Fecundability in relation to use of fertility awareness indicators in a North American preconception cohort study

We prospectively evaluated the association between fertility awareness indicators and fecundability among pregnancy planners. Use of fertility indicators to track the fertile window was associated with greater fecundability.

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Volume 112, Issue 5, Pages 892–899


Joseph Barney Stanford, M.S.P.H., M.D., Joseph Barney Stanford, Sydney Kaye Willis, M.S.P.H., Elizabeth Elliott Hatch, M.S., Ph.D., Kenneth Jay Rothman, Dr.P.H.b,, Lauren Anne Wise, M.Sc., Sc.D.



To quantify the frequency of use of selected fertility awareness indicators and to assess their influence on fecundability.


Web-based prospective cohort study.


Not applicable.


Female pregnancy planners, aged 21–45 years, attempting conception for ≤6 cycles at study entry.



Main Outcome Measure(s)

We ascertained time to pregnancy, in menstrual cycles, with bimonthly questionnaires. We estimated adjusted fecundability ratios (FRs) and confidence intervals (CIs) using proportional probabilities models, controlling for age, income, education, smoking, intercourse frequency, and other lifestyle and reproductive factors.


A total of 5,688 women were analyzed, with a mean age of 29.9 years and mean time trying of 2.1 cycles at baseline; 30% had ever been pregnant. At baseline, 75% were using one or more fertility indicators (counting days or charting menstrual cycles [71%], measuring basal body temperature [BBT, 21%], monitoring cervical fluid [39%], using urine LH tests [32%], or feeling for changes in position of the cervix [12%]). Women using any fertility indicator at baseline had higher subsequent fecundability (adjusted FR 1.25, 95% CI 1.16–1.35) than those not using any fertility indicators. For each individual indicator, adjusted FRs ranged from 1.28–1.36, where 1.00 would indicate no relation with fecundability. The adjusted FR for women using a combination of charting days, cervical fluid, and urine LH was 1.48 (95% CI 1.31–1.67) relative to women using no fertility indicators.


In a North American preconception cohort study, use of fertility indicators indicating the fertile window was common, and was associated with greater fecundability.

Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders.