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Cited by 375Menstrual Health and DisordersHypothalamic control of reproductive hormonesReproductive Health and Contraception

The length and variability of the human menstrual cycle

Chiazze, Leonard·1968·JAMA: The Journal of the American Medical Association
DOI 10.1001/jama.1968.03140060001001
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Abstract

The Center for Population Research collected 30,655 recorded menstrual cycles from 2,316 women. Ninety-five percent of all cycles were between 15 and 45 days long. The mean and standard deviations for the total number of cycles were 29.1 and 7.46, respectively. Cycle lengths between 15 and 45 days averaged 28.1 days with a standard deviation of 3.95 days. Variability of menstrual-cycle lengths is highest for women under 25 years of age and declines steadily to reach a minimum for ages 35 to 39. It is then followed by a slight increase for women aged 40 to 44. The pattern of variability by age is demonstrated equally well by the percent of cycles between 25 and 31 days in length as by the standard deviation.

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Crossref · 10.1001/jama.1968.03140060001001

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  • Although the average length of a woman's menstrual cycle is 28 days, there is considerable intra- and inter-individual variation in cycle lengths as well as changes in a woman's own personal cycle with time.

    “Although the average length of a woman’s menstrual cycle is 28 days, there is considerable intra- and inter-individual variation in cycle lengths as well as changes in a woman’s own personal cycle with time (Treloar et al. 1967; Chiazze et al. 1968; Vollman 1977; Münster et al. 1992; Park et al. 2007; Johnson et al. 2009).”

    From Real-life insights on menstrual cycles and ovulation using big data (2020) · cites this paper as Chiazze et al. 1968

  • The results are in alignment with reference studies.

    “These results are in alignment with those of reference studies.3,6,9”

    From Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles (2019) · cites this paper as [9]

  • With increasing age, cycle length reduces and the timing of ovulation becomes earlier; the variation of a woman's cycle length reduces with age until menopause.

    “With increasing age, cycle length reduces and the timing of ovulation becomes earlier; the variation of a woman’s cycle length reduces with age until menopause.5,6,8,9”

    From Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles (2019) · cites this paper as [9]

  • The day of ovulation varies on an inter- and intra-individual level.

    “The day of ovulation varies on an inter- and intra-individual level.”

    From Real-life insights on menstrual cycles and ovulation using big data (2020) · cites this paper as Chiazze et al. 1968

  • The cycle characteristics described in this study are consistent with previous findings on research cohorts.

    “The cycle characteristics described in this study are consistent with previous findings on research cohorts (Chiazze et al. 1968; Vollman 1977; Münster et al. 1992; Johnson et al. 2009; 2018), indicating that previous clinical findings are still reflective of cycle characteristics of today’s population of women who are seeking to conceive.”

    From Real-life insights on menstrual cycles and ovulation using big data (2020) · cites this paper as Chiazze et al. 1968

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Authors
Chiazze, L.
Corresponding author
Chiazze, Leonard
Venue
JAMA: The Journal of the American Medical Association
Publisher
American Medical Association (AMA)
Published
1968-02-05
Volume
203
Issue
6
Pages
377
ISSN
  • 0002-9955 (ISSN-L)
  • 0098-7484
DOI
10.1001/jama.1968.03140060001001
OpenAlex
W2027829650
Cited by
374
References
12
Citations by year
2026: 4 · 2025: 8 · 2024: 4 · 2023: 10 · 2022: 11 · 2021: 10 · 2020: 14 · 2019: 11 · 2018: 7 · 2017: 7 · 2016: 10 · 2015: 15 · 2014: 12 · 2013: 21 · 2012: 12
FWCI
27.35
Type
journal article
Language
en
Open access
closed
Locations
  • JAMA (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Menstrual Health and Disorders
  • Health Sciences › Medicine › Reproductive Medicine › Hypothalamic control of reproductive hormones
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Reproductive Health and Contraception
Keywords
menstrual cycle length, menstrual cycle variability, cycle length distribution, age differences, women's reproductive health
MeSH terms
Adult, Age Factors, Female, Humans, Menopause, Menstruation, Middle Aged, Prospective Studies, Statistics as Topic, Time Factors

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