Author: Dr Paula Hillard Stanford University 2008-08-11
Menstruation: Menstruation is the monthly vaginal bleeding that occurs in reproductive age women. The menstrual cycle refers to the monthly hormonal cycle that results in the shedding of the lining of the uterus, termed menstruation.
Menstruation: Menstruation is the monthly vaginal bleeding that occurs in reproductive age women. The menstrual cycle refers to the monthly hormonal cycle that results in the shedding of the lining of the uterus, termed menstruation.
GLOSSARY OF MENSTRUAL TERMS
These terms are commonly used by doctors and medical professionals, although many of the terms do not have precise definitions. To make matters more confusing, some of the terms may be either descriptive or may represent a diagnosis. There is currently a movement to do away with the more confusing terms, replacing them with terms that describe menstruation in terms of cycle regularity (irregular, regular, or absent); frequency (frequent, normal, or infrequent); duration of menstrual flow (prolonged, normal, or shortened); and volume of menstrual flow (heavy, normal, or light).
Abnormal Uterine Bleeding (AUB)—a term that has been proposed to describe any/all types of bleeding that do not fall within the normal ranges for amount, frequency, duration, or cyclicity
Amenorrhea— no menstrual bleeding for a variably-defined interval of time—often 6 months, but evidence suggests that no bleeding for more than 90 days is a better definition; Primary amenorrhea means no periods ever (by age 15), while secondary amenorrhea indicates no periods for 90 days at any point after periods have begun
Bleeding—In contraceptive clinical trials, a standard description of bleeding (as opposed to spotting) was defined by the World Health Organization as “vaginal blood loss requiring the use of sanitary protection such as pads or tampons” and termed the Belsey Criteria
Breakthrough Bleeding (BTB)—bleeding that occurs between expected menstrual periods; BTB is typically a description of unscheduled bleeding while women are using hormonal methods of contraception such as oral contraceptives
Dysfunctional Uterine Bleeding (DUB)—a frequently used, but poorly defined term. The most common definition of the term is bleeding that occurs after other specific causes of abnormal bleeding have been ruled out by history or laboratory studies. In practice, the term DUB is commonly used as a generic description of abnormal bleeding, and is often used prior to any testing that would more precisely characterize a cause of bleeding. This term sometimes refers to anovulatory bleeding.
Dysmenorrhea—menstrual cramps
Hypermenorrhea—excessively heavy menstrual bleeding, similar to either menorrhagia or metrorrhagia
Hypomenorrhea—excessively light menstrual bleeding
Intermenstrual bleeding—bleeding (usually lighter than typical) that occurs between cyclic menstrual periods
Menorrhagia—excessively heavy and/or prolonged menstrual bleeding, occurring at regular intervals
Menometrorrhagia—a term derived from combining the terms menorrhagia and metrorrhagia, implying heavy or prolonged bleeding, occurring irregularly
Metrorrhagia—Heavy and irregular bleeding
Menstruation—monthly bleeding in reproductive age women
Menstrual Period—an episode of menstrual bleeding, typically lasting 2-7 days
Menarche—the first menstrual period
Oligomenorrhea—Infrequent menstrual bleeding
Polymenorrhea—too frequent menstrual bleeding
Postcoital bleeding—bleeding occurring after intercourse
Postmenopausal bleeding—bleeding occurring after menopause (defined as one year of no bleeding)
Pubarche—the onset with puberty of pubic hair growth
Puberty—the process of sexual maturation and growth
Spotting—in contraceptive clinical trials, spotting has traditionally been defined by the WHO Belsey criteria (see bleeding) as “vaginal blood loss not necessitating sanitary protection”; a more recent (and more female-centered) definition has been suggested: "Bleeding that is contained or, in the woman's opinion, could have been contained by one sanitary pad or one tampon per 24-h time span, without soiling underclothes"
Thelarche—the onset with puberty of breast development
Unscheduled bleeding—bleeding that occurs during the use of hormonal contraceptives (such as oral contraceptive pills) at a time other than the expected (withdrawal) bleeding
Withdrawal bleeding—bleeding that occurs when hormone levels drop, such a bleeding that occurs at the end of each cycle of cyclic combined oral contraceptive pills; technically, this is different from a naturally occurring menstrual period because the hormonal events that cause it are different
MENSTRUATION
Menstruation
is the monthly vaginal bleeding that occurs in reproductive age women.
The menstrual cycle refers to the monthly hormonal cycle that results
in the shedding of the lining of the uterus (the endometrium), termed
menstruation (or menstrual bleeding, or menses, or a menstrual period).
Menarche, the first menstrual period, is the event that marks the
completion of a girl’s step-wise progression through puberty to sexual
maturity, when she is capable of becoming pregnant.
Puberty
Puberty
is the normal process of growth and development toward sexual
maturity. It is marked by a series of anatomic changes caused by
physiologic processes that typically occur in a step-wise fashion. In
girls, these changes are noticeable in breast growth as well as the
development of underarm (axillary) and pubic hair. Growth of the
internal genital organs (the ovaries, uterus, and vagina) also occurs,
but is not visible externally.
The processes that trigger puberty begin in middle childhood, with the secretion of the pituitary hormone Luteinizing Hormone (LH). Spikes of hormonal secretion occur during sleep, signaling the ovaries to begin to produce the female hormone, estrogen. Estrogen leads to breast growth and development. Estrogen also causes the lining of the uterus (the endometrium) to grow (proliferate).
In the past, doctors felt that any breast development beginning before age 8 was abnormal. More recent studies have suggested that pubertal development begins earlier, depending on a girl’s race or ethnic background. Normal breast development may begin as early as age 7 in African American girls, with an average age of around 8-9 years. In general, Mexican American girls begin puberty somewhat earlier than Caucasian girls, but later than African American girls. The average age for the beginning of breast development in Caucasian girls is about 10 years. Most girls start to develop breasts (called thelarche) before they start to develop pubic hair (termed pubarche), although African American girls are somewhat more likely than Caucasians to first develop pubic hair.
Growth of pubic hair is a result of the production of hormones from the adrenal gland, and occurs at about the same time as breast development, but is triggered in a different way. The development of underarm (axillary) body odor also results from this process. Breast development or the progression of puberty that occurs significantly earlier than age 7 may be due to serious medical conditions, and should be investigated. If breast development has not begun by age 13, there may be a medical cause that should be investigated.
A major growth spurt with growth in height begins soon after the beginning of breast growth. By the time a girl has progressed through puberty and had her first menstrual period, she will typically grow only a bit more than 2 inches in height.
Within about two years after the onset of breast development, the first period typically occurs. The medical term for the first menstrual period is menarche. With the menstrual period, the lining of the uterus (endometrium) is shed. The shedding of the surface layer of the endometrium is accompanied by bleeding. The average amount of menstrual blood lost with each menstrual period is about 35 ml (3 ½ Tablespoons), although this information is of little practical importance. The average age of menarche in the U.S. is between the ages of 12 and 13. African American girls experience a slightly earlier menarche on average than do Caucasian girls. If a girl has not had her period by age 15 (primary amenorrhea), she should see her doctor, as this is uncommon and may indicate a serious medical condition.
The processes that trigger puberty begin in middle childhood, with the secretion of the pituitary hormone Luteinizing Hormone (LH). Spikes of hormonal secretion occur during sleep, signaling the ovaries to begin to produce the female hormone, estrogen. Estrogen leads to breast growth and development. Estrogen also causes the lining of the uterus (the endometrium) to grow (proliferate).
In the past, doctors felt that any breast development beginning before age 8 was abnormal. More recent studies have suggested that pubertal development begins earlier, depending on a girl’s race or ethnic background. Normal breast development may begin as early as age 7 in African American girls, with an average age of around 8-9 years. In general, Mexican American girls begin puberty somewhat earlier than Caucasian girls, but later than African American girls. The average age for the beginning of breast development in Caucasian girls is about 10 years. Most girls start to develop breasts (called thelarche) before they start to develop pubic hair (termed pubarche), although African American girls are somewhat more likely than Caucasians to first develop pubic hair.
Growth of pubic hair is a result of the production of hormones from the adrenal gland, and occurs at about the same time as breast development, but is triggered in a different way. The development of underarm (axillary) body odor also results from this process. Breast development or the progression of puberty that occurs significantly earlier than age 7 may be due to serious medical conditions, and should be investigated. If breast development has not begun by age 13, there may be a medical cause that should be investigated.
A major growth spurt with growth in height begins soon after the beginning of breast growth. By the time a girl has progressed through puberty and had her first menstrual period, she will typically grow only a bit more than 2 inches in height.
Within about two years after the onset of breast development, the first period typically occurs. The medical term for the first menstrual period is menarche. With the menstrual period, the lining of the uterus (endometrium) is shed. The shedding of the surface layer of the endometrium is accompanied by bleeding. The average amount of menstrual blood lost with each menstrual period is about 35 ml (3 ½ Tablespoons), although this information is of little practical importance. The average age of menarche in the U.S. is between the ages of 12 and 13. African American girls experience a slightly earlier menarche on average than do Caucasian girls. If a girl has not had her period by age 15 (primary amenorrhea), she should see her doctor, as this is uncommon and may indicate a serious medical condition.
Physiology of Puberty—What’s happening in the body
A
menstrual period results from a coordinated feedback system in which
the female sexual organs, including the ovaries and uterus, interact
with the brain (pituitary and hypothalamus) via hormonal messengers. The
result of these interactions is that the superficial layer of the
endometrium is shed, if fertilization has not occurred. An idealized
menstrual cycle lasts approximately 28 days from the first day of
menstruation (defined as day 1 of the menstrual cycle). The term
menstrual cycle refers to the number of days from the beginning of one
period to the beginning of the next (NOT the end of one period to the
beginning of the next), and is different from the number of days of
menstrual flow or the menstrual period. See Know My Cycle for an animated view of the events occurring during the menstrual cycle that are described below.
The menstrual cycle has several different phases, as described below and in the link Endocrinology of the Menstrual Cycle [5].
The menstrual cycle includes the simultaneous and linked development
occurring within the ovary; the lining of the uterus (the endometrium);
and in the brain.
In the ovary, an egg (oocyte) matures within a cystic cavity called a follicle. The follicular phase of the menstrual cycles refers to the first half of the menstrual cycle, when the follicle is developing--see Follicular Development [3]. When the follicle has reached a certain size and stage of development, ovulation—the release of the egg—occurs. The egg then moves through the Fallopian tubes, where, if sperm are present, fertilization may occur. If fertilization does not occur, menstruation follows ovulation by about 14 days. After ovulation, the ovary secretes the hormone progesterone. Progesterone is secreted by a structure called the corpus luteum—which develops from the follicle after ovulation. The second phase of the menstrual cycle is thus sometimes called the luteal phase, when referring to ovarian function.
In the uterus, estrogen produces growth (proliferation) of the lining of the uterus, the endometrium. This part of the menstrual cycle is referred to as the proliferative phase when referring to events taking place within the uterus. The proliferative phase of endometrial growth corresponds to the follicular phase of ovarian growth. After ovulation, progesterone, produced by the ovary, causes changes in the glands of the endometrium. This phase of the menstrual cycle is called the secretory phase, so-named because the endometrial glands prepare to secrete substances that play a role in implantation of the developing embryo and in the development of the placenta, should a pregnancy occur. The secretory phase of endometrial development corresponds to the luteal phase of ovarian function. When a pregnancy does not occur, levels of progesterone drop, the lining of the uterus, which is rich in blood vessels, breaks down, and the superficial layer sloughs off. The menstrual flow consists of endometrial tissue, fluid, and blood, which are shed through the opening of the uterus, the cervix, into the vagina to exit the body at the opening of the vagina. see Endometrial Cycle (2)
In the brain, the portion of the brain called the hypothalamus produces gonadotropin releasing hormone (GnRH) which controls the release of two gonadotropins (hormones affecting the female gonads--the ovaries) Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) from the pituitary gland. See Introduction to hormones of the menstrual cycle [4]. The pituitary secretes low levels of FSH, which causes development of the follicle within the ovary. Ovulation is triggered by a spike in the production of LH, and to a lesser extent, FSH. The interaction between the hypothalamus, pituitary, and ovary (called the Hypothalamic-Pituitary-Ovarian axis or H-P-O) axis is complex, and involves both positive and negative feedback mechanisms, which result in a self-perpetuating monthly menstrual cycle. See Hormonal changes throughout the menstrual cycle to view an animation of these hormonal changes.[6] See the diagram of the H-P-O axis at Hypothalamic-Pituitary-Ovarian (HPO) axis [7]
In the ovary, an egg (oocyte) matures within a cystic cavity called a follicle. The follicular phase of the menstrual cycles refers to the first half of the menstrual cycle, when the follicle is developing--see Follicular Development [3]. When the follicle has reached a certain size and stage of development, ovulation—the release of the egg—occurs. The egg then moves through the Fallopian tubes, where, if sperm are present, fertilization may occur. If fertilization does not occur, menstruation follows ovulation by about 14 days. After ovulation, the ovary secretes the hormone progesterone. Progesterone is secreted by a structure called the corpus luteum—which develops from the follicle after ovulation. The second phase of the menstrual cycle is thus sometimes called the luteal phase, when referring to ovarian function.
In the uterus, estrogen produces growth (proliferation) of the lining of the uterus, the endometrium. This part of the menstrual cycle is referred to as the proliferative phase when referring to events taking place within the uterus. The proliferative phase of endometrial growth corresponds to the follicular phase of ovarian growth. After ovulation, progesterone, produced by the ovary, causes changes in the glands of the endometrium. This phase of the menstrual cycle is called the secretory phase, so-named because the endometrial glands prepare to secrete substances that play a role in implantation of the developing embryo and in the development of the placenta, should a pregnancy occur. The secretory phase of endometrial development corresponds to the luteal phase of ovarian function. When a pregnancy does not occur, levels of progesterone drop, the lining of the uterus, which is rich in blood vessels, breaks down, and the superficial layer sloughs off. The menstrual flow consists of endometrial tissue, fluid, and blood, which are shed through the opening of the uterus, the cervix, into the vagina to exit the body at the opening of the vagina. see Endometrial Cycle (2)
In the brain, the portion of the brain called the hypothalamus produces gonadotropin releasing hormone (GnRH) which controls the release of two gonadotropins (hormones affecting the female gonads--the ovaries) Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) from the pituitary gland. See Introduction to hormones of the menstrual cycle [4]. The pituitary secretes low levels of FSH, which causes development of the follicle within the ovary. Ovulation is triggered by a spike in the production of LH, and to a lesser extent, FSH. The interaction between the hypothalamus, pituitary, and ovary (called the Hypothalamic-Pituitary-Ovarian axis or H-P-O) axis is complex, and involves both positive and negative feedback mechanisms, which result in a self-perpetuating monthly menstrual cycle. See Hormonal changes throughout the menstrual cycle to view an animation of these hormonal changes.[6] See the diagram of the H-P-O axis at Hypothalamic-Pituitary-Ovarian (HPO) axis [7]
WHAT MAY BE ABNORMAL with Puberty
PUBERTY AND BREAST DEVELOPMENT
Information about the onset of pubertal development and what constitutes pubertal development that is too early (precocious puberty) are somewhat controversial. Some physicians still consider that any pubertal development prior to age 8 in girls should be evaluated by a physician, even though data suggest that this occurs in about 1 in 8 Caucasian girls, and nearly half of African-American girls. The majority of girls who begin to develop pubertal changes only slightly before age 8 will not have a serious medical cause, and early development is a variant of normal. However, conditions that are associated with precocious puberty include some very serious medical conditions, such as brain or ovarian tumors. After a medical evaluation, a medical cause is not found in the majority of cases of early pubertal development in girls (termed “idiopathic”). The younger the onset of precocious puberty, the more likely it is that there is a serious medical cause.
Pubertal development that begins TOO LATE with no breast development by age 13 may also be a variant of normal development—termed “constitutional delay.” However, this should not be assumed to be the case. Chromosomal problems, chronic diseases, excessive exercise, eating disorders, and other hormonal problems can cause pubertal delay. Here too, medical evaluation is appropriate.
MENARCHE
TOO EARLY onset of menstrual periods (prior to age 9) can result from the causes of precocious puberty. The onset of bleeding without pubertal development can be due to trauma (including sexual abuse), vulvar skin conditions (such as lichen sclerosus), or rare vaginal tumors. Vaginal bleeding in the absence of pubertal development ALWAYS deserves a medical assessment.
TOO LATE--The failure to experience menarche by age 14 ½ or 15 is statistically quite uncommon. While the textbooks say that primary amenorrhea is defined as the absence of a first period by age 16, most experts now believe that this guideline is too late. A number of medically important conditions with implications for long-term health can present with a delay in the onset of menarche. These conditions include problems with hormonal cycling such as Polycystic Ovarian Syndrome (PCOS), which is present in 5-7% of adult women, and which typically begins in adolescence; eating disorders such as anorexia nervosa or bulimia; other hormonal problems such as thyroid disease; chronic diseases such as diabetes or inflammatory bowel disease; anatomic birth defects including absence of the uterus or vagina or obstructing lesions such as an imperforate hymen; over exercise; or tumors of the ovary, adrenal, or pituitary gland. While stress may cause a delay in the onset of menstrual periods, it should not be assumed to be the cause without further medical testing. Some of these conditions can be life threatening (such as anorexia nervosa), while others are associated with the subsequent development of diabetes, early heart disease, or infertility (PCOS). In addition, a number of the causes of primary amenorrhea can be associated with a failure to attain an optimal bone mineral density, with possible increased risk of osteopenia/osteoporosis and bone fractures. Thus, the failure to have a menstrual period (achieve menarche)by age 15 should be taken seriously, and a medical evaluation is appropriate.
Information about the onset of pubertal development and what constitutes pubertal development that is too early (precocious puberty) are somewhat controversial. Some physicians still consider that any pubertal development prior to age 8 in girls should be evaluated by a physician, even though data suggest that this occurs in about 1 in 8 Caucasian girls, and nearly half of African-American girls. The majority of girls who begin to develop pubertal changes only slightly before age 8 will not have a serious medical cause, and early development is a variant of normal. However, conditions that are associated with precocious puberty include some very serious medical conditions, such as brain or ovarian tumors. After a medical evaluation, a medical cause is not found in the majority of cases of early pubertal development in girls (termed “idiopathic”). The younger the onset of precocious puberty, the more likely it is that there is a serious medical cause.
Pubertal development that begins TOO LATE with no breast development by age 13 may also be a variant of normal development—termed “constitutional delay.” However, this should not be assumed to be the case. Chromosomal problems, chronic diseases, excessive exercise, eating disorders, and other hormonal problems can cause pubertal delay. Here too, medical evaluation is appropriate.
MENARCHE
TOO EARLY onset of menstrual periods (prior to age 9) can result from the causes of precocious puberty. The onset of bleeding without pubertal development can be due to trauma (including sexual abuse), vulvar skin conditions (such as lichen sclerosus), or rare vaginal tumors. Vaginal bleeding in the absence of pubertal development ALWAYS deserves a medical assessment.
TOO LATE--The failure to experience menarche by age 14 ½ or 15 is statistically quite uncommon. While the textbooks say that primary amenorrhea is defined as the absence of a first period by age 16, most experts now believe that this guideline is too late. A number of medically important conditions with implications for long-term health can present with a delay in the onset of menarche. These conditions include problems with hormonal cycling such as Polycystic Ovarian Syndrome (PCOS), which is present in 5-7% of adult women, and which typically begins in adolescence; eating disorders such as anorexia nervosa or bulimia; other hormonal problems such as thyroid disease; chronic diseases such as diabetes or inflammatory bowel disease; anatomic birth defects including absence of the uterus or vagina or obstructing lesions such as an imperforate hymen; over exercise; or tumors of the ovary, adrenal, or pituitary gland. While stress may cause a delay in the onset of menstrual periods, it should not be assumed to be the cause without further medical testing. Some of these conditions can be life threatening (such as anorexia nervosa), while others are associated with the subsequent development of diabetes, early heart disease, or infertility (PCOS). In addition, a number of the causes of primary amenorrhea can be associated with a failure to attain an optimal bone mineral density, with possible increased risk of osteopenia/osteoporosis and bone fractures. Thus, the failure to have a menstrual period (achieve menarche)by age 15 should be taken seriously, and a medical evaluation is appropriate.
TABLE
QUICK GUIDE TO PERIODS: WHAT’S NORMAL/ WHAT’S NOT
PUBERTY
TYPICALLY pubertal development (breast growth and the appearance of pubic hair) in girls begins earlier than it does in boys.
TOO EARLY (termed Precocious Puberty)—before age 6 in African American girls or before age 7 in Caucasians
TOO LATE (Pubertal delay)—if there is no breast development by age 13
BREAST DEVELOPMENT
TYPICALLY around age 11
TOO EARLY—before age 6 in African American girls or before age 7 in Caucasians
TOO LATE—if no breast development by age 13
MENARCHE
TYPICALLY age 12-13; African American girls slightly earlier than Caucasians
TOO EARLY—before age 9
TOO LATE—No period by age 15 or by 2 ½-3 years after the onset of breast development
MENSTRUAL CYCLE LENGTH
ADOLESCENTS—20-45 days
ADULT WOMEN—21-34 days
No periods for >90 days (defined as amenorrhea) is abnormal in reproductive-age women, including teenagers
MENSTRUAL DURATION
TYPICAL—2-7 days
MENSTRUAL VOLUME
TYPICALLY—35 ml (the textbook answer—of no practical worth)
Average tampon/pad use -- each pad or tampon lasts 3-4 hours
TOO MUCH—85 ml or more per period leads to anemia if ongoing
Frequent tampon/pad use -- soaking one pad or tampon in 1-2 hours is a more useful or practical description. If this rate of bleeding last for longer than 2-4 hours, particularly if this is also associated with feeling light-headed or dizzy, medical advice should be sought.
QUICK GUIDE TO PERIODS: WHAT’S NORMAL/ WHAT’S NOT
PUBERTY
TYPICALLY pubertal development (breast growth and the appearance of pubic hair) in girls begins earlier than it does in boys.
TOO EARLY (termed Precocious Puberty)—before age 6 in African American girls or before age 7 in Caucasians
TOO LATE (Pubertal delay)—if there is no breast development by age 13
BREAST DEVELOPMENT
TYPICALLY around age 11
TOO EARLY—before age 6 in African American girls or before age 7 in Caucasians
TOO LATE—if no breast development by age 13
MENARCHE
TYPICALLY age 12-13; African American girls slightly earlier than Caucasians
TOO EARLY—before age 9
TOO LATE—No period by age 15 or by 2 ½-3 years after the onset of breast development
MENSTRUAL CYCLE LENGTH
ADOLESCENTS—20-45 days
ADULT WOMEN—21-34 days
No periods for >90 days (defined as amenorrhea) is abnormal in reproductive-age women, including teenagers
MENSTRUAL DURATION
TYPICAL—2-7 days
MENSTRUAL VOLUME
TYPICALLY—35 ml (the textbook answer—of no practical worth)
Average tampon/pad use -- each pad or tampon lasts 3-4 hours
TOO MUCH—85 ml or more per period leads to anemia if ongoing
Frequent tampon/pad use -- soaking one pad or tampon in 1-2 hours is a more useful or practical description. If this rate of bleeding last for longer than 2-4 hours, particularly if this is also associated with feeling light-headed or dizzy, medical advice should be sought.
MENSTRUAL CYCLE LENGTH, REGULARITY, and FREQUENCY
Menstrual
cycles during adolescence are more irregular than they are in older
reproductive-age women, but it is not true that “anything goes” with
menstrual cycles during the teenage years. The interval from the first
to the second menstrual period is the most variable, and in one study,
10% of girls had more than 60 days from the first period to the second.
It may take several years for cycles to be associated with regular
ovulation. Earlier menarche is associated with the earlier onset of
regular ovulatory cycles, while in girls who experience a later-onset
menarche, it may take 5-10 years for this to occur.
One
tool that can be very helpful in distinguishing normal menstrual
function from abnormal is the Menstrual Calendar. One example of a
menstrual calendar is seen here:
Instructions
with information about normal parameters for menstrual cycles in
adolescents are presented on the back of the card:
Regular bleeding
While some variability is to be expected in menstrual cycle length during adolescence, most cycles range from 21 to 45 days, even in the first gynecologic year (the first year after menarche). Typically, the trend is for increasing regularity and somewhat shorter cycles. By the third gynecologic year, 60-80% of girls are experiencing cycles that are ~24-38 days in length, as is typical in adult women.
Normal menstrual cycles in adult women typically fall between 24 and 38 days. See TABLE --"Normal" limits for Menstruation, based on several observational population studies. Cycles that are outside of this range or that have changed significantly from what a woman was previously experiencing may be caused by a variety of medical conditions, including conditions that are relatively benign or those that are medically serious, including cancer. Medical consultation with a gynecologist or other clinicians can help to determine a cause. See Table: Causes of Irregular Bleeding.
“The Menstrual Cycle is a Vital Sign”
During
what has been termed the middle reproductive years, extending from age
19 or so, until a woman’s early 40s, there is typically less variability
in a woman’s cycle length than there is during adolescence or during
the transition years leading up to menopause (defined as no bleeding for
one year). Menstrual regularity is a sign that generally can reflect
overall health and well-being.
It has been stated that “the menstrual cycle is a vital sign,” (R) suggesting that just as blood pressure, pulse, and respiration reflect health, so too does normal menstrual cyclicity. This phrase was chosen to reflect the fact that the absence of menstrual bleeding (unless hormonal treatment such as birth control pills or shot has been prescribed) suggests the possibility of underlying medical conditions or diseases that require further medical evaluation and testing. The absence of regular menstrual periods, or periods outside of the normal parameters suggested above should not be assumed to be due solely to “stress.” While stress may play a role, and stress may sometimes be found to be the primary reason for missed periods, other conditions should also be considered.
It has been stated that “the menstrual cycle is a vital sign,” (R) suggesting that just as blood pressure, pulse, and respiration reflect health, so too does normal menstrual cyclicity. This phrase was chosen to reflect the fact that the absence of menstrual bleeding (unless hormonal treatment such as birth control pills or shot has been prescribed) suggests the possibility of underlying medical conditions or diseases that require further medical evaluation and testing. The absence of regular menstrual periods, or periods outside of the normal parameters suggested above should not be assumed to be due solely to “stress.” While stress may play a role, and stress may sometimes be found to be the primary reason for missed periods, other conditions should also be considered.
Typically,
menstrual bleeding lasts 2-7 days, with most women experiencing 4-5
days of flow. While most women recognize that prolonged bleeding is a
problem, many women do not recognize that bleeding that lasts longer
than a week is uncommon, and likely due to a specific cause that should
be determined. Bleeding that lasts less than 2 days is also uncommon,
but it may not be recognized as abnormal, in that many women are not
unhappy to have shorter periods.
Medical textbooks rely on
studies that measure the volume of blood loss with a period to determine
what is normal. These studies indicate that the average blood loss per
menstrual period is about 35 ml. While this figure is widely cited, it
does not entirely explain perceptions of bleeding, which can vary
depending on age, past experiences, and family descriptions of typical
bleeding. In addition, menstrual fluid volume makes up a significant
component of menstrual flow, and is not always measured in studies of
blood loss. These studies themselves are not easy to do. Of course the
figure of 35 ml as average is practically quite useless for individual
women.
ABNORMAL BLEEDING
Infrequent or absent bleeding
Cycles longer than 90 days are abnormal in any age reproductive woman, and can be defined as amenorrhea. Some older medical textbooks suggest that a definition of amenorrhea is no periods for 6 months, or for an interval of longer than 3 of the previously experienced cycles. However, statistically, ninety days represents the 95th percentile for cycle length, even during adolescence, and thus is a more evidence-based definition for amenorrhea. Adolescents or adult women who are not taking any hormonal medication (such as birth control pills) who go for more than 90 days without a period should be evaluated by a clinician, rather than reassured that this can be “normal for teenagers” or “due to stress.” When a woman has previously had menstrual cycles, the absence of bleeding for 90 days or more is termed secondary amenorrhea.
The most common cause of missed periods in all women is pregnancy. In the U.S. about half of all pregnancies are unintended (See Pie Chart); women who are sexually active who are not using any method of birth control account for about half of those unintended pregnancies, but the other half occur in women who are using a method of birth control. All methods of contraception can fail, but some methods are more reliable at preventing pregnancy than others (World Health Organization Contraceptive Effectiveness ).
Cycles longer than 90 days are abnormal in any age reproductive woman, and can be defined as amenorrhea. Some older medical textbooks suggest that a definition of amenorrhea is no periods for 6 months, or for an interval of longer than 3 of the previously experienced cycles. However, statistically, ninety days represents the 95th percentile for cycle length, even during adolescence, and thus is a more evidence-based definition for amenorrhea. Adolescents or adult women who are not taking any hormonal medication (such as birth control pills) who go for more than 90 days without a period should be evaluated by a clinician, rather than reassured that this can be “normal for teenagers” or “due to stress.” When a woman has previously had menstrual cycles, the absence of bleeding for 90 days or more is termed secondary amenorrhea.
The most common cause of missed periods in all women is pregnancy. In the U.S. about half of all pregnancies are unintended (See Pie Chart); women who are sexually active who are not using any method of birth control account for about half of those unintended pregnancies, but the other half occur in women who are using a method of birth control. All methods of contraception can fail, but some methods are more reliable at preventing pregnancy than others (World Health Organization Contraceptive Effectiveness ).
[13]
Anovulation: Failure or disruption of the complex feedback mechanisms of the H-P-O axis can result in a failure to ovulate, termed anovulation. This is one of the most common causes of abnormal bleeding. Menstrual bleeding associated with anovulation can be prolonged, heavy, too frequent, or too infrequent. The term Dysfunctional Uterine Bleeding (DUB) is often used to describe anovulatory bleeding after other causes of bleeding have been ruled out by history or laboratory testing, although this term is imprecise, and may be used differently in the U.S. than in other countries.
For many years, physicians have used terms to describe the menstrual cycle that might facetiously be described as “Medicalese”. A list of these terms and their definitions is presented in the glossary. While seemingly precise, many of these terms do not truly have specific and universally accepted definitions. More recently, there has been an international move toward standardizing the terminology, describing abnormal bleeding more consistently and simply in terms of regularity, frequency, duration, and amount of flow.
CYCLE: NORMAL
Regularity Irregular Regular Absent
Frequency of Menstruation Frequent Normal Infrequent
Duration of Menstrual Flow Prolonged Normal Shortened
Volume of Menstrual Flow Heavy Normal Light
Regularity Irregular Regular Absent
Frequency of Menstruation Frequent Normal Infrequent
Duration of Menstrual Flow Prolonged Normal Shortened
Volume of Menstrual Flow Heavy Normal Light
Parameters
for normal menstrual characteristics for women in their middle
reproductive years are included in TABLE "Normal" Limits for
Menstruation, which is based on evidence from a number of studies.
Ovarian Insufficiency/Premature Ovarian Failure (POF)
Ovarian insufficiency is a term that describes waning ovarian hormonal function. This decline in ovarian function typically takes place over several years, and may wax and wane. As a result, menstrual cycles and periods become irregular. Ultimately, this may result in a cessation of normal cyclic hormonal cycles. When this occurs prior to age 40, the term Premature Ovarian Failure (POF) or less correctly, “premature menopause” has been used. Relative ovarian insufficiency results in irregular bleeding and variable menstrual cycles, similar to that which is seen with a natural menopause. As with a natural menopause which signals the end of childbearing potential, ovarian insufficiency is typically associated with infertility, although spontaneous ovulations can occur during the interval of cycle variability. There are many causes of ovarian insufficiency, but some cases are thought to have an autoimmune mechanism. In most cases, the specific cause is not known--the medical term for this is Primary Ovarian Insufficiency. A number of health problems, including low bone density are associated with Primary Ovarian Insufficiency.Because POF can occur even during early adolescence, the cause of amenorrhea and irregular menstrual periods should be investigated before moving forward with therapy, such as birth control pills “to regulate the cycle.” While birth control pills (oral contraceptives) or other hormonal contraceptives such as the transdermal patch or vaginal ring can accomplish cycle regulation, and they are generally safe for most women, failure to diagnose a serious underlying medical condition such as POF can have significant consequences for future health and fertility.
Irregular Bleeding
See TABLE--Common Causes of Menstrual Irregularity
The
causes of cycles that are extended/too long (>38 days in adult women
or >45 days in adolescence) are similar to those listed for menarche
that occurs TOO LATE, with the exception of anatomic abnormalities
which are typically diagnosed during adolescence. The most common cause
of irregular bleeding (both too frequent and too infrequent) aside from
pregnancy-related problems such as a threatened miscarriage or
incomplete miscarriage (medical term threatened or incomplete
spontaneous abortion) is anovulation (see above).
Frequent Bleeding
Bleeding that happens more frequently than every 21 days can be due to anovulation (which itself can have a number of different causes). While Abnormal Uterine Bleeding (AUB) is a term that is often used to describe any bleeding without regard to specific cause, not all of the causes of bleeding from the vagina are caused by problems of the uterus; cervical, vaginal, and vulvar conditions can also cause abnormal bleeding. The distinction also needs to be made between abnormal bleeding that occurs spontaneously in the absence of a hormonal medication (such as birth control pills) and irregular or unscheduled bleeding or breakthrough bleeding that occurs while an individual is taking hormones. The specific causes of abnormal bleeding occurring during hormonal therapy are very different (and typically less worrisome) than the causes of abnormal bleeding occurring IN THE ABSENCE OF prescribed hormones.
Abnormally Heavy Menstrual Flow Duration And Volume
Menstrual bleeding typically lasts from 2 to 7 days, with most women experiencing 4-5 days of flow. Bleeding that is prolonged can result from a variety of conditions. Menorrhagia is an older term used to describe regular, but prolonged or heavy periods. The term is not precise, and should be discarded (see table 2) in favor of simply describing the bleeding as prolonged in duration. Prolonged bleeding can result from anovulation, pregnancy-related causes such as miscarriage, anatomic causes such as uterine fibroids, and disorders of blood clotting (coagulation problems or coagulopathies).
Approximately 1% of the general population has a coagulation problem called von Willebrand disease, which is familial, and which may be very mild or severe and life threatening. It is a type of hemophilia. In one study, women who came to an emergency department with acute (sudden onset) or heavy or prolonged bleeding (termed hemorrhage) were tested to determine the cause. About one half of those who were experiencing their very first menstrual period (menarche) had disorders of blood clotting; the percentage of women with a clotting disorders was lower among women presenting with hemorrhage who were not experiencing their first period, but overall, studies suggest that as many as 20% of all women with severely heavy periods may have a blood disorder. Because the condition is familial, there may be several generations of women who have had menstrual problems (“Everyone in my family has heavy periods, and both my mother and grandmother had a hysterectomy when they were young”) and heavy or prolonged bleeding may be perceived to be the norm.
Medical textbooks rely on studies that measure the volume of blood loss with a period to determine what is normal. These studies indicate that the average blood loss is about 35 ml. Monthly bleeding greater than 80 ml is likely to lead to anemia, and thus heavy bleeding is defined as greater than 80 ml. These studies are not easy to do, and the results are not practically useful. Because most women do not have a benchmark against which to compare their menstrual bleeding, other than their own experiences, some women who meet the criteria of bleeding greater than 80 ml/month describe their periods as “normal,” while other women whose blood loss falls within the normal range, describe their periods as “heavy.” Practically, many physicians define heavy bleeding as bleeding that soaks one pad or tampon in 1-2 hours. If this rate of bleeding lasts for longer than 2-4 hours, particularly if this is also associated with feeling light-headed or dizzy, medical advice should be sought. When medical testing is done to determine the cause of heavy menstrual bleeding, a complete blood count (CBC) will determine if anemia is present. Tests of blood clotting function may also be indicated, although conditions such as von Willebrand disease can be difficult to diagnose.
Frequent Bleeding
Bleeding that happens more frequently than every 21 days can be due to anovulation (which itself can have a number of different causes). While Abnormal Uterine Bleeding (AUB) is a term that is often used to describe any bleeding without regard to specific cause, not all of the causes of bleeding from the vagina are caused by problems of the uterus; cervical, vaginal, and vulvar conditions can also cause abnormal bleeding. The distinction also needs to be made between abnormal bleeding that occurs spontaneously in the absence of a hormonal medication (such as birth control pills) and irregular or unscheduled bleeding or breakthrough bleeding that occurs while an individual is taking hormones. The specific causes of abnormal bleeding occurring during hormonal therapy are very different (and typically less worrisome) than the causes of abnormal bleeding occurring IN THE ABSENCE OF prescribed hormones.
Abnormally Heavy Menstrual Flow Duration And Volume
Menstrual bleeding typically lasts from 2 to 7 days, with most women experiencing 4-5 days of flow. Bleeding that is prolonged can result from a variety of conditions. Menorrhagia is an older term used to describe regular, but prolonged or heavy periods. The term is not precise, and should be discarded (see table 2) in favor of simply describing the bleeding as prolonged in duration. Prolonged bleeding can result from anovulation, pregnancy-related causes such as miscarriage, anatomic causes such as uterine fibroids, and disorders of blood clotting (coagulation problems or coagulopathies).
Approximately 1% of the general population has a coagulation problem called von Willebrand disease, which is familial, and which may be very mild or severe and life threatening. It is a type of hemophilia. In one study, women who came to an emergency department with acute (sudden onset) or heavy or prolonged bleeding (termed hemorrhage) were tested to determine the cause. About one half of those who were experiencing their very first menstrual period (menarche) had disorders of blood clotting; the percentage of women with a clotting disorders was lower among women presenting with hemorrhage who were not experiencing their first period, but overall, studies suggest that as many as 20% of all women with severely heavy periods may have a blood disorder. Because the condition is familial, there may be several generations of women who have had menstrual problems (“Everyone in my family has heavy periods, and both my mother and grandmother had a hysterectomy when they were young”) and heavy or prolonged bleeding may be perceived to be the norm.
Medical textbooks rely on studies that measure the volume of blood loss with a period to determine what is normal. These studies indicate that the average blood loss is about 35 ml. Monthly bleeding greater than 80 ml is likely to lead to anemia, and thus heavy bleeding is defined as greater than 80 ml. These studies are not easy to do, and the results are not practically useful. Because most women do not have a benchmark against which to compare their menstrual bleeding, other than their own experiences, some women who meet the criteria of bleeding greater than 80 ml/month describe their periods as “normal,” while other women whose blood loss falls within the normal range, describe their periods as “heavy.” Practically, many physicians define heavy bleeding as bleeding that soaks one pad or tampon in 1-2 hours. If this rate of bleeding lasts for longer than 2-4 hours, particularly if this is also associated with feeling light-headed or dizzy, medical advice should be sought. When medical testing is done to determine the cause of heavy menstrual bleeding, a complete blood count (CBC) will determine if anemia is present. Tests of blood clotting function may also be indicated, although conditions such as von Willebrand disease can be difficult to diagnose.
MENSTRUAL PAIN/ DYSMENORRHEA
The medical term for painful menstruation is dysmenorrhea. It is typically a lower abdominal, crampy, midline pain. Primary dysmenorrhea begins during adolescence, and is typically not associated with significant structural or anatomic problems. Secondary dysmenorrhea typically begins late in life, and is due to the presence of gynecologic/pelvic disease, such as endometriosis or uterine fibroids (leiomyoma). Most teens experience dysmenorrhea, which occurs in 60-93% of adolescents. About 15% of adolescents describe severe menstrual symptoms. Primary dysmenorrhea typically begins within a day of the onset of menstrual bleeding; it is most intense for the first 1-2 days of flow. The crampy pain may radiate to the back or thighs and may be accompanied by other menstrual or premenstrual molimina. Menstrual (or premenstrual) molimina refers to the other uncomfortable symptoms around the time of menses, such as breast tenderness, abdominal bloating, mood changes, headaches, nausea, and exacerbation of symptoms such as diarrhea associated with irritable bowel syndrome. Dysmenorrhea and menstrual molimina are associated with ovulatory cycles. Primary dysmenorrhea results from elevated production of prostaglandins and other mediators in the uterus that produce constriction of uterine blood vessels, which leaders to lack of blood flow (vasoconstriction) and contractions of the uterine muscle.
Secondary dysmenorrhea is distinguished from primary dysmenorrhea by virtue of its onset may begin 1-2 weeks before the onset of bleeding, and often lasts throughout the days of menstrual flow.
CAUSES of SECONDARY DYSMENORRHEA include:
EndometriosisUterine tumors, most commonly uterine fibroids (leiomyoma)
Pelvic scar tissue (adhesions)
Adenomyosis
Cervical narrowing (stenosis)
Pelvic infection
Uterine/endometrial polyps
Non-medicated IUDs
Cervical cancer
Uterine or ovarian tumors
Endometrial polyp
Treatment for Dysmenorrhea
Because the causes of dysmenorrhea include an excess production of substances known as prostaglandins, medications that suppress the action or production of prostaglandins are often quite effective in providing relief. These medications are termed non-steroidal anti-inflammatory drugs (NSAIDs). Several different NSAIDs, including ibuprofen and naproxen, are available without a prescription (Over-the-counter or OTC), and are typically much more effective for dysmenorrhea than other types of simple pain medications (analgesics) such as acetaminophen (Tylenol®) or the very mild anti-prostaglandin effects of aspirin. Several combination products are widely marketed in the U.S. for management of menstrual symptoms. Different combinations of acetaminophen, pamabrom, pyrilamine, caffeine, and in some formulations ibuprofen or naproxen are present in the various formulations; the buyer is encouraged to choose a product containing one of the NSAIDS, and to be aware that little data exist to support the benefits of the other components.
Ibuprofen and naproxen are two NSAIDS that are available over-the-counter. Nonsteroidal anti-inflammatory drugs have been shown in randomized controls to be significantly more effective for pain relief than placebo for dysmenorrhea. These over-the-counter drugs have the same active ingredient as similar prescription medications, but differ in the dose contained in each pill and in their guidelines for frequency of dosing. There are a number of potential side effects of these medications, and they should be used cautiously in women with certain medical conditions (such as asthma or a history of stomach/duodenal ulcers). They should be taken with food to avoid causing serious gastrointestinal bleeding. In treating dysmenorrhea, NSAIDS should be taken prior to the onset of severe cramps, as they work in part by blocking the production of prostaglandins. A slightly higher dose may be taken initially (called a loading dose) to assure adequate blood levels of the drug. In addition, they may be more effective if taken on a “scheduled” basis for 1-2 days; this means that the dose of medication is scheduled (every 6 hours with ibuprofen or every 12 hours with naproxen) rather than taken on a pain-contingent basis. This also helps to assure consistent blood levels, which provides improved pain relief. One to two days of NSAIDs taken in this fashion is often sufficient to allow normal activities for girls and women with primary dysmenorrhea.
Oral contraceptives have been widely used to manage menstrual pain and symptoms, and many clinicians observe that they can be very effective for some women. There is some evidence of their benefit over placebo therapy in randomized controlled trials, although some of these studies involved the use of medium doses of estrogen that are higher than those commonly prescribed today.
Recently, extended cycle oral contraceptives have been marketed. One formulation contains 84 days of hormonally active pills followed by 7 days of placebo; another is similar with 84 hormonally active pills, but contains 7 estrogen tablets in place of placebo; and a 365 daily hormonal formulation pill has also been approved and marketed. Combination oral contraceptive (COC) pills containing both estrogen and a synthetic form of progestin are effective for contraception because they suppress ovulation; prostaglandin production is also reduced with COCs. One potential benefit of extended oral contraceptive regimens is that fewer menstrual periods often mean less frequent menstrual symptoms such as menstrual cramps. The potential for this benefit must be balanced with a greater risk of unscheduled bleeding, particularly in early months of use.
Another option that has been shown in randomized controlled clinical trials to be effective for the treatment of menstrual cramps and pain include high frequency transcutaneous electrical nerve stimulation (TENS). Some benefit and promise has been shown for other alternative treatments, including acupuncture, Chinese herbal medicine, Vitamin B1, Vitamin B6, Vitamin E, magnesium, omega-3 fatty acids (fish oil), and topical heat. There is some evidence from randomized clinical trials that behavioral interventions, including relaxation and pain management techniques may be effective for managing dysmenorrhea. Systematic review yields insufficient evidence to recommend the use of surgical procedures involving the use of nerve interruption in the management of dysmenorrhea. There is no evidence to suggest that spinal manipulation (chiropracty) is effective in the treatment of dysmenorrhea.
Premenstrual Syndrome
(PMS) refers to symptoms (emotional and behavioral as well as physical
symptoms) that are consistently and only present in the days before the
period begins, that resolve shortly after menstrual bleeding begins, and
that interfere with normal activities. While the majority of women
experience at least one premenstrual symptom, most do not have
premenstrual symptoms that interfere with activities. Premenstrual
Dysphoric Disorder (PMDD) is a more severe type of PMS that has strictly
defined diagnostic criteria. Dysmenorrhea is NOT typically considered a
symptom of PMS or PMDD.
Menopause
The medical definition of menopause is the absence of menstrual bleeding for an interval of one year. Obviously, the final menstrual period (FMP) is something that must be determined retrospectively, and thus the medical definition is not as useful prospectively. Many women think about menopause as an interval of time prior to and including the final menstrual period, and extending some variable interval of time after menstrual bleeding stops. Clinicians may refer to the “perimenopause” or the menopausal transition to encompass this understanding of the interval leading up to the final menstrual period and extending 1 year beyond that event. Menopausal symptoms (hot flashes, vaginal dryness) may begin during the perimenopause, and may last for 6 years or more. See menopause information for consumers from the North American Menopause Society (NAMS).Menstrual patterns during the menopausal transition tend to become more variable, with variations in cycle length/frequency of bleeding, as well as the duration and amount of flow. One study that followed women over several years around the time of menopause found that nearly all those who reported that they 1) had experienced an interval of 90 days without bleeding, 2) had “skipped a period” in the last year, 3) had variation in cycle lengths by 19 or more days, 4) experienced variation in cycle length such that they could not predict a usual length, and 5) reported cycles to be less regular than they had been at age 40 went on to experience menopause within 4 years. Two-thirds of women reporting these symptoms experienced menopause within 2 years. For many women approaching menopause, cycles shorten by 3-7 days as the result of a shortened ovarian follicular phase. Cycles may become more irregular; there may be intervals of no bleeding or long cycles followed by short cycles. For some women, these intervals of irregularity are followed by return to regular monthly bleeding, although the length of this return to normal cyclicity is variable.
While these changes in menstrual bleeding can be bothersome or worrisome for the woman who is experiencing them, the variability is not of itself a sign of medical disease. Tracking the dates of menstrual bleeding prospectively on a menstrual calendar can be compared with the general norms noted in TABLE 3. In general, bleeding outside of those normal parameters requires an assessment so that causes of bleeding that are medically serious – such as endometrial hyperplasia (which can be pre-cancerous) or endometrial cancer – are excluded. In particular, bleeding occurring more frequently than every 24 days merits an evaluation for women in their 40s. This evaluation may include a transvaginal pelvic ultrasound, saline infusion sonohysterography, and sampling of the tissue lining the uterus (an endometrial biopsy). Sometimes further evaluation is needed with a D&C (Dilation and Curettage) and hysteroscopy.
TABLE "Normal" limits for Menstruation
From Fraser IS et al[8]
Based on data from Treloar et al[9]; Hallberg et al[10]; Snowden and Christian, eds[11];, Belsey and Pinol[12]
TABLE: COMMON CAUSES OF MENSTRUAL IRREGULARITY/ABNORMAL UTERINE BLEEDING
Pregnancy
Menopause
Endocrine causes:
Polycystic Ovarian Syndrome (PCOS)
Thyroid disease
Ovarian insufficiency (traditionally called Premature Ovarian Failure –POF)
Acquired Conditions:
Stress-related hypothalamic dysfunction
Medications
Chronic diseases
Exercise-induced
Eating disorders (anorexia nervosa and bulimia)
Bleeding due to hormone medications (contraceptives)
LESS COMMON, BUT IMPORTANT CAUSES
Tumors:
Ovarian
Adrenal
Pituitary
Late-onset congenital adrenal hyperplasia
Table: Causes of Menstrual Irregularity/Abnormal Uterine Bleeding--Extensive List
For MORE Information:
See the American College of Obstetricians and Gynecologists (ACOG) for Patient Education Pamphlets including:
Menstruation—Especially for Teens
Growing Up—Especially for Teens
Dysmenorrhea
Uterine Fibroids
Abnormal Uterine Bleeding
Menopausal Bleeding
Polycystic Ovary Syndrome
Midlife Transitions: A Guide to Approaching Menopause
The Menopause Years
and Others
See The North American Menopause Society (NAMS) with consumer information
See
the Museum of Menstruation (MOM) web site—Quirky, reasonably well
researched, full of real comments from real people; oddly organized;
VERY long list of words and expressions for menstruation at Museum of Menstruation
Fact Sheets
Menstruation and the Menstrual Cycle from womenshealth.gov
Articles in the Scientific and Medical Literature:
1. Fraser, I.S., et al., Can we achieve international agreement on terminologies and definitions used to describe abnormalities of menstrual bleeding? Hum Reprod, 2007. 22(3): p. 635-43.
2. Adams Hillard, P.J., Menstruation in young girls: a clinical perspective. Obstetrics & Gynecology, 2002. 99(4): p. 655-62.
3. Treloar, A.E., et al., Variation of the human menstrual cycle through reproductive life. Int J Fertil, 1967. 12: p. 77-126.
4. ACOG Committee Opinion No. 349, November 2006: Menstruation in girls and adolescents: using the menstrual cycle as a vital sign. Obstet Gynecol, 2006. 108(5): p. 1323-8.
5. Lukes, A.S., et al., Disorders of hemostasis and excessive menstrual bleeding: prevalence and clinical impact. Fertility and sterility, 2005. 84(5): p. 1338-1344.
6. Marjoribanks, J., M.L. Proctor, and C. Farquhar, Nonsteroidal anti-inflammatory drugs for primary dysmenorrhoea. Cochrane Database Syst Rev, 2003. 2(4): p. CD002751.
7. Fraser, I.S., P. Warner, and P.A. Marantos, Estimating menstrual blood loss in women with normal and excessive menstrual fluid volume. Obstet Gynecol, 2001. 98(5 Pt 1): p. 806-14.
Menstruation and the Menstrual Cycle from womenshealth.gov
Articles in the Scientific and Medical Literature:
1. Fraser, I.S., et al., Can we achieve international agreement on terminologies and definitions used to describe abnormalities of menstrual bleeding? Hum Reprod, 2007. 22(3): p. 635-43.
2. Adams Hillard, P.J., Menstruation in young girls: a clinical perspective. Obstetrics & Gynecology, 2002. 99(4): p. 655-62.
3. Treloar, A.E., et al., Variation of the human menstrual cycle through reproductive life. Int J Fertil, 1967. 12: p. 77-126.
4. ACOG Committee Opinion No. 349, November 2006: Menstruation in girls and adolescents: using the menstrual cycle as a vital sign. Obstet Gynecol, 2006. 108(5): p. 1323-8.
5. Lukes, A.S., et al., Disorders of hemostasis and excessive menstrual bleeding: prevalence and clinical impact. Fertility and sterility, 2005. 84(5): p. 1338-1344.
6. Marjoribanks, J., M.L. Proctor, and C. Farquhar, Nonsteroidal anti-inflammatory drugs for primary dysmenorrhoea. Cochrane Database Syst Rev, 2003. 2(4): p. CD002751.
7. Fraser, I.S., P. Warner, and P.A. Marantos, Estimating menstrual blood loss in women with normal and excessive menstrual fluid volume. Obstet Gynecol, 2001. 98(5 Pt 1): p. 806-14.
References
- McGill Molson Medical Informatics Student Projects Site
http://sprojects.mmi.mcgill.ca/menstrual cycle/physiology.htm l - La
Barbera, A., K. Sliney, and K. Marsh. The Endometrial Cycle.
Reproductive Physiology. University of Cincinnati College of Medicine
[Animation] 2007 01/01/2007 [cited 2008 03/30/2008]; Available from:
http://http://www.healcentral.org/healap p/showMetadata?metad ataId=38389 - McGill Molson Medical Infomatics Student Projects Site
http://sprojects.mmi.mcgill.ca/menstrual cycle/folliculardeve lopmentpage.html - McGill Molson Medical Infomatics Students Projects Site
http://sprojects.mmi.mcgill.ca/menstrual cycle/endocrinology. html - McGill Molson Medical Infomatics Students Projects Site
http://sprojects.mmi.mcgill.ca/menstrual cycle/physiology.htm l - La
Barbera, A., K. Marsh, and K. Sliney. Hormonal Changes Throughout the
Menstrual Cycle. Reproductive Physiology. University of Cincinnati
College of Medicine [Animation] 2007 01/01/2007 [cited 2008 03/30/2008];
http://www.healcentral.org/healapp/showM etadata?metadataId=3 8641#rights - McGill Molson Medical Infomatics Students Projects Site
http://sprojects.mmi.mcgill.ca/menstrual cycle/hypothalamicpi tuitaryaxis.html - Fraser IS et al. A process designed to lead to international agreement on terminologies of menstrual bleeding. Fertil and Steril 2007; 87:466-76
- Treloar, A.E., et al., Variation of the human menstrual cycle through reproductive life. Int J Fertil, 1967. 12: p. 77-126.
- Hallberg, L., et al., Menstrual blood loss--a population study. Variation at different ages and attempts to define normality. Acta Obstet Gynecol Scand, 1966. 45(3): p. 320-51.
- Snowden, R. and B. Christian, eds. Patterns and Perception s of Menstruation (A World Health Organization International study). 1983, Croom Helm: London. p. 339.
- Belsey, E.M. and A.P. Pinol, Menstrual bleeding patterns in untreated women. Task Force on Long-Acting Systemic Agents for Fertility Regulation. Contraception, 1997. 55(2): p. 57-65.
- Finer, L.B. and S.K. Henshaw, Disparities in rates of unintended pregnancy in the United States, 1994 and 2001. Perspect Sex Reprod Health, 2006. 38(2): p. 90-6.