcium, phosphate, iron, and chloride, the extent of which depends on the woman. As well as blood, the fluid consists of cervical mucus, vaginal secretions, and endometrial tissue. Vaginal fluids in menses mainly contribute water, common electrolytes, organ moieties, and at least 14 proteins, including glycoproteins.
Many women and girls notice blood clots during menstruation. These appear as clumps of blood that may look like tissue. If there was a miscarriage or a stillbirth, examination under a microscope can confirm if it was endometrial tissue or pregnancy tissue that was shed. Sometimes menstrual clots or shed endometrial tissue is incorrectly thought to indicate an early-term miscarriage of an embryo. An enzyme called plasmin – contained in the endometrium – tends to inhibit the blood from clotting.
The amount of iron lost in menstrual fluid is relatively small for most women. In one study, premenopausal women who exhibited symptoms of iron deficiency were given endoscopies. 86% of them actually had gastrointestinal disease and were at risk of being misdiagnosed simply because they were menstruating. Heavy menstrual bleeding, occurring monthly, can result in anemia.

Hormonal changes

Side effects

Menstrual health overview

Moods and premenstrual syndrome (PMS)

Cramps

In most women, various physical changes are brought about by fluctuations in hormone levels during the menstrual cycle. This includes muscle contractions of the uterus that can precede or accompany menstruation. Many women experience painful cramps, also known as dysmenorrhea, during menstruation. Among adult women, 2%–28% have pain severe enough to affect daily activity. Severe symptoms that disrupt daily activities and functioning may be diagnosed as premenstrual dysphoric disorder. These symptoms can be severe enough to affect a person's performance at work, school, and in everyday activities in a small percentage of women.
When severe pelvic pain and bleeding suddenly occur or worsen during a cycle, this could be due to ectopic pregnancy and spontaneous abortion. This is checked by using a pregnancy test, ideally as soon as unusual pain begins, because ectopic pregnancies can be life‑threatening.
The most common treatment for menstrual cramps are non-steroidal anti-inflammatory drugs. NSAIDs can be used to reduce moderate to severe pain, and all appear similar. About 1 in 5 women do not respond to NSAIDs and require alternative therapy, such as simple analgesics or heat pads. Other medications for pain management include aspirin or paracetamol and combined oral contraceptives. Although combined oral contraceptives may be used, there is insufficient evidence for the efficacy of intrauterine progestogens.
One review found tentative evidence that acupuncture may be useful, at least in the short term. Another review found insufficient evidence to determine an effect.

Interactions with other conditions

Known interactions between the menstrual cycle and certain health conditions include:

Some women with neurological conditions experience increased activity of their conditions at about the same time during each menstrual cycle. For example, drops in estrogen levels may trigger migraines, especially when the woman who has migraines is also taking the birth control pill.
Many women with epilepsy have more seizures in a pattern linked to the menstrual cycle; this is called "catamenial epilepsy". Different patterns seem to exist, and the frequency with which they occur has not been firmly established.
Research indicates that women have a significantly higher likelihood of anterior cruciate ligament injuries in the pre-ovulatory stage, than post-ovulatory stage.
Sexual activity

Sexual feelings and behaviors change during the menstrual cycle. Before and during ovulation, high levels of estrogen and androgens result in women having a relatively increased interest in sexual activity, and relatively lower interest directly prior to and during menstruation. Unlike other mammals, women may show interest in sexual activity across all days of the menstrual cycle, regardless of fertility.
There is no reliable scientific evidence that would advise against sexual intercourse during menstruation based on medical grounds.

Fertility aspects

Peak fertility occurs during just a few days of the cycle: usually two days before and two days after the ovulation date. This corresponds to the second and the beginning of the third week in a 28-day cycle. This fertile window varies from woman to woman, just as the ovulation date often varies from cycle to cycle for the same woman. A variety of methods have been developed to help individual women estimate the relatively fertile and the relatively infertile days in the cycle; these systems are called fertility awareness.

Menstrual disorders

Infrequent or irregular ovulation is called oligoovulation. The absence of ovulation is called anovulation. Normal menstrual flow can occur without ovulation preceding it: an anovulatory cycle. In some cycles, follicular development may start but not be completed; nevertheless, estrogens will be formed and stimulate the uterine lining. Anovulatory flow resulting from a very thick endometrium caused by prolonged, continued high estrogen levels is called estrogen breakthrough bleeding. Anovulatory bleeding triggered by a sudden drop in estrogen levels is called withdrawal bleeding. Anovulatory cycles commonly occur before menopause and in women with polycystic ovary syndrome.
Very little flow is called hypomenorrhea. Regular cycles with intervals of 21 days or fewer are polymenorrhea; frequent but irregular menstruation is known as metrorrhagia. Sudden heavy flows or amounts greater than 80 ml are termed menorrhagia. Heavy menstruation that occurs frequently and irregularly is menometrorrhagia. The term for cycles with intervals exceeding 35 days is oligomenorrhea. Amenorrhea refers to more than three to six months without menses during a woman's reproductive years. The term for painful periods is dysmenorrhea.
There is a wide spectrum of differences in how women experience menstruation. There are several ways that someone's menstrual cycle can differ from the norm:

Term	Meaning
Oligomenorrhea	Infrequent periods
Hypomenorrhea	Short or light periods
Polymenorrhea	Frequent periods
Hypermenorrhea	Heavy or long periods
Dysmenorrhea	Painful periods
Intermenstrual bleeding	Breakthrough bleeding
Amenorrhea	Absent periods

Extreme psychological stress can also result in periods stopping. More severe symptoms of anxiety or depression may be signs of premenstrual dysphoric disorder which is a depressive disorder.
Dysfunctional uterine bleeding is a hormonally caused bleeding abnormality. Dysfunctional uterine bleeding typically occurs in premenopausal women who do not ovulate normally. All these bleeding abnormalities need medical attention; they may indicate hormone imbalances, uterine fibroids, or other problems. As pregnant women may bleed, a pregnancy test forms part of the evaluation of abnormal bleeding.
Women who had undergone female genital mutilation a practice common in parts of Africa, may experience menstrual problems, such as slow and painful menstruation, that is caused by the near-complete sealing off of the vagina.