Human reproduction (Oxford, England), 39(11), 2565-2574, 2024
Prospective 1-year assessment of within-woman variability of follicular and luteal phase lengths in healthy women prescreened to have normal menstrual cycle and luteal phase lengths
Sonia Shirin, Azita Goshtasebi , Sarah Henry
Jerilynn C Prior
Author affiliations (3)
University of British Columbia, Vancouver, BC, CanadaROR
UBC Centre for Menstrual Cycle and Ovulation Research , Vancouver, BC,
What is the relative length variance of the luteal phase compared to the follicular phase within healthy, non-smoking, normal-weight, proven normally ovulatory, premenopausal women with normal-length menstrual cycles?
Summary Answer
Prospective 1-year data from 53 premenopausal women with two proven normal-length (21-36 days) and normally ovulatory (≥10 days luteal) menstrual cycles upon enrollment showed that, despite 29% of all cycles having incident ovulatory disturbances, within-woman follicular phase length variances were significantly greater than luteal phase length variances.
What Is Known Already
Many studies report menstrual cycle variability, yet few describe variability in follicular and luteal phase lengths. Luteal lengths are assumed 'fixed' at 13-14 days. Most studies have described follicular and luteal phase variability between-women.
Study Design, Size, Duration
This study was a prospective, 1-year, observational cohort study of relative follicular and luteal phase variability both between and within community-dwelling women with two documented normal-length (21-36 days) and normally ovulatory (≥10 days luteal phase) menstrual cycles prior to enrollment. Eighty-one women enrolled in the study and 66 women completed the 1-year study. This study analyzed data from 53 women with complete data for ≥8 cycles (mean 13).
Participants/Materials, Setting, Methods
Participants were healthy, non-smoking, of normal BMI, ages 21-41 with two documented normal-length (21-36 days) and normally ovulatory (≥10 days luteal phase) menstrual cycles prior to enrollment. Participants recorded first morning temperature, exercise durations, and menstrual cycle/life experiences daily in the Menstrual Cycle Diary. We analyzed 694 cycles utilizing a twice-validated least-squares Quantitative Basal Temperature method to determine follicular and luteal phase lengths. Statistical analysis compared relative follicular and luteal phase variance in ovulatory cycles both between-women and within-woman. Normal-length cycles with short luteal phases or anovulation were considered to have subclinical ovulatory disturbances (SOD).
Main Results and the Role of Chance: The 1-year overall 53-woman, 676 ovulatory cycle variances for menstrual cycle, follicular, and luteal phase lengths were 10.3, 11.2, and 4.3 days, respectively. Median variances within-woman for cycle, follicular, and luteal lengths were 3.1, 5.2, and 3.0 days, respectively. Menstrual cycles were largely of normal lengths (98%) with an important prevalence of Sod: 55% of women experienced >1 short luteal phase (<10 days) and 17% experienced at least one anovulatory cycle. Within-woman follicular phase length variances were greater than luteal phase length variances (P < 0.001). However, follicular (P = 0.008) and luteal phase length (P = 0.001) variances, without differences in cycle lengths, were greater in women experiencing any anovulatory cycles (n = 8) than in women with entirely normally ovulatory cycles (n = 6).
Limitations, Reasons for Caution
Limitations of this study include the relatively small cohort, that most women were White, initially had a normal BMI, and the original cohort required two normal-length and normally ovulatory menstrual cycles before enrollment. Thus, this cohort's data underestimated population menstrual cycle phase variances and the prevalence of SOD.
Wider Implications of the Findings
Our results reinforce previous findings that the follicular phase is more variable than the luteal phase in premenopausal women with normal-length and ovulatory menstrual cycles. However, our study adds to the growing body of evidence that the luteal phase is not predictably 13-14 days long. STUDY FUNDING/COMPETING INTEREST(S): This medical education project of the University of British Columbia was funded by donations to the Centre for Menstrual Cycle and Ovulation Research. The authors do not have any conflicts of interest to disclose.
PMID 39320898 39320898 DOI 10.1093/humrep/deae215 10.1093/humrep/deae215 Henry et al. 2024, Henry 2024
Cite this article
Henry, S., Shirin, S., Goshtasebi, A., & Prior, J. C. (2024). Prospective 1-year assessment of within-woman variability of follicular and luteal phase lengths in healthy women prescreened to have normal menstrual cycle and luteal phase lengths. Human reproduction (Oxford, England), 39(11), 2565-2574. https://doi.org/10.1093/humrep/deae215
Henry S, Shirin S, Goshtasebi A, Prior JC. Prospective 1-year assessment of within-woman variability of follicular and luteal phase lengths in healthy women prescreened to have normal menstrual cycle and luteal phase lengths. Hum Reprod. 2024;39(11):2565-2574. doi:10.1093/humrep/deae215
Henry, S., et al. "Prospective 1-year assessment of within-woman variability of follicular and luteal phase lengths in healthy women prescreened to have normal menstrual cycle and luteal phase lengths." Human reproduction (Oxford, England), vol. 39, no. 11, 2024, pp. 2565-2574.
Johnson KA et al., 2016·Pharmacoepidemiol Drug Saf·
Open Access
The purpose of this study is to characterize the patterns of medication intake in healthy, reproductive-age women not using hormonal contraception. Two hundered fifty-nine healthy, premenopausal women (18-44 years of age) enrolled in the BioCycle Study (2005-2007) were followed over two menstrual cycles. Women were excluded if they were currently using oral contraceptives or other chronic medications. Over-the-counter and prescription medication use among participants was evaluated daily throughout the study via a diary assessing type of medication, dosage, units, and frequency. Medications were categorized as allergy, antibiotics, central nervous system (CNS), cold and cough, gastrointestinal, musculoskeletal, and pain medication based on primary active ingredient. Medication use within each category was assessed across standardized 28-day cycles to evaluate differences in use across cycle phases (i.e., early, middle, and late). Medication use was reported by 73% of participants. The most and least frequently used medications, respectively, were pain (69%) and musculoskeletal medications (1%). Pain, CNS, and antibiotic medication use varied significantly across the cycle, with pain and CNS medication more frequently reported during menses and antibiotics more frequently during the luteal phase. Allergy, cold and cough, gastrointestinal, and musculoskeletal medication use did not vary across the cycle. Patterns of medication use among reproductive age women vary across the menstrual cycle for certain types of medications, particularly in pain (e.g., Ibuprofen), antibiotics (e,g, Amoxicillin), and CNS (e.g., Adderall) medications. Future studies involving use of these types of medication in premenopausal women may need to consider the relationship of their use to the menstrual cycle.
Malliou-Becher MN et al., 2026·Human reproduction (Oxford, England)
What are the variations in ovulation time and menstrual cycle characteristics among and within various individuals over the course of 12 menstrual cycles? There are considerable variations in both cycle length and ovulation time, with pronounced intra-individual variability over a 12-cycle observation period. Although it is commonly believed that healthy women have regular cycles with a predictable mid-cycle ovulation, more recent research shows a significant variation in cycle length and ovulation time. Previous studies have focused only on cycle length, often excluding cycles outside the 25-35-day range, thus limiting the understanding of natural variation; they have also lacked precise ovulation diagnostics or included small sample sizes, making it difficult to capture the full scope of cycle and ovulation variability. Similarly, a recent big data study, while valuable, was limited by a self-selected group and the absence of accurate ovulation diagnostics, reducing its generalizability. STUDY DESIGN, SIZE, This study was designed as a prospective long-term observational study, which involved collecting data from 1923 women with a total of 43 999 menstrual cycles from January 1985 to July 2019. After fulfilling the inclusion criteria, the main group consisted of 1051 women, all of whom contributed data for 12 cycles (12 612 cycles), including 420 conception cycles. PARTICIPANTS/MATERIALS, SETTING, Participants in the study were between 18 and 44 years of age at study entry and did not take any reproductive hormones. Women who were postpartum, breastfeeding, amenorrheic, or within a 3-month period after stopping hormonal contraception were excluded. Participants agreed to keep cycle records according to the symptothermal method, 'Sensiplan'. Ovulation time was determined using an evidence-based algorithm based on evaluating cervical mucus patterns and basal body temperature shifts, with ovulation time defined as the day before the temperature rise. Data analysis was descriptive, using absolute and relative frequencies, standard deviation, percentiles, and ranges. Age dependency was assessed using unpaired sample t-tests and one-way ANOVA. Linear regression was used to assess long-term trends. MAIN In 62.4% of women, cycle lengths varied by 1 week or more within 12 cycles. Accordingly, the time of ovulation varied by 1 week or more within 12 cycles in 54.8% of women, with 96.5% experiencing fluctuations of 4 days or more over the 12 months. The median spontaneous cycle length was 28 days, with a mean of 29.66 days (SD = 7.55). Only 52.7% of women consistently had cycle lengths between 23 and 35 days across all 12 cycles. Ovulation occurred most frequently between Days 12 and 16, with almost half of conceptions (45.7%) occurring after Day 16. A one-way analysis of variance revealed a significant reduction in mean cycle length with increasing age (P < 0.001), showing the shortest median cycle length of 27 days being in women aged 40-44 years. Age also impacted ovulation time, with women aged 35-39 years showing more stable ovulation patterns compared to younger women. Over the 34-year study period, average cycle length increased slightly but significantly (β = 0.0161, P = 0.0306), corresponding to approximately half a day. Intra-individual variability also showed a slight, but non-significant, upward trend (β = 0.0262, P = 0.2173). LIMITATIONS, Comorbidities such as hyperprolactinemia, obesity, and PCOS were not systematically excluded. However, by including only women with at least 12 cycles, the study largely avoided severe hormonal disorders. This study highlights the considerable individual variation of ovulation time and cycle length over 12 menstrual cycles. These findings contribute to a better understanding of fertility awareness, and highlight the implications for family planning and reproductive health management. STUDY FUNDING/COMPETING INTEREST(S): The authors declare no conflicts of interest. No funding was provided. N/A.
Are prospectively assessed dietary factors, including overall diet quality, macronutrients and micronutrients, associated with luteal phase deficiency (LPD) in healthy reproductive aged women with regular menstrual cycles? Mediterranean Diet Score (MDS), fiber and isoflavone intake were positively associated with LPD while selenium was negatively associated with LPD after adjusting for age, percentage body fat and total energy intake. LPD may increase the risk of infertility and early miscarriage. Prior research has shown positive associations between LPD and low energy availability, either through high dietary restraint alone or in conjunction with high energy expenditure via exercise, but few studies with adequate sample sizes have been conducted investigating dietary factors and LPD among healthy, eumenorrheic women. STUDY DESIGN, SIZE, The BioCycle Study (2005-2007) prospectively enrolled 259 women from Western New York state, USA, and followed them for one (n = 9) or two (n = 250) menstrual cycles. PARTICIPANTS/MATERIALS, SETTING, Women aged 18-44 years, with self-reported BMI between 18 and 35 kg/m(2) and cycle lengths between 21 and 35 days, were included in the study. Participants completed baseline questionnaires, four 24-h dietary recalls per cycle and daily diaries capturing vigorous exercise, perceived stress and sleep; they also provided up to eight fasting serum samples during clinic visits timed to specific phases of the menstrual cycle using a fertility monitor. Cycles were included for this analysis if the peak serum luteal progesterone was >1 ng/ml and a urine or serum LH surge was detected. Associations between prospectively assessed diet quality, macronutrients and micronutrients and LPD (defined as luteal duration <10 days) were evaluated using generalized linear models adjusting for age, percentage body fat and total energy intake. MAIN LPD occurred in 41 (8.9%) of the 463 cycles from 246 women in the final analysis. After adjusting for age, percentage body fat and total energy intake, LPD was positively associated with MDS, adjusted odds ratio (aOR): 1.70 (95% confidence interval [CI]: 1.17, 2.48), P = 0.01. In separate macro- and micronutrient adjusted models, increased fiber and isoflavone intake showed modest positive associations with fiber (per g), aOR: 1.10 (95% CI: 0.99, 1.23), P = 0.07; and isoflavones (per 10 mg), aOR: 1.38 (95% CI: 0.99, 1.92), P = 0.06. In contrast, selenium (per 10 mcg) was inversely associated with LPD, aOR: 0.80 (95% CI: 0.65, 0.97), P = 0.03. Additional adjustments for relevant lifestyle factors including vigorous exercise, perceived stress and sleep did not appreciably alter estimates. LIMITATIONS, The number of LPD cycles was limited, and thus these findings are exploratory. We relied on participant self-report of their medical history to apply exclusion criteria; it is possible that we admitted to the study women with a gynecologic or medical disease who were unaware of their diagnosis. Our study suggests that diet quality may be associated with LPD among healthy eumenorrheic women. As LPD may contribute to infertility and early miscarriage, further research is warranted to elucidate how dietary factors, such as MDS, may influence LPD. The inverse association we found with selenium is supported by previous research and deserves further investigation to determine whether this finding has pathophysiologic and therapeutic implications. This work was supported by the Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health. No competing interests declared.
The period in each menstrual cycle during which sexual intercourse can result in conception is called the "fertile window". Although the fertile window closes on the day of ovulation, little is known about the moment it opens. We defined the first day of normal sperm-mucus interaction as the opening of the fertile window. We hypothesized that length of the fertile window varies between couples and that the number of days the fertile window is "open" is related to the time to spontaneous conception. METHODS Serial post-coital tests and sperm-mucus penetration tests were performed to detect the first normal sperm-mucus interaction day. Ovulation was confirmed by serial ultrasound. Using Cox' regression analysis, we determined whether the fertile window length was associated with time to ongoing pregnancy. This association was expressed in fecundability ratios (FR). RESULTS The fertile window length was determined in 410 subfertile couples. The fertile window length varied among couples from <1 to >5 days. The FR increased with increasing fertile window length and varied between 0.11 (95% CI: 0.03-0.45) for a fertile window of 1 day, to 2.4 (95% CI: 1.1-5.2) for a fertile window of 5 days or more. CONCLUSIONS The longer the fertile window in subfertile couples, the higher is the probability of spontaneously conceiving an ongoing pregnancy.