Mucus observations in the fertile window: a better predictor of conception than timing of intercourse

Bigelow JL; Dunson DB; Ecochard R; Gnoth C; Colombo B; Stanford JB

doi:10.1093/humrep/deh173

Fertility Awareness · Biomarkers

Mucus observations in the fertile window: a better predictor of conception than timing of intercourse

Bigelow JL, Dunson DB, Ecochard R, Gnoth C, Colombo B, Stanford JB

Published April 2004 Human Reproduction (Oxford, England), 19(4), 889-892

DOI 10.1093/humrep/deh173 PMID 14990542

RRM Academy Synopsis

Mucus in the fertile window predicts conception better than timing

A prospective cohort of 782 European women who tracked their cycles daily found that mucus quality predicted conception better than timing relative to ovulation. Pregnancy probability rose with each step of a daily 1 to 4 mucus score. Day-by-day probabilities varied little across the fertile interval once mucus was included.

Study at a glance, prospective cohort: Mucus quality predicted conception better than timing of intercourse — Study at a glance, prospective cohort of 782 European women: Mucus quality predicted conception better than timing of intercourse. Source: Bigelow JL et al., 2004, PMID 14990542.

Key Findings

Mucus score and pregnancy probability rose together once timing and frequency of intercourse were accounted for. The posterior probability of no mucus effect was below 0.01.
The posterior probability that pregnancy probability increased was 0.95 from mucus score 1 to 2, 0.97 from 2 to 3, and above 0.99 from 3 to 4.
Pregnancy probability was lowest with intercourse 5 days before ovulation and highest 3 days before, a gap of 0.06 to 0.14 that varied with mucus quality.
Pregnancy probability was 0.1 to 0.18 higher at mucus score 4 than at score 1, generally a larger difference than between intercourse 3 days and 5 days before ovulation.
With type 4 mucus, the pregnancy probability for intercourse on any day of the 6-day window was above 0.17. On days with no secretions (score 1), it did not exceed 0.13.

Interpretation

The European Study of Daily Fecundability enrolled 782 women aged 18 to 40 at seven centers that teach natural family planning. The women were experienced in the methods, and neither partner had a history of fertility problems. Each woman recorded basal body temperature, cervical mucus and intercourse daily. Researchers dated ovulation from the temperature record. A Bayesian model then estimated pregnancy probabilities for each day across 1473 cycles with 353 pregnancies. The authors conclude that days with optimal mucus quality are the best days for intercourse to maximize the likelihood of conception.

RRM Context

Mucus observation is the central daily sign in the Creighton Model and the Billings Ovulation Method, and NaProTechnology charting records it as well. The paper links those observations to the chance of conception on a given day. Restorative reproductive medicine reads a cycle chart as information about ovulation, so a woman's own daily observations join the record that couples and clinicians use together.

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

Abstract

Background

Intercourse results in a pregnancy essentially only if it occurs during the 6-day fertile interval ending on the day of ovulation. The strong association between timing of intercourse within this interval and the probability of conception typically is attributed to limited sperm and egg life times.

Methods

A total of 782 women recruited from natural family planning centres in Europe contributed prospective data on 7288 menstrual cycles. Daily records of intercourse, basal body temperature and vaginal discharge of cervical mucus were collected. Probabilities of conception were estimated according to the timing of intercourse relative to ovulation and a 1-4 score of mucus quality.

Results

There was a strong increasing trend in the day-specific probabilities of pregnancy with increases in the mucus score. Adjusting for the mucus score, the day-specific probabilities had limited variability across the fertile interval.

Conclusions

Changes in mucus quality across the fertile interval predict the observed pattern in the day-specific probabilities of conception. To maximize the likelihood of conception, intercourse should occur on days with optimal mucus quality, as observed in vaginal discharge, regardless of the exact timing relative to ovulation.

Topics

Fertility Awareness › Biomarkers › Cervical Mucus · Menstrual Cycle › Cycle Biomarkers › Cervical Mucus

Jamie L Bigelow, Bernardo Colombo, David B Dunson, René Ecochard, Joseph B Stanford

J Bigelow, B Colombo, Dave Dunson, D Dunson, R Ecochard, Joe Stanford, Joey Stanford, J Stanford

PMID 14990542 14990542 DOI 10.1093/humrep/deh173 10.1093/humrep/deh173 Bigelow et al. 2004, Bigelow 2004

Keywords

Adult, Cervix Mucus/physiology, Cohort Studies, Coitus, Europe, Female, Fertility/physiology, Fertilization, Humans, Medical Records, Natural Family Planning Methods/standards, Pregnancy, Probability, Prospective Studies, Time Factors

Mucus observations in the fertile window: a better predictor of conception than timing of intercourse

Mucus in the fertile window predicts conception better than timing

Key Findings

Interpretation

RRM Context

Abstract

Topics

By this author

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Keywords