What is the average menstruation cycle length?
Menstrual synchrony
Strassmann argued menstrual synchrony defined as menstruation overlap should be quite common. For example, the expected difference by chance between two women with 28-day cycles—which is approximately the average length of menstrual cycles of women at the age —is 7 days. Considering that the mean duration of menses is 5 days and the range is 2 to 7 days, the probability of menstruation overlap by chance should be high.
Menstrual disorder
Abnormal uterine bleeding is a general category that includes any bleeding from menstrual or nonmenstrual causes. Hypomenorrhea is abnormally light menstrual periods. Menorrhagia (meno = month, rrhagia = excessive flow/discharge) is an abnormally heavy and prolonged menstrual period. Metrorrhagia is bleeding at irregular times, especially outside the expected intervals of the menstrual cycle. If there is excessive menstrual and uterine bleeding other than that caused by menstruation, menometrorrhagia (meno = prolonged, metro = uterine, rrhagia = excessive flow/discharge) may be diagnosed. Causes may be due to abnormal blood clotting, disruption of normal hormonal regulation of periods or disorders of the endometrial lining of the uterus. Depending upon the cause, it may be associated with abnormally painful periods.
Menstrual cycle
The degree of ovulation suppression in progestogen-only contraceptives depends on the progestogen activity and dose. Low dose progestogen-only contraceptives—traditional progestogen only pills, subdermal implants Norplant and Jadelle, and intrauterine system Mirena—inhibit ovulation in about 50% of cycles and rely mainly on other effects, such as thickening of cervical mucus, for their contraceptive effectiveness. Intermediate dose progestogen-only contraceptives—the progestogen-only pill Cerazette and the subdermal implant Nexplanon—allow some follicular development but more consistently inhibit ovulation in 97–99% of cycles. The same cervical mucus changes occur as with very low-dose progestogens. High-dose, progestogen-only contraceptives—the injectables Depo-Provera and Noristerat—completely inhibit follicular development and ovulation.
Edward R. Dewey
Volume IV of the Cycles Classic Library Collection contains 1380 reports of cycles period determinations by scientists, doctors, economists and cycles researchers. In these reports there is a tendency for certain periods of cycles to be reported more commonly. These common periods include the underlined periods above and some other periods such as 9.6 years, found in the 9.6 year cycle of lynx abundance and 3.39 years (40.68 months), found in the US stock market, which Dewey says is the most commonly found period. Dewey further said that:
Anovulation
Anovulation is usually associated with specific symptoms. However, it is important to note that they are not necessarily all displayed simultaneously. Amenorrhea (absence of menstruation) occurs in about 20% of women with ovulatory dysfunction. Infrequent and light menstruation occurs in about 40% of women with ovulatory dysfunction. Another potential symptom is irregular menstruation, where five or more menstrual cycles a year are five or more days shorter or longer than the length of the average cycle. Absence of mastodynia (breast pain or tenderness) occurs in about 20% of women with ovulatory problems. Also possible is increased body mass and facial hair, which is relatively easy to treat, and is often associated with PCOS, or polycystic ovary syndrome.
Menstrual cycle
As measured on women undergoing in vitro fertilization, a longer menstrual cycle length is associated with higher pregnancy and delivery rates, even after age adjustment. Delivery rates after IVF have been estimated to be almost doubled for women with a menstrual cycle length of more than 34 days compared with women with a menstrual cycle length shorter than 26 days. A longer menstrual cycle length is also significantly associated with better ovarian response to gonadotropin stimulation and embryo quality.
Nyala
Before ovulation, the Graafian follicles reach a length of at least . A female's estrus cycle is about 19 days long. Males mate with the female for two days of the cycle, but she allows it for only six hours per cycle. When the male enters a females' herd during mating, he makes a display by raising his white dorsal crest, lowering his horns and moving stiffly. As in many other animals, the males fight over dominance during mating.
Menstrual cycle
"Eumenorrhea" denotes normal, regular menstruation that lasts for a few days (usually 3 to 5 days, but anywhere from 2 to 7 days is considered normal). The average blood loss during menstruation is 35 milliliters with 10–80 ml considered normal. Women who experience Menorrhagia are more susceptible to iron deficiency than the average person. An enzyme called plasmin inhibits clotting in the menstrual fluid.
Common torpedo
The common torpedo is aplacental viviparous, in which the embryos are sustained by yolk, supplemented by histotroph ("uterine milk") secreted by the mother. However, the organic content of the histotroph in this species is only 1.2%, much lower than in stingrays, and the embryo loses mass over the course of development as its initial yolk supply is expended for metabolic processes. Adult females have two functional ovaries and two functional uteruses, though the reproductive tract on the right side is more developed and consequently tends to carry more embryos. It has an annual reproductive cycle with well-defined seasonality, though the details differ between geographic regions. In the Mediterranean, mating occurs from December to February and birthing from late August to early September after a gestation period of 4–6 months; litter sizes range up to 19 and the newborns measure long. By contrast, off West Africa the gestation period lasts 6–8 months and birthing occurs from September to October; litter sizes range up to 28 and the newborns measure long. The litter size increases with female size.
Menstrual cycle
Females have been found to experience different eating habits at different stages of their menstrual cycle, with food intake being higher during the luteal phase than the follicular phase. Food intake increases by approximately 10% during the luteal phase compared to the follicular phase.
Menstrual cycle
Painful cramping in the abdomen, back, or upper thighs is common during the first few days of menstruation. Severe uterine pain during menstruation is known as dysmenorrhea, and it is most common among adolescents and younger women (affecting about 67.2% of adolescent females). When menstruation begins, symptoms of premenstrual syndrome (PMS) such as breast tenderness and irritability generally decrease. Many sanitary products are marketed to women for use during their menstruation.
Endometrium
In humans, the cycle of building and shedding the endometrial lining lasts an average of 28 days. The endometrium develops at different rates in different mammals. Various factors including the seasons, climate, and stress can affect its development. The endometrium itself produces certain hormones at different stages of the cycle and this affects other parts of the reproductive system.
Puberty
The first menstrual bleeding is referred to as menarche, and typically occurs about two years after thelarche. The average age of menarche is 12.5 in the United States. Most American girls experience their first period at 11, 12 or 13, but some experience it earlier than their 11th birthday and others after their 14th birthday. In fact, anytime between 8 and 16 is normal. In Canada, the average age of menarche is 12.72, and in the United Kingdom it is 12.9. The time between menstrual periods (menses) is not always regular in the first two years after menarche. Ovulation is necessary for fertility, but may or may not accompany the earliest menses. In postmenarchal girls, about 80% of the cycles were anovulatory in the first year after menarche, 50% in the third year and 10% in the sixth year. Initiation of ovulation after menarche is not inevitable. A high proportion of girls with continued irregularity in the menstrual cycle several years from menarche will continue to have prolonged irregularity and anovulation, and are at higher risk for reduced fertility.
Natural Cycles
The most recent published clinical study showed that natural cycles, when used correctly, is as effective in preventing pregnancies as the contraceptive pill.
The study analysed 22,785 women through a total of 224,563 menstrual cycles across a year, to calculate the app’s Pearl Index – the rate used to measure a contraceptive effectiveness. It found that if used perfectly – using protection such as condoms on red days – effectiveness is 99 percent. Typical use, where people become pregnant for all possible reasons, leads to 93 percent effectiveness. This is well above other Fertility awareness based methods that rate at around 75 percent and even the contraceptive pill, which rates at 91 percent. Further studies include the “Identification and prediction of the fertile window using Natural Cycles" and “Fertility awareness-based mobile application for contraception”. For the app to remain effective, women need to follow the app's instructions correctly, and it does not protect its users from sexually transmitted diseases.
Menstrual cycle
The different phases of the menstrual cycle correlate with women's moods. In some cases, hormones released during the menstrual cycle can cause behavioral changes in females; mild to severe mood changes can occur. The menstrual cycle phase and ovarian hormones may contribute to increased empathy in women. The natural shift of hormone levels during the different phases of the menstrual cycle has been studied in conjunction with test scores. When completing empathy exercises, women in the follicular stage of their menstrual cycle performed better than women in their midluteal phase. A significant correlation between progesterone levels and the ability to accurately recognize emotion was found. Performances on emotion recognition tasks were better when women had lower progesterone levels. Women in the follicular stage showed higher emotion recognition accuracy than their midluteal phase counterparts. Women were found to react more to negative stimuli when in midluteal stage over the women in the follicular stage, perhaps indicating more reactivity to social stress during that menstrual cycle phase. Overall, it has been found that women in the follicular phase demonstrated better performance in tasks that contain empathetic traits.
Bombus morio
Not much is known about the colony cycle of the "Bombus morio." There have been some hints about the length of their cycles, however. The longevity of individual workers within a eusocial bee species is one of the most important indicators of colony growth and reproductive rates of bee colonies. In the "Bombus morio," the average worker bee lives about 41.3 days. Additionally, the egg-to-adult period is about 32 days for workers, 35 days formales, and 32 for queens. These lengths are longer than the average and indicate slow colony growth.
Menstrual cycle
The average age of menarche is 12–15. They may occasionally start as early as eight, and this onset may still be normal. This first period often occurs later in the developing world than the developed world.
Fertility awareness
Most menstrual cycles have several days at the beginning that are infertile (pre-ovulatory infertility), a period of fertility, and then several days just before the next menstruation that are infertile (post-ovulatory infertility). The first day of red bleeding is considered day one of the menstrual cycle. Different systems of fertility awareness calculate the fertile period in slightly different ways, using primary fertility signs, cycle history, or both.
Functional hypothalamic amenorrhea
Females who have menstrual cycles lasting longer than 45 days and/or amenorrhea for three or more months should be evaluated for FHA. Differentiating FHA from the irregular menstrual patterns seen in adolescents during the initial years after menarche due to immaturity of the HPO axis can be challenging. However, studies have shown that even during this period, the length of a menstrual cycle does not exceed 45 days. Furthermore, healthy girls with normal BMI (18.5-25 kg/m) should develop regular menstrual cycles (every 28 +/- 3-5 days) within 1-2 years after menarche. FHA is a diagnosis of exclusion, and thus the evaluation should be used to rule out organic causes of amenorrhea (e.g., pregnancy, thyroid disorders, inflammatory bowel disease, etc.) Evaluation for FHA may include a thorough history and physical exam, laboratory testing, and imaging if appropriate. The Endocrine Society Clinical Practice Guidelines on Functional Hypothalamic Amenorrhea (FHA) suggests obtaining a baseline bone mineral density measurement by DEXA scan from any patient with 6 or more months of amenorrhea.
Menstruation
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, any of which should be discussed with a doctor to identify the underlying cause:
There is a movement among gynecologists to discard the terms noted above, which although they are widely used, do not have precise definitions. Many now argue to describe menstruation in simple terminology, including:
Menstrual cycle
In a number of countries, mainly in Asia, legislation or corporate practice has introduced formal menstrual leave to provide women with either paid or unpaid leave of absence from their employment while they are menstruating. Countries with policies include Japan, Taiwan, Indonesia, and South Korea. The practice is controversial due to concerns that it bolsters the perception of women as weak, inefficient workers, as well as concerns that it is unfair to men.
Menstrual cycle
Sexual feelings and behaviors change during the menstrual cycle. Before and during ovulation, high levels of estrogen and androgens result in women having an increased interest in sexual activity. Unlike other animal species, women show interest in sex across all days of the menstrual cycle, regardless of fertility.
Menstruation
Perimenopause is when fertility in a female declines, and menstruation occurs less regularly in the years leading up to the final menstrual period, when a female 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 in Western countries.
Gestational age
The mean pregnancy length has been estimated to be 283.4 days of gestational age as timed from the first day of the last menstrual period and 280.6 days when retrospectively estimated by obstetric ultrasound measurement of the fetal biparietal diameter (BPD) in the second trimester. Other algorithms take into account other variables, such as whether this is the first or subsequent child, the mother's race, age, length of menstrual cycle, and menstrual regularity. In order to have a standard reference point, the normal pregnancy duration is assumed by medical professionals to be 280 days (or 40 weeks) of gestational age. Furthermore, actual childbirth has only a certain probability of occurring within the limits of the estimated due date. A study of singleton live births came to the result that childbirth has a standard deviation of 14 days when gestational age is estimated by first trimester ultrasound, and 16 days when estimated directly by last menstrual period.
Menstrual cycle
Preferences for voice pitch change across the cycle. When seeking a short term mating partner, women may prefer a male with a low voice pitch, particularly during the fertile phase. During the late follicular phase, it is common for women demonstrate a preference for mates with a masculine, deep voice. Research has also been conducted on the attractiveness of the female voice throughout the cycle. During their most fertile phase of the menstrual cycle, there is some evidence that female voices are rated as significantly more attractive. This effect is not found with women on the birth control pill.
Menopause
The term "perimenopause", which literally means "around the menopause", refers to the menopause transition years before the date of the final episode of flow. According to the North American Menopause Society, this transition can last for four to eight years. The Centre for Menstrual Cycle and Ovulation Research describes it as a six- to ten-year phase ending 12 months after the last menstrual period.
Basal body temperature
Regular menstrual cycles are often taken as evidence that a woman is ovulating normally, and irregular cycles is evidence she is not. However, many women with irregular cycles do ovulate normally, and some with regular cycles are actually anovulatory or have a luteal phase defect. Records of basal body temperature can be used to accurately determine if a woman is ovulating, and if the length of the post-ovulatory (luteal) phase of her menstrual cycle is long enough to sustain a pregnancy.
Miscarriage
Some health organizations recommend that sexual activity be delayed after the miscarriage. The menstrual cycle should resume after about three to four months. Women report that they were dissatisfied with the care they received from physicians and nurses.
Menstrual cycle
Women's preference for male's body odor can change across the menstrual cycle. Males who score highly on dominance have been rated as sexier by females during the fertile phase of the menstrual cycle. Additionally, during their most fertile phase of the menstrual cycle, women may show preference for the odor of symmetrical men. This effect is not found for women on the birth control pill. Also, during the late follicular and ovulatory phases, women prefer the scent of masculine men. The scent of androsterone (responsible for testosterone levels) is highly preferred by women during the peak of their fertility in the menstrual cycle. Moreover, women may demonstrate preference for men with a scent that indicates developmental stability.
Addax
In a study, the blood serum of female addax was analyzed through immunoassay to know about their luteal phase. Estrous cycle duration was of about 33 days. During pregnancy, ultrasonography showed the uterine horns as coiled. The maximum diameters of the ovarian follicle and the corpus luteum were and . Each female underwent an anovulatory period lasting 39 to 131 days, during which there was no ovulation. Anovulation was rare in winter, which suggested the effect of seasons on the estrous cycle.
Pregnancy
Pregnancy is typically broken into three periods, or trimesters, each of about three months. Each trimester is defined as 14 weeks, for a total duration of 42 weeks, although the average duration of pregnancy is 40 weeks.
House dust mite
The average life cycle for a house dust mite is 65–100 days. A mated female house dust mite can last up to 70 days, laying 60 to 100 eggs in the last five weeks of her life. In a 10-week life span, a house dust mite will produce approximately 2,000 fecal particles and an even larger number of partially digested enzyme-covered dust particles.
Menarche
In most girls, menarche does not mean that ovulation has occurred. In postmenarchal girls, about 80% of the cycles were anovulatory in the first year after menarche, 50% in the third and 10% in the sixth year. 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.
Anovulation
The standard dosage for first-time takers is 50 or 100 mg of clomifene per day for five consecutive days, starting early in the menstrual cycle, usually on the third to fifth day counting from the beginning of the menstrual period. In case of amenorrhea, a period can be induced by intake of an oral progestin for 10 days. In absence of success, the dosage can be increased in subsequent cycles with increments of 50 mg. However, at a dosage of 200 mg, further increments are unlikely to increase pregnancy chances.
Ovulation
In humans, ovulation occurs about midway through the menstrual cycle, after the follicular phase. The few days surrounding ovulation (from approximately days 10 to 18 of a 28-day cycle), constitute the most fertile phase. The time from the beginning of the last menstrual period (LMP) until ovulation is, on average, 14.6 days, but with substantial variation between females and between cycles in any single female, with an overall 95% prediction interval of 8.2 to 20.5 days.
Human sexuality
Ovulation is based on a monthly cycle; the 14th day is the most fertile. On days one to four, menstruation and production of estrogen and progesterone decreases, and the endometrium starts thinning. The endometrium is sloughed off for the next three to six days. Once menstruation ends, the cycle begins again with an FSH surge from the pituitary gland. Days five to thirteen are known as the pre-ovulatory stage. During this stage, the pituitary gland secretes follicle-stimulating hormone (FSH). A negative feedback loop is enacted when estrogen is secreted to inhibit the release of FSH. Estrogen thickens the endometrium of the uterus. A surge of Luteinizing Hormone (LH) triggers ovulation. On day 14, the LH surge causes a Graafian follicle to surface the ovary. The follicle ruptures and the ripe ovum is expelled into the abdominal cavity. The fallopian tubes pick up the ovum with the fimbria. The cervical mucus changes to aid the movement of sperm. On days 15 to 28—the post-ovulatory stage, the Graafian follicle—now called the corpus luteum—secretes estrogen. Production of progesterone increases, inhibiting LH release. The endometrium thickens to prepare for implantation, and the ovum travels down the Fallopian tubes to the uterus. If the ovum is not fertilized and does not implant, menstruation begins.
Menopause
The menopause transition typically begins between 40 and 50 years of age (average 47.5). The duration of perimenopause may be for up to eight years. Women will often, but not always, start these transitions (perimenopause and menopause) about the same time as their mother did.
Age and female fertility
The average age of a young woman's first period (menarche) is 12 to 13 (12.5 years in the United States, 12.72 in Canada, 12.9 in the UK) but, in postmenarchal girls, about 80% of the cycles are anovulatory in the first year after menarche, 50% in the third and 10% in the sixth year. A woman's fertility peaks in her early and mid-20s after which it starts to decline. However, the exact estimates of the chances of a woman to conceive after a certain age are not clear, and are subject to debate.
Lunar month
Regardless of the culture, all lunar months approximate the mean length of the synodic month, the average period the Moon takes to cycle through its phases (new, first quarter, full, last quarter) and back again: 29–30 days. The Moon completes one orbit around Earth every 27.3 days (a sidereal month), but due to Earth's orbital motion around the Sun, the Moon does not yet finish a synodic cycle until it has reached the point in its orbit where the Sun is in the same relative position.
Menstrual cycle
Preferences for body features can change during the fertile phase of the cycle. Women seeking a short-term partner demonstrate a preference for taller and muscular males. Women also show preferences of males with masculine bodies at peak fertility. Mixed research has been found regarding body symmetry preferences throughout different phases of the cycle.
Metonic cycle
Meton of Athens approximated the cycle to a whole number (6,940) of days, obtained by 125 long months of 30 days and 110 short months of 29 days. During the next century, Callippus developed the Callippic cycle of four 19-year periods for a 76-year cycle with a mean year of exactly 365.25 days.
Menstrual disorder
"Polymenorrhea" is the medical term for cycles with intervals of 21 days or fewer.
Menopause
Menopause, also known as the climacteric, is the time in most women's lives when menstrual periods stop permanently, and they are no longer able to bear children. Menopause typically occurs between 49 and 52 years of age. Medical professionals often define menopause as having occurred when a woman has not had any vaginal bleeding for a year. It may also be defined by a decrease in hormone production by the ovaries. In those who have had surgery to remove their uterus but still have ovaries, menopause may be viewed to have occurred at the time of the surgery or when their hormone levels fell. Following the removal of the uterus, symptoms typically occur earlier, at an average of 45 years of age.
In the years before menopause, a woman's periods typically become irregular, which means that periods may be longer or shorter in duration or be lighter or heavier in the amount of flow. During this time, women often experience hot flashes; these typically last from 30 seconds to ten minutes and may be associated with shivering, sweating, and reddening of the skin. Hot flashes often stop occurring after a year or two. Other symptoms may include vaginal dryness, trouble sleeping, and mood changes. The severity of symptoms varies between women. While menopause is often thought to be linked to an increase in heart disease, this primarily occurs due to increasing age and does not have a direct relationship with menopause. In some women, problems that were present like endometriosis or painful periods will improve after menopause.
Menopause is usually a natural change. It can occur earlier in those who smoke tobacco. Other causes include surgery that removes both ovaries or some types of chemotherapy. At the physiological level, menopause happens because of a decrease in the ovaries' production of the hormones estrogen and progesterone. While typically not needed, a diagnosis of menopause can be confirmed by measuring hormone levels in the blood or urine. Menopause is the opposite of menarche, the time when a girl's periods start.
Specific treatment is not usually needed. Some symptoms, however, may be improved with treatment. With respect to hot flashes, avoiding smoking, caffeine, and alcohol is often recommended. Sleeping in a cool room and using a fan may help. The following medications may help: menopausal hormone therapy (MHT), clonidine, gabapentin, or selective serotonin reuptake inhibitors. Exercise may help with sleeping problems. While MHT was once routinely prescribed, it is now only recommended in those with significant symptoms, as there are concerns about side effects. High-quality evidence for the effectiveness of alternative medicine has not been found. There is tentative evidence for phytoestrogens.
Mare
The estrous cycle, also known as "season" or "heat" of a mare occurs roughly every 19–22 days and occurs from early spring into autumn. As the days shorten, most mares enter an "anestrus" period during the winter and thus do not cycle in this period. The reproductive cycle in a mare is controlled by the photoperiod (length of the day), the cycle first triggered when the days begin to lengthen. As the days shorten, the mare returns to the anestrus period when she is not sexually receptive. Anestrus prevents the mare from conceiving in the winter months, as that would result in her foaling during the harshest part of the year, a time when it would be most difficult for the foal to survive.
Dog behavior
Female dogs have an estrous cycle that is nonseasonal and monestrus, i.e. there is only one estrus per estrous cycle. The interval between one estrus and another is, on average, seven months, however, this may range between 4 and 12 months. This interestrous period is not influenced by the photoperiod or pregnancy. The average duration of estrus is 9 days with spontaneous ovulation usually about 3 days after the onset of estrus.
Culture and menstruation
To many, such cultural associations appear persuasive in view of the fact that in humans, the menstrual cycle quite closely approximates the moon's 29.5-day synodic cycle, unlike in chimpanzees (~36 days) or bonobos (~40 days). Statistical information from hunter gatherers is lacking, but where large-scale western studies focus on women's peak reproductive years—removing outlier values—the cycle length gravitates around 29.1–29.5 days, while the figure for women in their thirties shortens toward 28 days. In no extant human population has statistically significant lunar phase-locking been demonstrated.
Pharmacokinetics of progesterone
The biological half-life of progesterone in the circulation is very short; with intravenous injection, its half-life has ranged widely from 3 to 90 minutes in various studies. The metabolic clearance rate of progesterone ranges between 2,100 and 2,800 L/day, and is constant across the menstrual cycle.
Progesterone is eliminated in bile and urine.
Centre for Menstrual Cycle and Ovulation Research
CeMCOR published over 50 scientific papers in its first 10 years, as well as 4 books. Areas of research include menstruation and ovulation, bone health, premenopausal breast cancer, polycystic ovary syndrome (PCOS), and perimenopause. CeMCOR has stated that its research shows overall that regular menstrual cycles with ovulation help prevent osteoporosis, breast cancer, and heart disease. Dr. Prior has called menstrual cycles "a vital sign".
CeMCOR does not conduct research funded by the pharmaceutical industry.
Fertility awareness
Calendar rules may set a standard number of days, specifying that (depending on a woman's past cycle lengths) the first three to six days of each menstrual cycle are considered infertile. Or, a calendar rule may require calculation, for example holding that the length of the pre-ovulatory infertile phase is equal to the length of a woman's shortest cycle minus 21 days. Rather than being tied to cycle length, a calendar rule may be determined from the cycle day on which a woman observes a thermal shift. One system has the length of the pre-ovulatory infertile phase equal to a woman's earliest historical day of temperature rise minus seven days.
Extended cycle combined hormonal contraceptive
Before the advent of modern contraceptives, reproductive age women spent most of their time either pregnant or nursing. In modern western society women typically have about 450 periods during their lives, as compared to about 160 formerly.
Menstrual cycle
A number of factors affect whether dieting will affect these menstrual processes: age, weight loss and the diet itself. First, younger women are likely to experience menstrual irregularities due to their diet. Second, menstrual abnormalities are more likely with more weight loss. For example, anovulatory cycles can occur as a result of adopting a restricted diet, as well as engaging in a high amount of exercise. Finally, the cycle is affected more by a vegetarian diet compared to a non-vegetarian diet.
Menstrual cup
While numerous companies all over the world offer this product it was still not well known in around 2010. It may be difficult for companies to make profit from this product as one single menstrual cup can last a girl or woman five years or longer. Most women hear of menstrual cups through the internet or word of mouth, rather than through conventional advertizing on TV for example. As of 2018, menstrual cups are mentioned more and more often alongside tampons and pads in publications about menstrual hygiene management.
Lunar effect
It is widely believed that the Moon has a relationship with fertility due to the corresponding human menstrual cycle, which averages 28 days. However, no connection between lunar rhythms and menstrual onset has been conclusively shown to exist, and the similarity in length between the two cycles is most likely coincidental.
Menstrual disorder
"Irregular menstruation" is where there is variation in menstrual cycle length of more than approximately eight days for a woman. The term "metrorrhagia" is often used for irregular menstruation that occurs between the expected menstrual periods.
Menstrual cycle
Even though the average length of the human menstrual cycle is similar to that of the lunar cycle, in modern humans there is no relation between the two. The relationship is believed to be a coincidence. Light exposure does not appear to affect the menstrual cycle in humans. A meta-analysis of studies from 1996 showed no correlation between the human menstrual cycle and the lunar cycle, nor did data analysed by period-tracking app Clue, submitted by 1.5m women, of 7.5m menstrual cycles.
Tropical year
The Gregorian calendar, as used for civil and scientific purposes, is an international standard. It is a solar calendar that is designed to maintain synchrony with the mean tropical year . It has a cycle of 400 years (146,097 days). Each cycle repeats the months, dates, and weekdays. The average year length is 146,097/400 = = 365.2425 days per year, a close approximation to the mean tropical year .
Human reproductive ecology
The regular menstrual cycle is associated with the hormonal regulation from hypothalamic, pituitary, and ovarian axis. Gonadotropin-releasing hormone (GnRH) secretes from the hypothalamus. Hypothalamic GnRH pulse influences the pulsatile secretion of Follicle stimulating hormone (FSH) and Luteinizing hormone (LH) from the pituitary gland. During the menstrual cycle, due to a decreased level of inhibin-A and steroid hormones, the level of FSH increases. Due to these hormonal changes, the corpus luteum gets destroyed. The elevated level of FSH helps to recruit a cohort of the FSH-sensitive antral follicles in that cycle. During this phase, elevated FSH level stimulates the production of estradiol, Inhibin A and B. Following that, due to the negative feedback mechanism the level of estradiol and Inhibin-B increases and FSH level declines and it helps to select the dominant follicle. During the menopausal transition, FSH level elevates at the early follicular phase and due to the increased FSH level, the number of FSH-sensitive follicles decreases. These series of events lead to irregular menstrual cycle and the cycle length starts to become shorter. FSH, Inhibin-B, and Anti-Mullerian hormone (AMH) are used as the biomarkers for the ovarian aging.
Sexual attraction
Research has also found that menstrual cycles affect sexual behaviour frequency in pre-menopausal women. For example, women who had weekly sexual intercourse with men had menstrual cycles with the average duration of 29 days, while women with less frequent sexual interactions tended to have more extreme cycle lengths.
Quintaglio Ascension Trilogy
The estrous cycle of female Quintaglios is 18 thousand days, and a female will hopefully mate 4 times in her lifetime every cycle, normally. There are some exceptions though, as Natova, and one of her daughter with Afsan, arose when 16 thousand days old. Also some females will often at the estrous cycle, thus having very low fertility. While male can mate at almost anytime, they have to wait for a chance, when a female is currently about to enter the cycle and accept the invitation. Females do not have to stick with one male every time, instead, they follow their instinct and choose the right spouse for the moment. Despite living on their own territory, the Quintaglios often have a long lasting friendship with the previous spouses, with the possibility of some forms of pair bonding.
Chandravakyas
The Moon's orbit approximates an ellipse rather than a circle. The orientation and the shape of this orbit is not fixed. In particular, the positions of the extreme points,
the point of closest approach (perigee) and the point of farthest excursion (apogee), make a full circle in about nine years. It takes the Moon longer to return to the same position, perigee or apogee, because it moved ahead during one revolution. This longer period is called the anomalistic month, and has an average length of 27.554551 days (27 d 13 h 18 min 33.2 s). The apparent diameter of the Moon varies with this period. 9 anomalistic months constitute a period of approximately 248 days. The differences in the longitudes of the Moon on the successive days of a 248-day cycle constitute the "Chandravākyas". Each set of "Chandravākyas" contains a list of 248 "Vākyās" or sentences.
Tide
The approximately fortnightly tidal cycle has large effects on intertidal and marine organisms. Hence their biological rhythms tend to occur in rough multiples of this period. Many other animals such as the vertebrates, display similar rhythms. Examples include gestation and egg hatching. In humans, the menstrual cycle lasts roughly a lunar month, an even multiple of the tidal period. Such parallels at least hint at the common descent of all animals from a marine ancestor.
Menstrual synchrony
In addition to the study they conducted with lesbian couples, Weller and Weller conducted a number of other studies on menstrual synchrony during the 1990s. In most studies they reported finding menstrual synchrony, but in some studies they did not find synchrony. In a methodological review article in 1997, they refined their approach to measuring to better handle the problem of cycle variability. Specifically, they concluded that several menstrual cycles should be measured from each woman and that the longest average cycle length in a pair or group of women should be the basis for calculating the expected cycle onset difference. Thus, their research falls into the pre-1997 methodology and post-1997 methodology.
Extended cycle combined hormonal contraceptive
With all extended-cycle COCPs, breakthrough bleeding is the most common side effect, although it tends to decrease over time. In a 12-month study of a continuous COCP regimen, 59% of women experienced no bleeding in months six through twelve and 79% of women experienced no bleeding in month twelve. Extended or continuous use of COCPs or other combined hormonal contraceptives carries the same risk of side effects and medical risks as traditional COCP use. 
One of the early extended-cycle COCPs, Seasonale, was marketed with the campaign, ""Fewer periods. More possibilities."" In December 2004, Barr Pharmaceuticals was warned by the FDA concerning these television advertisements. As the warning stated, ""By omitting and minimizing the risks associated with Seasonale, the TV ad misleadingly suggests that Seasonale is safer than has been demonstrated by substantial evidence or substantial clinical experience."" Although clinical studies had proven Seasonale to be effective in preventing pregnancy, the FDA felt the commercial advertisements omitted the common side effects of irregular vaginal bleeding or spotting.
Bonobo
Bonobo reproductive rates are no higher than those of the common chimpanzee. During oestrus, females undergo a swelling of the perineal tissue lasting 10 to 20 days. Most matings occur during the maximum swelling. The gestation period is on average 240 days. Postpartum amenorrhea (absence of menstruation) lasts less than one year and a female may resume external signs of oestrus within a year of giving birth, though the female is probably not fertile at this point. Female bonobos carry and nurse their young for four years and give birth on average every 4.6 years. Compared to common chimpanzees, bonobo females resume the genital swelling cycle much sooner after giving birth, enabling them to rejoin the sexual activities of their society. Also, bonobo females which are sterile or too young to reproduce still engage in sexual activity. Mothers will help their sons get more matings from females in oestrus. Adult male bonobos have sex with infants. Frans de Waal, an ethologist who has studied bonobos, remarked, "A lot of the things we see, like pedophilia and homosexuality, may be leftovers that some now consider unacceptable in our particular society."
Tzolk'in
Another theory is that the 260-day period is the length of human pregnancy. This is close to the average number of days between the "first missed" menstrual period and birth, unlike Naegele's rule which is 40 weeks (280 days) between the "last" menstrual period and birth. It is postulated that midwives originally developed the calendar to predict babies' expected birth dates.
Hipparchus
Hipparchus also studied the motion of the Moon and confirmed the accurate values for two periods of its motion that Chaldean astronomers are widely presumed to have possessed before him, whatever their ultimate origin. The traditional value (from Babylonian System B) for the mean synodic month is 29 days; 31,50,8,20 (sexagesimal) = 29.5305941... days. Expressed as 29 days + 12 hours +  hours this value has been used later in the Hebrew calendar. The Chaldeans also knew that 251 synodic months ≈ 269 anomalistic months. Hipparchus used the multiple of this period by a factor of 17, because that interval is also an eclipse period, and is also close to an integer number of years (4267 moons : 4573 anomalistic periods : 4630.53 nodal periods : 4611.98 lunar orbits : 344.996 years : 344.982 solar orbits : 126,007.003 days : 126,351.985 rotations). What was so exceptional and useful about the cycle was that all 345-year-interval eclipse pairs occur slightly over 126,007 days apart within a tight range of only about ± hour, guaranteeing (after division by 4267) an estimate of the synodic month correct to one part in order of magnitude 10 million. The 345 year periodicity is why the ancients could conceive of a "mean" month and quantify it so accurately that it is even today correct to a fraction of a second of time.
Menstrual cycle
The cessation of menstrual cycles at the end of a woman's reproductive period is termed menopause. The average age of menopause in women is 52 years, with anywhere between 45 and 55 being common. Menopause before age 45 is considered "premature" in industrialised countries. Like the age of menarche, the age of menopause is largely a result of cultural and biological factors; however, illnesses, certain surgeries, or medical treatments may cause menopause to occur earlier than it might have otherwise.
Khul'
When a woman is granted a divorce through khulʿ, she must enter a waiting period known as iddah. During this period, a woman is not allowed to remarry for one menstrual cycle to ensure that she is not pregnant. In case of divorce women has to wait for three menstrual cycles. Most jurists recommend waiting for the three menstrual cycles even for the iddah of a divorce through khulʿ. If a woman has already gone through menopause, she must wait three calendar months. The waiting period for a woman who has irregular periods is dependent on different interpretations. While some jurists believe that a woman should observe the waiting period for three calendar months as well, others believe that a woman should observe the waiting period for nine months. If a woman is pregnant or becomes pregnant during the waiting period, she must observe the waiting period until laying her burden.
Abnormal uterine bleeding
Symptoms include vaginal bleeding that occurs irregular, at abnormal frequency, last excessively long, or is more than normal. Normal frequency of periods is 22 to 38 days. Variation in the length of time between cycles is typically less than 21 days. Bleeding typically last less than 9 days and blood loss is less than 80 mL. Excessive blood loss may also be defined as that which negatively affects a person's quality of life. Bleeding more than six month after menopause is also a concern.
Menstrual cycle
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 (perimenopause) and in women with polycystic ovary syndrome.
Calendar-based contraceptive methods
To find the estimated length of the pre-ovulatory infertile phase, nineteen (19) is subtracted from the length of the woman's shortest cycle. To find the estimated start of the post-ovulatory infertile phase, ten (10) is subtracted from the length of the woman's longest cycle. A woman whose menstrual cycles ranged in length from 30 to 36 days would be estimated to be infertile for the first 11 days of her cycle (30-19=11), to be fertile on days 12-25, and to resume infertility on day 26 (36-10=26). When used to avoid pregnancy, the rhythm method has a perfect-use failure rate of up to 9% per year.
Molad
The molad emtza'i (מולד אמצעי, average "molad", used for the traditional Hebrew calendar) is based on a constant interval cycle that is widely but incorrectly regarded as an approximation of the time in Jerusalem of the mean lunar conjunction. Each "molad" moment occurs exactly 29 days 12 hours 44 minutes and 3+/ seconds (or, equivalently, 29 days 12 hours and 44+/ minutes) after the previous "molad" moment. This interval is numerically exactly the same as the length of the mean synodic month that was published by Ptolemy in the Almagest, who cited Hipparchus as its source. Although in the era of Hipparchus (2nd century BC) this interval was equal to the average time between lunar conjunctions, mean lunation intervals get progressively shorter due to tidal transfer of angular momentum from Earth to Moon, consequently in the present era the "molad" interval is about / of a second too long.
Estimated date of delivery
The estimated date of delivery (EDD), also known as expected date of confinement, and estimated due date or simply due date, is a term describing the estimated delivery date for a pregnant woman. Normal pregnancies last between 37 and 42 weeks.
Trombiculidae
The length of the mite's cycle depends on species and environment but normally lasts two to 12 months. The number of cycles in a year depends on the region. For example, in a temperate region, there might only be three per year, but in tropical regions the cycle might be continuous all year long. Adult harvest mites winter in protected places such as slightly below the soil. Females become active in the spring, and once the ground temperature is regularly above , she lays eggs in vegetation, up to 15 eggs per day. The eggs are round and are dormant for about six days, after which the nonfeeding prelarvae emerge, with only three pairs of legs. After about six days, the prelarva grows into its larval stage.
Irregular menstruation
Alternatively, a single menstruation cycle may be defined as irregular if it is less than 24 days or more than 38 days. If they are regularly shorter than 21 days or longer than 36 (or 35) days, the condition is termed polymenorrhea or oligomenorrhea, respectively.
Woman
Menarche, the onset of menstruation, occurs on average at age 12–13. Many cultures have rites of passage to symbolize a girl's coming of age, such as confirmation in some branches of Christianity, bat mitzvah in Judaism, or even just the custom of a special celebration for a certain birthday (generally between 12 and 21), like the quinceañera of Latin America.
Menstrual synchrony
McClintock's study consisted of 135 female college students who were 17 to 22 years old at the time of the study. They were all residents of a single dormitory, which had four main corridors. The women were asked when their last and second to last menstrual period had started three times during the academic year (which ranged from September to April). They also were asked who (other women in the dormitory) they associated with most and how often each week they associated with males. From these data, McClintock placed women into pairs of close friends and roommates and she also placed them into groups of friends ranging in size from 5 to 10 women. She reported statistically significant synchrony for both her pairwise sorting of women and her group sorting of women. That is, whether women were placed into pairs of close friends and roommates or whether they were placed into larger groups of friends, she reported that they synchronized their menstrual cycles. She also reported that the more often women associated with males, the shorter their menstrual cycles were. She speculated that this may be a pheromone effect paralleling the Whitten effect in mice but that it could not explain menstrual synchrony among women. Finally, she speculated that there could be a pheromone mechanism of menstrual synchrony similar to the Lee-Boot effect in mice.
Irregular menstruation
Irregular cycles or irregular periods is an abnormal variation in length of menstrual cycles. A female usually experiences cycle length variations of up to eight days between the shortest and longest cycle lengths. Lengths ranging between eight and 20 days are considered moderately irregular. Variation of 21 days or more is considered very irregular.
Menstrual synchrony
Following the statistical critiques of Schank, they argued that circular statistics were required to analyze periodic data for the existence of synchrony. However, menstrual cycles are variable in frequency (e.g., 28 or 31 day cycles) and in length. They pointed out that there are no statistical methods for analyzing messy data like this, so they developed Monte Carlo methods for detecting synchrony.
Calendar-based contraceptive methods
Developed by Georgetown University's Institute for Reproductive Health, the Standard Days Method has a simpler rule set and is more effective than the rhythm method. A product called CycleBeads was developed alongside the method to help the user keep track of estimated high and low fertility points during her menstrual cycle. The Standard Days Method may only be used by women whose cycles are usually between 26 and 32 days in length. In this system:
Babirusa
Female babirusa cycle lengths are between 28 and 42 days and estrus last 2–3 days. The litter size for a babirusa is usually one or two piglets.
Pregnancy rate
The time with the highest likelihood of pregnancy resulting from sexual intercourse covers the menstrual cycle time from some 5 days before until 1 to 2 days after ovulation. In a 28‑day cycle with a 14‑day luteal phase, this corresponds to the second and the beginning of the third week. 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 cycle
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 have been known to trigger migraines, especially when the woman who suffers 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 (such as seizures coinciding with the time of menstruation, or coinciding with the time of ovulation), and the frequency with which they occur has not been firmly established. Using one particular definition, one group of scientists found that around one-third of women with intractable partial epilepsy has catamenial epilepsy. An effect of hormones has been proposed, in which progesterone declines and estrogen increases would trigger seizures. Recently, studies have shown that high doses of estrogen can cause or worsen seizures, whereas high doses of progesterone can act like an antiepileptic drug. Studies by medical journals have found that women experiencing menses are 1.68 times more likely to attempt suicide.
The Story of Menstruation
The film uses animated diagrams to detail the menstrual cycle. The film's narrator, who is not identified in the credits, informs the viewer that "there is nothing strange or mysterious about menstruation", and it shows women engaged in such activities as bathing, riding a horse, and dancing during their menstrual cycles. The film's narration by actress Gloria Blondell also provides advice to avoid constipation and depression, and to always keep up a fine outward appearance.
28 (film)
28 is a 2014 Sri Lankan feature drama film directed and produced by Prasanna Jayakody. The film starred by Mahendra Perera and Semini Iddamalgoda in lead roles along with Rukmal Nirosh, Sarath Kothalawala. "28" revolves how three men transport the body of a woman, who was raped and murdered, in an old van. One of the men will find out that the woman is his estranged wife.The film name is given considering that the average menstrual cycle of a woman is around 28 Days. (Which is also equal for the moon to complete one full orbit around earth).
Menstruation
There is debate among medical researchers about the potential long-term impacts of these practices upon female health. Some researchers point to the fact that historically, females have had far fewer menstrual periods throughout their lifetimes, a result of shorter life expectancies, as well as a greater length of time spent pregnant or breast-feeding, which reduced the number of periods experienced by females. These researchers believe that the higher number of menstrual periods by females in modern societies may have a negative impact upon their health. On the other hand, some researchers believe there is a greater potential for negative impacts from exposing females perhaps unnecessarily to regular low doses of synthetic hormones over their reproductive years.
Menstrual cycle
The length of a woman's menstrual cycle typically varies somewhat, with some shorter cycles and some longer cycles. A woman who experiences variations of less than eight days between her longest cycles and shortest cycles is considered to have regular menstrual cycles. It is unusual for a woman to experience cycle length variations of more than four days. Length variation between eight and 20 days is considered as moderately irregular cycles. Variation of 21 days or more between a woman's shortest and longest cycle lengths is considered very irregular.
Common treeshrew
Both sexes of common treeshrews are sexually mature at the age of about three months. In captivity, females give birth for the first time at the age of about 4.5 mo, usually in February. A postpartum oestrus results in more births in April. Their oestrus cycle is eight to 39 days, and the gestation period lasts 40 to 52 days, after which a litter of one to three individuals is born. The newborn offspring weigh about 10 to 12 grams. Females suckle their young every other day, and neglect their young as long as possible. They would not even be able to identify their own young if they did not mark them with the scent produced from glands in their sternum and abdomen. Juveniles leave the nest between 25 and 35 days of age. Longevity of a captive common treeshrew has been recorded as 12 yr and 5 mo.
Estrous cycle
A female dog is usually diestrous (goes into heat typically twice per year), although some breeds typically have one or three cycles per year. The proestrus is relatively long at 5 to 9 days, while the estrus may last 4 to 13 days, with a diestrus of 60 days followed by about 90 to 150 days of anestrus. Female dogs bleed during estrus, which usually lasts from 7–13 days, depending on the size and maturity of the dog. Ovulation occurs 24–48 hours after the luteinizing hormone peak, which is about somewhere around the fourth day of estrus; therefore, this is the best time to begin breeding. Proestrus bleeding in dogs is common and is believed to be caused by diapedesis of red blood cells from the blood vessels due to the increase of the estradiol-17β hormone.
Short-beaked common dolphin
Similar to humans, the short-beaked common dolphin is viviparous. Though they have the ability to carry twins, triplets, etc., they usually only carry one baby at a time. The Short-beaked common dolphin has a gestation period of 10 to 11 months. The newborn calf has a length of between and weighs about . For the Black Sea population, weaning occurs at between 5 and 6 months, but occurs later (up to about 19 months) in other areas. Typical interbirth interval ranges from 1 year for the Black Sea population to 3 years for eastern Pacific Ocean populations. Age of sexual maturity also varies by location, but can range between 2 and 7 years for females and 3 and 12 years for males. Common short-beaked dolphins have been observed to engage in oral sex, intimating that they – like chimpanzees and humans – engage in sexual activities for pleasure.
Cougar
Females reach sexual maturity between one-and-a-half to three years of age. They typically average one litter every two to three years throughout their reproductive lives, though the period can be as short as one year. Females are in estrus for about 8 days of a 23-day cycle; the gestation period is approximately 91 days. Females are sometimes reported as monogamous, but this is uncertain and polygyny may be more common. Copulation is brief but frequent. Chronic stress can result in low reproductive rates when in captivity as well as in the field.
Calendar-based contraceptive methods
The postovulatory (luteal) phase has a normal length of 12 to 16 days, and the rhythm method formula assumes all women have luteal phase lengths within this range. However, many women have shorter luteal phases, and a few have longer luteal phases. For these women, the rhythm method formula incorrectly identifies a few fertile days as being in the infertile period.
Extended cycle combined hormonal contraceptive
Although it was evident that the pill could be used to suppress menstruation for arbitrary lengths of time, the original regimen was designed to produce withdrawal bleeding every four weeks to mimic the menstrual cycle.
Menstrual cycle
Breastfeeding causes negative feedback to occur on pulse secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH). Depending on the strength of the negative feedback, breastfeeding women may experience complete suppression of follicular development, but no ovulation, or normal menstrual cycle may resume. Suppression of ovulation is more likely when suckling occurs more frequently. The production of prolactin in response to suckling is important to maintaining lactational amenorrhea. On average, women who are fully breastfeeding whose infants suckle frequently experience a return of menstruation at fourteen and a half months postpartum. There is a wide range of response among individual breastfeeding women, however, with some experiencing return of menstruation at two months and others remaining amenorrheic for up to 42 months postpartum.
Oligomenorrhea
Oligomenorrhea (or oligomenorrhoea) is infrequent (or, in occasional usage, very light) menstruation. More strictly, it is menstrual periods occurring at intervals of greater than 35 days, with only four to nine periods in a year. Menstrual periods should have been regularly established before the development of infrequent flow. The duration of such events may vary.
Menstrual synchrony
Ziomkiewicz conducted a study with 99 Polish college women living in two dormitories. Thirty six of the women lived in 18 double rooms and sixty three lived in 21 triple rooms. Women recorded their menstrual cycle onsets on menstrual calendars provided to them and 181 days' worth of menstrual cycle data were collected. The mean menstrual cycle length was 30.5 days (SD = 4.56).
Ovarian apoplexy
In the ovaries of sexually mature women, follicles grow, and oocyte matures in them, to prepare for potential fertilization. As a menstrual cycle progresses, a dominant follicle begins to stand out, and in the middle of the menstrual cycle it reaches its maximum size of about 20mm. Then the follicle ruptures, releasing a mature egg (ovulation). The location from which the follicle emerges then forms a temporary cyst, called the corpus luteum, which produces hormones to continue the menstrual cycle and mature the uterine lining. This is the normal ovarian cycle.
Amenorrhea
Certain medications, particularly contraceptive medications, can induce amenorrhoea in a healthy woman. The lack of menstruation usually begins shortly after beginning the medication and can take up to a year to resume after stopping a medication. Hormonal contraceptives that contain only progestogen like the oral contraceptive Micronor, and especially higher-dose formulations like the injectable Depo Provera commonly induce this side effect. Extended cycle use of combined hormonal contraceptives also allow suppression of menstruation. Patients who use and then cease using contraceptives like the combined oral contraceptive pill (COCP) may experience secondary amenorrhoea as a withdrawal symptom. The link is not well understood, as studies have found no difference in hormone levels between women who develop amenorrhoea as a withdrawal symptom following the cessation of COCP use and women who experience secondary amenorrhoea because of other reasons. New contraceptive pills, like continuous oral contraceptive pills (OCPs) which do not have the normal 7 days of placebo pills in each cycle, have been shown to increase rates of amenorrhoea in women. Studies show that women are most likely to experience amenorrhoea after 1 year of treatment with continuous OCP use.
Estradiol valerate/hydroxyprogesterone caproate
EV/OHPC as a combined injectable contraceptive has a relatively short duration and is associated with a high incidence of menstrual irregularity, for instance polymenorrhea (short and hence fast cycles). This may be unacceptable to many women. Twice-monthly administration of half doses has not been found to improve breakthrough bleeding, though cycle length increased to 20 to 24 days.
Menstrual Hygiene Day
May 28 has symbolic meaning. May is the 5th month of the year and women menstruate an average of 5 days every month. Also, the menstrual cycle averages 28 days.
Polycystic ovary syndrome
If a regular menstrual cycle is not desired, then therapy for an irregular cycle is not necessarily required. Most experts say that, if a menstrual bleed occurs at least every three months, then the endometrium (womb lining) is being shed sufficiently often to prevent an increased risk of endometrial abnormalities or cancer. If menstruation occurs less often or not at all, some form of progestogen replacement is recommended. An alternative is oral progestogen taken at intervals (e.g., every three months) to induce a predictable menstrual bleeding.