The Duration of Menstrual Blood Loss

The Duration of Menstrual Blood Loss: History

Please note this is an old version of this entry, which may differ significantly from the current revision.

Subjects: Obstetrics & Gynaecology | Reproductive Biology | Primary Health Care

Contributor:

The duration of bleeding is not necessarily linked to the amount of loss but may be influenced by age, ethnicity, habitus, region and altitude of residence, dieting and stress. The onset of bleeding has been linked to declining steroid production by the corpus luteum. There remains considerable controversy around the extent of endometrial shedding at menstruation. This is likely to vary within and between women. The significance of a change from previous patterns, very short or prolonged bleeding, days of light loss or spotting before or after days of bleeding, or of bleed-free days that punctuate flow, remain poorly understood.

menstruation
menstrual bleeding
duration of bleeding
menstrual phase
endometrium

1. Introduction

The impact of abnormal uterine bleeding and the link between menstruation and ovarian function have long been recognised. Most of clinical data and research have so far been focused on the amount of blood loss and, to a lesser extent, on cyclicity [1,2]. Women often raise the question with clinicians as to the reasons why they bleed for shorter or longer days, but in contrast with the question of the amount of blood loss, the issue seems largely set aside and rarely, if ever, considered in the literature or clinical guidelines. Although much of this is now subsumed under the broad category of abnormal uterine bleeding (AUB), early descriptions of menstrual cycles utilised specific nomenclature when referring to the quantity of loss and its regularity. By contrast, less attention has been paid to the duration of bleeding, the factors that enable its cessation within an expected ‘normal’ timeframe, or to aberrations that entail prolonged or short bleeding. Most publications refer to the duration of bleeding only in terms of average or range. Most recent studies that address changes in the menstrual cycle in relation to COVID-19 vaccination do not comment on the duration of bleeding [3,4,5]. The duration of bleeding is recognised as having an impact on patients and on their satisfaction with treatment of menstrual abnormalities [6]. An international initiative proposed that bleeding be classified as normal if its duration is between 4.5 and 8 days, prolonged if >8 days and shortened if <4.5 days [7]. The original FIGO classification system includes prolonged duration of bleeding under the heading Abnormal Uterine Bleeding but does not propose cut-off points [8]. The modified classification does not refer to shortened duration but uses >8 days as the upper limit for normal [9]. The derivation of these ranges remains uncertain (Table 1). Interestingly, women regarded 3 days as the optimal duration of bleeding [10]. The duration of bleeding and its amount are not always linked, and little is understood about the significance of the lighter loss that sometimes occurs before or after the recognised menstrual flow. Nevertheless, in one report, treatment of women with heavy menstrual bleeding (HMB) using mefenamic acid or misoprostol resulted in reduction of both the amount of loss and its duration [11]. Factors that may contribute to prolonged uterine bleeding may reside in disturbances of the dynamics that control the onset of bleeding or those responsible for endometrial shedding or its restoration. The term ‘regenerative phase’ of the menstrual cycle which was used in the past to refer to the stage when endometrial re-epithelialization takes place is rarely used in the modern literature. Zhang et al. stated that women who reported their bleeding to last <4 or >5 days had lower fecundity ratio compared to those who reported 4–5 days of bleeding [12].

Table 1. The adopted cut-off points for normal duration of menstrual blood loss.

Study	Suggested Cut-Off for Normal
Meigs (1849) [13]	Each woman has her own cycle
Tauszky (1879) [14]	10 days can be considered normal
Fraser et al. (2007) [7]	Between 4.5–8 days
Munro et al. (2018) [9]	upper limit of normal > 8 days as, no lower limit
Bastianelli et al. (2023) [10]	Women reported preference of 3 days

2. Assessing the Duration of Bleeding

The variation between women in the duration of menstrual bleeding has long been recognised. Meigs (1849) who, like many of his contemporaries, attributed the onset of bleeding to ovulation, wrote that ‘in the duration of the flow, as well as in the number of fluidounces discharged, each woman obeys a law of her own nature’ [13]. Meigs went on to suggest that no action is required in relation to such variation [13]. Early writers recognised the variation in the duration of bleeding, and the view was held that 10 days of bleeding should be pronounced as normal menstruation if the woman was otherwise well [14].

Considerable effort was spent during the 1960–1970s on agreeing on methods to assess menstrual blood loss. The impetus for this stemmed from the need to develop and compare the then emerging methods of contraception. One such effort was the workshop held at the University of Exeter, UK, in March 1976. This workshop had as an aim reaching agreement on a prospective method for data collection that relied on easily obtained information. The emphasis was placed on simplicity of both the definitions and analytical methods [15,16]. The 90-day reference period method was adopted by the workshop to avoid the difficulty entailed in accounting for episodes of intermenstrual bleeding that can occur during the menstrual cycle. The proposal drawn at the workshop also included drawing a distinction between ‘bleeding’ and ‘spotting.’ Statistical comparisons were made based on features such as the average number or average duration of episodes of bleeding and the difference between study groups, rather than on cyclicity or reproducibility of cycles for the individual. No particular emphasis was placed on the duration of what might constitute ‘menstrual loss’ [15]. Spotting was defined in terms of light bleeding where sanitary protection is not used. It is interesting to note that workshop participants debated the inclusion of spotting not from a pathophysiological standpoint, but because of the likely impact this may have on the analysis and based on their appreciation of women’s behaviour or attitude. Rodriguez et al. pointed out that the appropriateness and reliability of the distinction between bleeding and spotting can vary and, as such, should be judged by each individual investigator [17]. Despite it being still widely used, the term ‘spotting’ that is used in relation to menstrual loss is curious because this is not the manner in which light bleeding manifests clinically.

The 90-day reference period [17] considers the duration of bleeding in terms of bleeding episodes or as an aggregated mean duration rather than in terms of its tendency to recur in subsequent cycles. Thus, while analysis based on reference period avoids the difficulties entailed in defining the menstrual cycle, it obscures cyclicity, cycle predictability and the relation between bleeding that may precede or follow menstruation or hormone withdrawal, and other bleeding episodes.

3. Identifying the Onset of Bleeding and Its Cessation

The onset and end of menstrual bleeding continues to be determined through the recognition by the woman herself. Vollman (1977) observed that this carries a methodological error of one day when it comes to determining the onset of bleeding because little is known about the interval between the appearance of blood at the external cervical os and subjective perception of onset of menstruation [18]. The same can be said about the end of bleeding. Furthermore, as recognised in relation to neonatal uterine bleeding, a distinction could be made based on whether bleeding is observed macroscopically or biochemically. Defining the exact onset point of endometrial breakdown rather than the point of manifest blood loss has relevance to research. Early investigators pointed out that the difficulty in defining the onset of menstruation impacts the interpretation of histological features [19].

As referred to above, defining the onset of bleeding remains problematic. Li et al. (2020) defined a period as ‘the sequential days of bleeding (greater than spotting and within 10 days after the first greater-than-spotting bleeding event) unbroken by >1 day on which only spotting, or no bleeding occurred’ [20]. In the study by Bull et al., participants were instructed not to log very light bleeding that may occur just before the period, but to wait until the flow increases. In this study, bleed length was defined as the number of consecutive days of bleeding excluding spotting, and spotting was defined as very light bleeding (a few drops of blood) or the appearance of brown/pink fluids [21]. There does not appear to be any scientific rationale for excluding days of spotting that may precede or follow heavier loss.

Another feature identified in early studies of uterine bleeding is that the shed material remains in the uterine cavity for some time. This view, however, was based on a limited number of observations from normal uteri. Dallenbach-Hellweg pointed out that there are great variations in the length and the extent of shedding and of shrinkage without shedding [22]. Thus, some women shed only the upper functionalis layer, others the lower functionalis and others yet do not shed the endometrium at all. This is perhaps linked to the phenomenon defined as ‘silent menstruation’ [23,24].

4. Assessing Variability

When it comes to comparing contraceptives, the assumption has been made that minor variations in the length of the 24 h period (indicating that duration can be considered based on the day not the hour of onset) and in the exact start and end of bleeding are not important, provided there is consistency in applying an agreed rule [25]. However, such variations can affect studies concerned with the mechanisms that control blood loss. There is lack of clarity on how an isolated day of manifest bleeding or ‘spotting’ followed or preceded by a bleed free day or days should be included in the analysis of menstrual cycles [25]. Such distinctions are particularly important when examining variations in the duration of bleeding because of the narrow range of variability. Interestingly, bleeding commenced during the night or in the first 4 h after rising in 70.4% of cycles, and premenstrual spotting for more than 3 h was reported in 67% of women [26].

There are limited reports that address the duration of bleeding. Goldzieher et al. reported on 524 cycles (500 of which were ovulatory) that were recorded by 109 healthy women. Ovulation was detected by assessing the basal body temperature. The authors reported that the duration of the progestogenic phase was fairly consistent (69.5% falling between 11 and 14 days), and none were shorter than 8 days or longer than 19 days. The duration of bleeding was available in 481 cycles. In 68.4% of cases, bleeding lasted for 3–5 days, and in 95.4% of cases, bleeding lasted for 3–7 days [27]. The study did not report on cycle-to-cycle variability for individuals. In the study by Najmabadi et al. (2020) that reported on the duration of bleeding in women with no known subfertility (n = 537) who were followed up for one year (n = 2645 cycles), the mean duration of bleeding was 6.2 (±1.5) days, but bleeding duration ranged from 3 to 15 days. The within-woman difference in the duration of bleeding was >3 days in 11.6% of women. The study found no difference between women based on their age (<30 years vs. ≥30 years) or parity (nulliparous vs. parous) [28].

Large-scale prospective studies [18,29,30,31,32] also used summary data on menstrual cycle length across the calculated measures of central tendency stratified by age. They measured population mean and range, but not cycle-to-cycle variability for individual women. A different approach was taken by Harlow and Zeger (1991) in their analysis of menstrual diaries from university students experiencing spontaneous cycles [33]. The authors calculated the transition probabilities of any given cycle length to a different cycle length. The most probable transition for a segment of any length (except for segments <17 days) was to a segment of 26–34 days. Here, the term ‘menstrual segment’ was used in reference to menstrual cycle to acknowledge that diary data cannot distinguish between menstrual and non-menstrual bleeding episodes. The longest and shortest segments had greater probabilities than segments closer to the mean of being followed by either a short or a long segment. Harlow and Zeger (1991) reported that within-women variability in cycle length is approximately twice as large as variability between women [33]. Habiba et al. (1996) used this approach when assessing the transition probability and the likelihood that a particular cycle in women on cyclical hormone replacement therapy (HRT) is followed by a cycle of similar or of different length [34]. There are no comparable analyses of the cycle-to-cycle changes in the duration of bleeding. Treloar et al. reported on a major study of menstrual bleeding patterns in women who recorded their bleeding for up to 30 years [30]. The authors pointed out that the occurrence of spotting just prior to the first day of flow, which was more common in the premenopausal years, presented a problem for determining the onset of menstruation [30]. But neither this study nor the other major study by Vollman provided an analysis of the duration of bleeding [18].

5. The Relation between the Amount of Loss and Its Duration

The relation between the duration and the amount of blood loss has been subject to debate. In a population study involving 362 women aged between 15 and 50 years whose blood loss was measured daily, Rybo reported that bleeding for more than a week was linked to heavy menstrual loss. Women with menorrhagia experienced 69% of the total loss during the first 2 days and 86% in the first 3 days of the period. Women who bled <80 mL per cycle lost 79% during the first 2 days and 92% during the first 3 days of the period [35]. Another study in a healthy population found limited correlation between the amount of loss and its duration [36]. Other studies found no relation between the duration of menstruation and the total amount of blood loss in women with menorrhagia [37,38]. Another study that included women with normal menstruation and women with menorrhagia found little relation between the amount of loss and its duration [39]. Women with inherited bleeding disorders were reported to experience longer duration of bleeding and shorter cycles [40]. However, the authors pointed out that the difference may be related to different response rates amongst participants [40]. Most blood loss occurs within the first 48–72 h of the onset of bleeding, which may explain the lack of correlation between the amount and duration of loss.

6. Factors That Affect the Duration of Bleeding

Bull et al. described the characteristics of 612,613 ovulatory menstrual cycles from real-world users of an electronic menstrual record. The mean duration of bleeding was 4.0 ± 1.5 days. The duration of bleeding was shorter by 0.5 days for cycles < 21 days long and longer by 0.2 days for cycles > 35 days long [21]. The bleeding duration was 4.2 ± 1.4, 4.0 ± 1.4, 3.9 ± 1.5, 3.8 ± 1.5 and 3.7 ± 1.5 days for the age groups of 18–24, 25–29, 30–34, 35–39 and 40–45 years, respectively. The duration of bleeding varied in relation to body mass index (BMI) and was statistically significantly longer by 0.2 days (95% CI: 0.18–0.22 days) in the 15–18.5 BMI group and shorter by 1 day in the 35–50 BMI group (Table 2).

Table 2. The relation between the duration of menstrual blood loss and body mass index [21].

BMI Range	Number of Cycles	Duration of Bleeding (Mean ± Std)
15–18.5	25,735	4.2 ± 1.5 *
18.5–25	431,667	4.0 ± 1.5
25–30	100,228	3.9 ± 1.4 *
30–35	26,483	3.9 ± 1.4 *
35–50	12,011	3.0 ± 1.5 *
All cycles	621,613	4.0 ± 1.5

* p = < 0.0001 compared to all reported cycles.

The duration of bleeding can vary from cycle to cycle for individuals as well as between women. In relation to the latter, the mean duration of bleeding episodes was reported to be lower in women with higher ponderal index [21,46]. However, two reports that relied on retrospective recollection linked indices of obesity to prolonged bleeding [47,48]. The study by Parker et al. asked teenage girls about their ‘usual’ menstrual cycle and reported the average duration of bleeding as 5.93 days [49]. Region- [50,51,52,53], age-, [54,55] and altitude-related [56] variability in duration of flow have also been reported.

There is no agreement on the relation between bleeding duration and the occurrence of ovulation. This may be related to difficulties in detecting ovulation because distinguishing anovulation based on clinical features is unreliable. Anovulation has been linked to short or long cycles. Anovulation is believed to be more common at the beginning and the end of reproductive years. Bleeding linked to anovulation is related to exposure to unopposed oestrogen [57]. In a study of the menstrual bleeding patterns of regularly menstruating women, Dasharathy et al. reported longer duration of bleeding in ovulatory compared to anovulatory cycles (5.4 days vs. 4.5 days; p = 0.025) [41]. However, this estimate was derived from a subset of their study participants. In another study involving women approaching the menopause, both short (1–3 days) and prolonged (>8 days) bleeding were associated with anovulation in 18% and 23% of cases, respectively. A lower incidence of anovulation (9.8%) was reported in cycles where the bleeding lasted 4–7 days [58]. Both studies were based on one menstrual cycle and reported a lower incidence of heavy menstrual loss in women with anovulatory cycles [41,58]. The study design does not enable commenting on cycle-to-cycle variability.

Examining the impact of hormonal status on bleeding is necessarily linked to the changes in hormone levels during the cycle and to the timing of ovulation and regression of the corpus luteum. The variability in menstrual cycle and in the timing of the LH peak are well recognised [59,60,61,62]. In another study of healthy women, the length of the luteal phase ranged from 9 to 20 days [61]. Cole et al. calculated the mean luteal phase to be 13.2 ± 2.0 days (95% CI 9–17 days). The individual variance in the luteal phase was 2.6 ± 3.1 days [63]. The authors attributed the tighter range in their study to the exclusion of atypical cases, such as those with no clear LH peak (attributed to anovulation), cases with exceptionally elevated LH and women with >40-day cycles [63].

Higher FSH was linked to heavier and more prolonged bleeding and higher progesterone levels to heavier loss [41]. For every log unit increase in FSH, menses length increased by 3% (survival time ratio 1.03, 95% CI: 1.01–1.05). There was no association between LH, progesterone or oestrogen and the duration of bleeding when adjusted for confounders [41]. On the other hand, Van Voorhis et al. (2008) found that after correction for anovulation, daily and integrated hormone production had no independent effect on the duration of bleeding in the subsequent cycle [58].

Harlow and Campbell studied menstrual diaries collected over one year from healthy women aged 17–19 years. The median duration of bleeding was 5 days, but cycles varied widely (range 1–19 days, 97% between 3–8 days). The duration of bleeding was not associated with the length of the preceding cycles, history of long cycles, change in body weight, college entry, or being away from home [64]. Late menarche was linked to a slight increase in the duration of bleeding. Women with low weight-for-height (using Benn’s index [65]) [64] bled for about 0.4 days longer. Bleeding was 0.15 days longer in women at the 90th centile of perceived stress. Dieting reduced bleeding by about 0.5 days and moderate-to-hard exercise reduced bleeding by 0.23 days. Harlow and Campbell (1994) speculated that dieting prolonged bleeding through increasing anovulatory cycles [66].

The duration of bleeding was considered in the WHO prospective study of bleeding patterns at the onset of puberty in girls from different ethnic background. Participants who were 11–15 years old at recruitment were followed up for 2 years [67]. Days of spotting that were not separated by more than one day were counted as days of bleeding. The mean duration of bleeding of all participants was 4.7 days (SD = 1.8) and for those who reached menarche before recruitment it was 4.9 days (SD = 1.4). There was a wider variation in the duration of bleeding immediately following menarche. The duration of bleeding varied between girls from different countries: participants in Hong Kong bled for 6 days (85.8% of cycles were between 3 and 7 days) compared to 4.3 days (90.7% between 3 and 7 days) for participants in Colombo, Sri Lanka [67].

Harlow and Campbell compared menstrual bleeding patterns of American women of African (AfA) and European (EuA) descent. Most (85%) participants who were between 12 and 14 years reported 12 cycles. The median duration of bleeding was 5 days (range 1–34 days), 96.5% of bleeding episodes lasted 3–8 days; 15 (6.5%) participants reported having at least one episode of bleeding of >10 days. Ethnicity was the strongest determinant of bleeding duration which was longer in EuA (5.6 days) compared to AfA (5.1 days). For AfA, low and high body mass were linked to shorter bleeding (0.3 and 0.2 days, respectively). For EuA, low body mass increased the duration of bleeding by 0.25 days, but high body mass had no impact. Stress affected the two groups differently. Being at the 90th centile of perceived stress reduced bleed duration by 0.1 days in EuA but had no impact on AfA. Dieting decreased bleed duration by about 0.1 days. The duration of bleeding was slightly longer in those who had late menarche, but was unaffected by exercise, previous cycle length or gynaecologic age [67].

Studies that compared bleeding patterns among contracepting and non-contracepting women used the 90-day bleeding interval. Belsey and Farley (1988) reported a world-wide study and found that bleeding patterns were more closely related to women’s region of residence than to any other factor [26]. For instance, European women using the ovulation detection method of contraception tended to have more bleeding/spotting days than women in other regions. The reason for this is unclear, but it was proposed that it may be related to the way women completed their diaries. It is also possible that the duration of bleeding is influenced by age, altitude, and weight [25,66,68].

The duration of bleeding may be subject to hypothalamic-pituitary control. In a group of healthy nulliparous women aged 18–23 years, Nikolova et al. reported that menstrual cycle length ranged between 23 and 31 days in left-handed women and between 24 and 35 days in right-handed women (p < 0.001) [69]. The duration of bleeding (4.69 ± 0.05) days was significantly shorter in left-handed than right-handed women (5.75 ± 0.004, p < 0.001). This observation may be explained by an association between left-handedness and higher testosterone and oestradiol levels [70]. Uterine factors may also affect the duration of bleeding. In one study, women with self-reported past diagnosis of fibroids had longer duration of bleeding [58]. The duration and quality of sleep and fatigue have been linked to menstrual cycle irregularity and to the quantity of blood loss, but whether these factors affect the duration of bleeding has not been reported [71]. The duration of bleeding was not affected by the administration of chamomile (traditionally believed to affect menstruation) capsules to a group of university students [72]. The duration of bleeding is linked to obesity in some studies [47,48,73], but not in others [74]. Exposure to high concentration of organophosphate pesticides has been linked to shorter duration of bleeding [75]. Summary of factors that may be linked to the duration of bleeding is provided in Table 3.

Table 3. The main findings in studies that commented on factors linked to the duration of bleeding.

Study	Observation Related to Duration of Bleeding
Bastianelli et al. (2023) [10]	Women regard 3 days as the optimal duration of bleeding
Zhang et al. (2017) [12]	Women who reported their bleeding to last <4 or >5 days had lower fecundity ratio compared to those who reported 4–5 days of bleeding
Najmabadi et al. (2020) [28]	No difference in duration of bleeding based on age (<30 years vs ≥30 years) or parity (nulliparous vs parous)
Belsey and Pinol (1997) [29]	Mean duration reduced from 6.6 days at 15 y, to 6.0 days by 20 y and remained largely unchanged until age 49 y
Dasharathy et al. (2012) [41]	Longer duration of bleeding in ovulatory compared to anovulatory cycles
Zurawiecka et al. (2021) [44]	No difference in the duration of bleeding between women with early, average, or late menarche
Mao et al. (2021) [45]	Prolonged bleeding in underweight and shorter bleeding in obese women
Kafaei-Atrian et al. (2019) [48]	Duration of bleeding had a significant relationship with weight, and the circumference of waist, hip and arm. A significant relationship between duration and waist-to-height, waist-to-hip, hip-to-height and arm-to-height ratios
Van Voorhis et al. (2008) [58]	Self-reported past diagnosis of fibroids linked to longer duration of bleeding
Harlow and Campbell (1994) [64]	The duration of bleeding not associated with the length of the preceding cycles, history of long cycles, change in body weight, college entry, or being away from home. Slight increase if late menarche. Longer bleeding if low weight-for-height.
WHO Task Force (1986) [67]	The duration of bleeding varied between countries and is slightly longer if late menarche. Unaffected by exercise, previous cycle length or gynecologic age.
Nikolova et al. (2003) [69]	The duration of bleeding (4.69 ± 0.05 days) was significantly shorter in left-handed compared to right-handed women (5.75 ± 0.004 days)
Mollabashi et al. (2020) [72]	Duration of bleeding not affected by Chamomile
Chang et al. (2009) [73]	Duration of bleeding linked to obesity
Tayebi et al. (2018) [74]	Link between duration of bleeding and obesity not confirmed
Zhang et al. (2020) [75]	Exposure to high concentration of organophosphate pesticides linked to shorter duration of bleeding
Wood et al. (1979) [76]	Based on patient recollection, the duration of bleeding was 1–7 days and 3% of women bled for >7 days
Kirchengast (1994) [77]	The post-cephalic height and length dimensions were positively correlated with the duration of bleeding
Fakeye and Adegoke (1994) [78]	Prolonged bleeding (≥8 days) occurred in less than 5% of postmenarcheal schoolgirls
Vercellini et al. (1997) [79]	The duration of bleeding was longer (mean difference 0.33 days) in women with endometriosis
Bata (2012) [80]	The duration of bleeding in 73.6% of secondary school students was between 4–7 days.
Rigon et al. (2012) [81]	In women and girls aged (13–21 years), the average duration of bleeding was <4 days in 3.2% of participants and >6 days in 19% of participants
Farahmand et al. (2020) [82]	No difference in the duration of bleeding in postmenarcheal girls with different height centiles
Ansong et al. (2020) [83]	International students in China who had high levels of stress reported abnormal duration of bleeding
Charis et al. (2022) [84]	In women recovering from spinal cord injury, the mean duration of bleeding was lower (4.28 ± 0.96 days) compared to the duration of bleeding before the injury (4.88 ± 0.4 days)

This entry is adapted from the peer-reviewed paper 10.3390/reprodmed4030015

© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license; additional terms may apply. By using this site, you agree to the Terms and Conditions and Privacy Policy.