Ovulation Prevalence in Women with Spontaneous Normal-Length Menstrual Cycles - A  Population-Based Cohort from HUNT3, Norway

Jerilynn C Prior; Marit Naess; Arnulf Langhammer; Siri Forsmo

doi:10.1371/journal.pone.0134473

Menstrual Cycle · Cycle Physiology

Ovulation Prevalence in Women with Spontaneous Normal-Length Menstrual Cycles - A Population-Based Cohort from HUNT3, Norway

Prior JC, Naess M, Langhammer A, Forsmo S

Published August 21, 2015 PloS One, 10(8), e0134473

DOI 10.1371/journal.pone.0134473 PMID 26291617 PMC PMC4546331

RRM Academy Synopsis

Over a Third of Regular Menstrual Cycles Showed No Sign of Ovulation

Over a third of women with regular, normal-length cycles showed no sign of ovulation in the cycle studied. This 2015 Norwegian cross-sectional study took one blood progesterone reading from each of 1,545 women in the presumed luteal phase. In all, 36.7% fell below the study's ovulation cutoff.

Key Findings

The main cohort held 3,168 women with regular, normal-length cycles; 1,545 of them gave a blood sample in the presumed luteal phase.
Of those 1,545 women, 978 (63.3%) had an ovulatory cycle and 567 (36.7%) were anovulatory, meaning no sign of ovulation.
Among the 1,545 women, those with and without ovulation did not differ in age, BMI, menarche age, smoking, activity, obesity or self-reported health. Parity differed slightly (96.7% vs. 94.5%, P = 0.04).
In the adjusted model, the lowest and highest estradiol categories predicted anovulation. Odds ratios for ovulation were 0.29 (95% CI 0.11 to 0.81) and 0.18 (95% CI 0.08 to 0.39).
With the strictest of four progesterone cutoffs, 45% of the 1,545 women counted as ovulatory. With the most lenient cutoff, 84% did.

Interpretation

The study is a cross-sectional survey: each woman contributed one sample from one cycle. Ovulation was inferred from a progesterone level, an indirect marker. The authors say it has not been validated against direct visualization of an egg leaving the ovary or serial ultrasound. Four of five experts the authors asked recommended the cutoff. Participants averaged early 40s, were mostly white, and 51.9% of invited women under 50 took part. One sample per woman cannot show whether the same women miss ovulation repeatedly. The authors read the similarity between the two groups as suggesting sporadic anovulation.

RRM Context

Restorative reproductive medicine treats the ovulatory cycle as a vital sign whose quality deserves measurement. This paper gives population data for that view: regular timing alone left over a third of sampled cycles without a progesterone rise. The authors name direct visualization of an egg leaving the ovary as the gold standard for documenting ovulation. Cycle charting informs evaluation across many cycles. A single-day sample cannot do that.

Our editorial summary of this paper, not the article's abstract.

Abstract

Background

Ovulatory menstrual cycles are essential for women's fertility and needed to prevent bone loss. There is a medical/cultural expectation that clinically normal menstrual cycles are inevitably ovulatory. Currently within the general population it is unknown the proportion of regular, normal-length menstrual cycles that are ovulatory. Thus, the objective of this study was to determine the population point prevalence of ovulation in premenopausal, normally menstruating women. The null hypothesis was that such cycles are ovulatory.

Methods

This is a single-cycle, cross-sectional, population-based study-a sub-study of the HUNT3 health study in the semi-rural county (Nord Trøndelag) in mid-Norway. Participants included >3,700 spontaneously (no hormonal contraception) menstruating women, primarily Caucasian, ages 20-49.9 from that county. Participation rate was 51.9%. All reported the date previous flow started. A single, random serum progesterone level was considered ovulatory if ≥9.54 nmol/L on cycle days 14 to -3 days before usual cycle length (CL).

Results

Ovulation was assessed in 3,168 women mean age 41.7 (interquartile range, [IQR] 36.8 to 45.5), cycle length 28 days (d) (IQR 28 to 28) and body mass index (BMI) 26.3 kg/m2 (95% CI 26.1 to 26.4). Parity was 95.6%, 30% smoked, 61.3% exercised regularly and 18% were obese. 1,545 women with a serum progesterone level on cycle days 14 to -3 were presumed to be in the luteal phase. Of these, 63.3% of women had an ovulatory cycle (n = 978) and 37% (n = 567) were anovulatory. Women with/ without ovulation did not differ in age, BMI, cycle day, menarche age, cigarette use, physical activity, % obesity or self-reported health. There were minimal differences in parity (96.7% vs. 94.5%, P = 0.04) and major differences in progesterone level (24.5 vs. 3.8 nmol/L, P = 0.001).

Conclusion

Anovulation in a random population occurs in over a third of clinically normal menstrual cycles.

Topics

Menstrual Cycle › Cycle Physiology › Ovulation · Reproductive Endocrinology › Ovulation Physiology › Anovulation · Diagnostics › Hormone Testing › Serum Panels

Jerilynn C Prior, Marit Naess, Arnulf Langhammer, Siri Forsmo

J Prior, M Naess, A Langhammer, S Forsmo

PMID 26291617 26291617 DOI 10.1371/journal.pone.0134473 10.1371/journal.pone.0134473 Prior et al. 2015, Prior 2015

Keywords

Progesterone