Fehring, R. J., Schneider, M., & Raviele, K. (2006). Variability in the phases of the menstrual cycle. Journal of Obstetric, Gynecologic, and Neonatal Nursing : JOGNN, 35(3), 376-384. https://doi.org/10.1111/j.1552-6909.2006.00051.x
Fehring RJ, Schneider M, Raviele K. Variability in the phases of the menstrual cycle. J Obstet Gynecol Neonatal Nurs. 2006;35(3):376-384. doi:10.1111/j.1552-6909.2006.00051.x
Fehring, Richard J., et al. "Variability in the phases of the menstrual cycle." Journal of Obstetric, Gynecologic, and Neonatal Nursing : JOGNN, vol. 35, no. 3, 2006, pp. 376-384.
42.5% of the healthy, regularly cycling women in a monitor-charted study had cycle lengths that differed by more than 7 days. The study followed 141 women across 1,060 cycles. The days before ovulation contributed most of that variation.
About 4 in 10 women had cycle lengths that differed by more than 7 days within the same woman. Source: Fehring RJ et al., 2006, PMID 16700687.Study at a glance, cohort study of 141 healthy, regularly cycling women: Healthy, regularly cycling women's cycle phases vary widely. Source: Fehring RJ et al., 2006, PMID 16700687.
Key Findings
Cycles averaged 28.9 days, and 95% of cycles fell between 22 and 36 days.
42.5% of the women had cycle lengths that differed by more than 7 days within the same woman.
The follicular phase differed by more than 7 days in 33.6% of women. The luteal phase, the days after ovulation, did so in 9%.
In this sample, 95% of cycles had all 6 fertile days between cycle days 4 and 23. Only 25% of women had all 6 fertile days between days 10 and 17.
Interpretation
This cohort study followed 141 healthy, regularly cycling women, aged 19 to 44, across 1,060 cycles over about a year, with each woman contributing 3 to 13 cycles. A urinary luteinizing hormone surge marked the day of ovulation. The authors note that cycle variation is larger in the years just after menarche and in the years before menopause. Most women in this sample were aged 25 to 35. The findings support larger studies of cycle variability across different life stages.
RRM Context
Fertility awareness tracks each woman's own signs of ovulation. In this sample, only 25% of women had all 6 fertile days inside days 10 to 17. The authors report that biological markers let a woman track her fertile phase even when cycles vary. They link greater-than-normal variability to possible health problems.
Our editorial summary of this paper, not the article's abstract.
Abstract
Objective
To determine variability in the phases of the menstrual cycle among healthy, regularly cycling women.
Design
A prospective descriptive study of a new data set with biological markers to estimate parameters of the menstrual cycles.
Participants
One hundred forty one healthy women (mean age 29 years) who monitored 3 to 13 menstrual cycles with an electronic fertility monitor and produced 1,060 usable cycles of data.
Measures and Outcomes
Variability in the length of the menstrual cycle and of the follicular, fertile, and luteal phases, and menses. The estimated day of ovulation and end of the fertile phase was the peak fertility reading on the monitor (i.e., the urinary luteinizing hormone surge).
Results
Mean total length was 28.9 days (SD = 3.4) with 95% of the cycles between 22 and 36 days. Intracycle variability of greater than 7 days was observed in 42.5% of the women. Ninety-five percent of the cycles had all 6 days of fertile phase between days 4 and 23, but only 25% of participants had all days of the fertile phase between days 10 and 17.
Conclusions
Among regularly cycling women, there is considerable normal variability in the phases of the menstrual cycle. The follicular phase contributes most to this variability.
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