Hilgers, T. W., Prebil, A. M., Hilgers, S. K., & Daly, K. D. (1980). The Occurrence of Ovulation at the Midcycle.
Hilgers TW, Prebil AM, Hilgers SK, Daly KD. The Occurrence of Ovulation at the Midcycle. 1980.
Hilgers, T. W., et al. The Occurrence of Ovulation at the Midcycle. 1980.
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Saint John's Mercy Medical Center
Pope Paul VI Institute for the Study of Human Reproduction, Omaha, Nebraska.027jqx654
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RRM Academy Synopsis
Ovulation on day 14 was uncommon across 66 ovulatory cycles
Ovulation fell on day 14 in only about 14 out of 100 cycles in a small 1980 study. It followed 24 women ages 20 to 38 chosen for essentially normal characteristics. Across their 66 ovulatory cycles, the estimated ovulation day spread over 17 days.
Key Findings
The 66 ovulatory cycles came from 24 women ages 20 to 38. Cycle length ranged from 23 to 38 days, with a mean of 28.8 days.
The estimated time of ovulation fell on day 14 in 13.6% of cycles. It fell on the exact midcycle day in 13.8% of the 65 cycles with known length.
In these cycles, the estimated time of ovulation covered a 17-day range around day 14. The highest cluster, within 2 days either side of day 15, held 62.1%.
Midcycle coincided with day 14 in 11 of 65 cycles (16.9%).
The estimated time of ovulation came after day 14 in 65.2% of cycles and after the midcycle in 72.4%.
Interpretation
The study is a small observational report on women chosen for essentially normal characteristics, so the results describe similar women. The authors estimated ovulation from hormone measurements in daily blood samples. They counted only cycles they judged ovulatory. The report analyzes the timing of estimated ovulation. The true midcycle is known only after a cycle ends. In this series, the authors found the range too wide to determine ovulation by counting days. They say frequent ovulation after day 14 tends to speak for its normalcy.
RRM Context
The authors report a wider range of estimated ovulation days around day 14 than around the Peak symptom or the basal body temperature endpoints. Charting methods such as the ovulation method of NFP follow each cycle's own signs, including mucus and temperature. Day counting follows the calendar alone. The Creighton University NFP research center produced the paper.
Our editorial summary of this paper, not the article's abstract.
Abstract
It is commonplace for gynecologists to refer to "midcycle" ovulation of women. This concept has often led to the routine diagnosis of ovulatory status on day 14 of what is expected to be a 28-day menstrual cycle. For example, the postcoital test in an infertile patient, or intercourse to achieve pregnancy in a normally fertile patient, is often timed around day 14 under the assumption that ovulation is occurring then. Advocates of natural family planning (NFP) have criticized the concept of "midcycle" ovulation, because their clinical experience suggests that the natural irregularity of menstrual-cycle length militates against ovulation's occurring with any great frequency on day 14. This report analyzes the relationship of day 14 and the actual midcycle of the menstrual cycle to each other and to indirect hormonal parameters that more directly estimate the time of ovulation.
Hilgers TW, 2020·Linacre Q·Free full text on PubMed Central
This study reports on 632 cycles from 105 women who were using the CREIGHTON MODEL FertilityCare™ System to avoid pregnancy and had either a serious reason to avoid pregnancy or some degree of a lack of confidence. A progesterone level was drawn on the third day after the Peak Day as they were charting, and if the progesterone level was 2.3 ng/mL or greater, then ovulation was determined to have passed. If the level was greater than 3.0 ng/mL, this indicated that an absolute period of infertility had begun. In these cases, no pregnancies were observed. In the 27 cycles in which a specific follow-up relative to pregnancy could not be definitively determined, the progesterone levels in all cases were 2.3 ng/mL or greater with 23 of the 27 cycles being 3.1 ng/mL or greater. It is highly unlikely that any of those became pregnant as well. These cycles were collected over thirteen years (2004-2016). Two case presentations are also a part of this article of two families in which the couples had very serious reasons to avoid pregnancy. In these two couples, each of the women was multi-gravid and had no evidence of subfertility or infertility. They used the family planning progesterone level (the Peak Day +3 progesterone level) for a total of 167 cycles over a number of years successfully without a subsequent pregnancy.
This article presents a thirteen-year effort to evaluate the serum progesterone level on the third day after the Peak Day as observed by women charting the CREIGHTON MODEL FertilityCare™ System. It is known that the Peak Day is associated with ovulation, and if the progesterone reaches a certain level, then an absolute period of infertility should follow. In fact, this is what this study reflects.
Chang CP et al., 2020·Paediatr Perinat Epidemiol·Free full text on PubMed Central
Previous research has demonstrated that women instructed in fertility awareness methods can identify the Peak Day of cervical mucus discharge for each menstrual cycle, and the Peak Day has high agreement with other indicators of the day of ovulation. However, previous studies enrolled experienced users of fertility awareness methods or were not fully blinded. To assess the agreement between cervical mucus Peak Day identified by fertile women without prior experience on assessing cervical mucus discharge with the estimated day of ovulation (1 day after urine luteinising hormone surge). This study is a secondary analysis of data from a randomised trial of the Creighton Model FertilityCare(TM) System (CrM), conducted 2003-2006, for women trying to conceive. Women who had no prior experience tracking cervical mucus recorded vulvar observations daily using a standardised assessment of mucus characteristics for up to seven menstrual cycles. Four approaches were used to identify the Peak Day. The referent day was defined as one day after the first identified day of luteinising hormone (LH) surge in the urine, assessed blindly. The percentage of agreement between the Peak Day and the referent day of ovulation was calculated. Fifty-seven women with 187 complete cycles were included. A Peak Day was identified in 117 (63%) cycles by women, 185 (99%) cycles by experts, and 187 (100%) by computer algorithm. The woman-picked Peak Day was the same as the referent day in 25% of 117 cycles, within ±1 day in 58% of cycles, ±2 days in 84%, ±3 days in 87%, and ±4 days in 92%. The ±1 day and ± 4 days' agreement was 50% and 90% for the expert-picked and 47% and 87% for the computer-picked Peak Day, respectively. Women's daily tracking of cervical mucus is a low-cost alternative for identifying the estimated day of ovulation.
Daly KD et al., 2019·Linacre Q·Free full text on PubMed Central
A special course on Marriage, the Family and Human Sexuality was established at Kenrick-Glennon Seminary in St. Louis so as to assist the seminarians in their better understanding of the Church's teaching relative to natural methods of family planning and women's health care. This article compares the response at the beginning of this three-credit semester course to the same seven-item questionnaire given at the conclusion of the course. The preand postcourse scores were calculated for each of the questions. The scores obtained after the course were all significantly higher than they were before the course with p values ranging from 0.01 to <0.0001. Four of the items showed marked improvement including an understanding of the church's teaching related to natural methods, current methods of natural family planning, the impact of a natural method on a couple's marriage, and also the impact of a natural method on family life. Statistically significant improvement was also seen in their understanding of the topic of natural family planning and the Creighton Model System and its relevance toward the seminarian's vocation, the use of the methods to either achieve or avoid pregnancy, and how contraception and abortion are linked. In these last three items, the level of statistical significance was quite high, although not as high as the other four items. There were 104 seminarians over an eight-year period of time, who provided answers to these questions, both before and after the course. This course was modeled after a course that was initiated at the Pope Paul VI Institute for the Study of Human Reproduction, which was for priests, seminarians, and Catholic leaders, titled Love & Life Unlimited. NONTECHNICAL This is an evaluation of a ten-point, seven-question questionnaire that was utilized at the beginning of a course at Kenrick Seminary in Marriage, Sexuality, Creighton Model and NaProTECHNOLOGY. The same questionnaire was given to the students at the beginning of the course and then two to three months later at the conclusion of the three-credit course. The results show that there is a significant improvement in the seminarians' knowledge and general attitude about natural methods of family planning and suggests that such courses would be beneficial to establish in seminaries throughout the country.
Progesterone support in pregnancy has been in use for over 60 years, having received its start in the 1940s. Its initial use was in patients who had habitual spontaneous abortion caused by luteal phase deficiency. More recently, the administration of progesterone later in pregnancy has been considered to be justified because of an observed decrease in circulating progesterone with the onset of labor, an association of premature labor with decreased progesterone concentrations, and the observation that progesterone has a tocolytic effect. A considerable boost to the use of progestational agents to reduce preterm delivery was received with the publication of two papers which showed a significant reduction in preterm delivery rates with the prophylactic administration of either progesterone or 17-a hydroxyprogesterone caproate. Recently it has been shown, however, that its use is not universal. This may be related to the significant late sequelae that were documented following the in utero exposure of the fetus to the potent steroid diethylstilbestrol (DES) and that this bad experience cast “a long shadow,” In spite of this, the use of progesterone, at least in early pregnancy, is widespread in the various artificial reproductive programs and is growing in its use as an agent to reduce prematurity. Over the years, there has been an extraordinary amount of confusion related to the use of progesterone support in pregnancy. The Food & Drug Administration (FDA) created some of this confusion. In various labeling of progesterone products by the FDA, one of the contraindications to the use of oral progesterone is listed as “known or suspected pregnancy.” And, yet, no such contraindication is identified for the use of progesterone gel. In fact, progesterone gel is indicated for progesterone supplementation or replacement as a part of an assisted reproductive technology (ART) treatment program for infertile women with a progesterone deficiency. To make this even more confusing, oral progesterone, while it was contraindicated in “known or suspected pregnancy,” its official labeling stated that it “should be used during pregnancy only if indicated (see contraindications).” Also, up until very recently, there was a dire “warning” contained in the labeling for USP progesterone injection in sesame seed oil regarding an increased possibility of birth defects. An analysis of the fetal safety of isomolecular progesterone (Pregn-4-ene-3,20-dione) administration during the course of 1,310 pregnancies over a 35-year period of time (1979-2014) was undertaken to address this confusion.
Fehring RJ et al., 2006·J Obstet Gynecol Neonatal Nurs·Free to read
To determine variability in the phases of the menstrual cycle among healthy, regularly cycling women.
A prospective descriptive study of a new data set with biological markers to estimate parameters of the menstrual cycles. 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. 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). 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. Among regularly cycling women, there is considerable normal variability in the phases of the menstrual cycle. The follicular phase contributes most to this variability.
Wilcox AJ et al., 2000·BMJ·Free full text on PubMed Central
To provide specific estimates of the likely occurrence of the six fertile days (the "fertile window") during the menstrual cycle.
Prospective cohort study. 221 healthy women who were planning a pregnancy. The timing of ovulation in 696 menstrual cycles, estimated using urinary metabolites of oestrogen and progesterone. The fertile window occurred during a broad range of days in the menstrual cycle. On every day between days 6 and 21, women had at minimum a 10% probability of being in their fertile window. Women cannot predict a sporadic late ovulation; 4-6% of women whose cycles had not yet resumed were potentially fertile in the fifth week of their cycle. In only about 30% of women is the fertile window entirely within the days of the menstrual cycle identified by clinical guidelines-that is, between days 10 and 17. Most women reach their fertile window earlier and others much later. Women should be advised that the timing of their fertile window can be highly unpredictable, even if their cycles are usually regular.
To improve prediction of ovulation in normal cycles. Collection of women's characteristics and their menstrual cycles. Monitoring and analysis of time relationships between several indicators of ovulation: transvaginal ultrasonography, cervical mucus, basal body temperature, urinary luteinising hormone, and ratio of urinary oestrogen to progesterone metabolites. Each of eight natural family planning clinics was to study 12 women for at least three cycles. One hundred and seven normally fertile and cycling women aged 18 to 45. Daily measurements of urinary luteinising hormone, follicle stimulating hormone, oestrone-3-glucuronide and pregnanediol-3alpha-glucuronide. Basal body temperature recording and cervical mucus checking. Transvaginal ultrasound examination of the ovaries. Delays between the expected day of ovulation according to the luteinising hormone peak or to ultrasound evidence and the expected days according to the other indices of ovulation. Ultrasonography was able to show evidence of ovulation in 283 out of 326 cycles. The average time lag between luteinising hormone peak and ultrasound evidence was less than one day (+0.46) but premature and late luteinising hormone-expected date of ovulation were observed in nearly 10% and 23% of cycles, respectively. Basal body temperature rise was observed in 98% of cycles. Cervical mucus peak symptom, rapid drop in the ratio of urinary metabolites, and luteinising hormone initial rise were all close to ultrasonographic evidence in more than 72% of cycles. For accuracy and practical reasons, the cervical mucus peak symptom, the ratio of urinary metabolites and luteinising hormone initial rise might be better indices of ovulation than the luteinising hormone peak.
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.
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