The first menstrual period, usually occurring during puberty.
[MEN(O)– + Greek arkhē, beginning (from arkhein, to begin).]
menarcheal me·nar'che·al adj.
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The first menstrual period, usually occurring during puberty.
[MEN(O)– + Greek arkhē, beginning (from arkhein, to begin).]
menarcheal me·nar'che·al adj.The first menstruation which occurs at puberty. The majority of girls (95%) reach menarche between 11 and 15 years of age, the average being about 13 years. Ovulation can occur at the time of menarche but usually this does not happen for several months or even up to 2 years later. Thus the first few menstrual cycles are often anovulatory and hence infertile.
— S. A. W.
See menstrual cycle.
The initiation of menstruation in adolescent girls, normally occurring between the ages of 11 and 15. The age at menarche has become younger in Western countries, possibly associated with a better general standard of nutrition, and is later in less-developed countries.
The onset of menstruation defined by the first appearance of menstrual flow. The age of menarche varies from country to country, but in the USA and UK it generally begins at about 12 to 13 years of age. The age of menarch has come down on average over the last two generations, with diets being generally more adequate during childhood. However, girls who exercise strenuously, particularly female athletes with long, lithe bodies, may have their menarche delayed until their late teens. It is not clear whether this has long-term beneficial or harmful effects, but generally the later the menarche the higher the incidence of subsequent menstrual irregularities. See also amenorrhoea.
The beginning of the menstrual function.
The onset of menstruation defined by the appearance of the first menstrual flow. Regular high-intensity exercise may delay menarche in female athletes with long, lithe bodies. It is not clear what long-term effect that this delay has. See also amenorrhoea.
Menarche (IPA: /məˈnɑrki/) is the
first menstrual period, or first menstrual bleeding in the females of human beings. From both social and medical perspectives it is often considered the central event of female
puberty, as it signals the possibility of
Menarche is the culmination of a series of physiological and anatomic processes of puberty, described in more detail in that article:
A specific hormonal signal for menarche is not known; menarche as a discrete event is thought to be the relatively chance result of the gradual thickening of the endometrium induced by rising but fluctuating pubertal estrogen.
The menstruum, or "flow", consists of a combination of fresh and clotted blood with endometrial tissue. The initial flow of menarche is usually brighter red than mature menstrual flow. It is often scanty in amount and may be very brief, even a single instance of "spotting". Like other menses, menarche may be accompanied by abdominal cramping.
In most girls, menarche does not signal that ovulation has occurred. Studies of American girls suggest that the average interval between menarche and ovulation is several months. Irregular, anovulatory menses commonly occur for 1-2 years or more before regular ovulation is established.
Regular ovulation is usually indicated by predictable and consistent intervals between menses, predictable and consistent durations of menses, and predictable and consistent patterns of flow (e.g., heaviness or cramping). Continuing ovulation typically requires a body fat content of at least 22%. An anthropological term for this state of potential fertility is nubility.
On the other hand, not every girl follows the typical pattern and some girls have ovulated before the first menstruation. Although unlikely, it is possible for a girl engaging in sexual intercourse shortly before her menarche would occur to conceive and become pregnant, delaying her menarche until after the birth. This would be a rare exception to the widely held assumption that a woman cannot become pregnant until after menarche.
Some of the least understood environmental influences on timing of puberty are social and psychological. Nearly all of the research on these effects has concerned girls, partly because female puberty requires greater physiologic resources and partly because it involves a unique event (menarche) that makes survey research into female puberty much simpler than male. In most of these studies menarche was specifically examined, assuming it to be a valid "proxy" for the more general process of puberty. In comparison with the effects of genetics, nutrition, and general health, social influences are small, shifting timing by a few months rather than years. The most important part of a child's psychosocial environment is the family.
Some of the aspects of family structure and function reported to be independently associated with earlier menarche:
Some of the aspects of family structure and function reported to be independently associated with later menarche:
Other research has focused on the effect of childhood stress on timing of puberty, especially female. Stress is a vague term and studies have examined conditions ranging from family tensions or conflict to wartime refugee status with threat to physical survival. The more dire social conditions have been found to be associated with delay of maturation, an effect that may be compounded by dietary inadequacy. There is more uncertainty and mixed evidence as to whether milder degrees of stress or early-life undernutrition can accelerate puberty in girls as would be predicted by life history theory and demonstrated in many other mammals.
The understanding of these environmental effects is incomplete and the following observations and cautions are relevant:
There were few systematic studies of timing of menarche before the latter half of the 20th century. Most older estimates of average timing of menarche were based on observation of a small homogeneous population not necessarily representative of the larger population, or based on recall by adult women, which is also susceptible to various forms of error. Most sources agree that average age of menarche in girls in modern societies has declined, though the reasons and the degree remain subjects of controversy. There have been claims of a 2 to 2.5 year decline from about 1900 to the 1960s, but the best North American surveys reported only a 2-3 month decline from the mid-1970s to the mid-1990s. This is commonly attributed to larger body size and earlier average attainment of sufficient body fat, but other factors such as environmental exposure to chemicals that mimic estrogen or the urbanization or "sexualization" of Western society have also been offered by some.
Less than 10% of US girls start to menstruate before 11 years of age, and 90% of all US girls are menstruating by 13.75 years of age, with a median age of 12.43 years. This age at menarche is not significantly different (0.34 years earlier) than that reported for US girls in 1973. Age at menarche for non-Hispanic black girls was significantly earlier than that of white girls at 10%, 25%, and 50% of those who had attained menarche, whereas Mexican American girls were only significantly earlier than the white girls at 25%. [1]
Menarche is celebrated in many cultures around the world as a rite of passage, a time to recognize that a girl is moving into womanhood.
Some cultures have in past centuries have had rites of passage for a girl experiencing menarche.
When menarche occurs, it confirms that the girl has had a gradual estrogen-induced growth of the uterus, especially the endometrium, and that the "outflow tract" from the uterus, through the cervix to the vagina, is open.
In very rare instances, menarche may occur at an unusually early age, preceding thelarche and other signs of puberty. This is termed isolated premature menarche, but other causes of bleeding must be investigated and excluded. Growth is usually normal. [2] Isolated premature menarche is rarely the first manifestation of precocious puberty.
When menarche has failed to occur for more than 3 years after thelarche, or past 16 years of age, the delay is referred to as primary amenorrhea.
| Physiology, endocrinology, sex: Reproductive physiology and endocrinology | |
|---|---|
| Menstrual cycle/Estrous cycle | Menstruation - Follicular phase - Ovulation - Luteal phase |
| Gametogenesis | Spermatogenesis -Oogenesis |
| Sexuality | Human sexual
behavior - Sexual intercourse - Erection -
Ejaculation - Orgasm - Insemination - Fertilisation/ |
| Lifespan | Prenatal development - Sexual dimorphism - Sexual differentiation - Puberty (Menarche, Adrenarche) - Maternal age/Paternal age - Climacteric (Menopause, Andropause) |
| Eggs | Oviposition - Oviparity - Ovoviviparity - Viviparity |
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