Influence of cycle variability and coital frequency on the risk of pregnancy

Markus J. Steiner, Irva Hertz-Picciotto, Elizabeth Raymond, James Trussell, Angie Wheeless, Victor Schoenbach

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Researchers have cautioned against generalizing results from contraceptive trials because these studies rely on self-selected participants meeting strict selection criteria who may differ from typical users. Using information collected on daily diaries, we reanalyzed data from the recently completed Reality® female condom clinical trial to evaluate factors that influence the probability of pregnancy. Noncompliant women, women with less variable menstrual cycles (17-43 days), and women engaging in intercourse frequently (≥11 acts per month) were more likely to conceive during this 6-month trial. The adjusted hazard ratios and 95% confidence intervals for these three covariates were 6.1 (2.0-18.7), 7.2 (1.0-54.3), and 2.0 (0.7-5.3), respectively. The strict selection criteria used in this study failed to recruit a homogeneous cohort with respect to factors that influence the risk of pregnancy. The overall pregnancy rate does not pertain to individual study participants, but rather represent average effects for a population with the particular mix of characteristics found in this study. In particular, we not only confirm the well known importance of compliance and the obvious role of frequency of intercourse, but also demonstrate that women with cycles outside the range of 17-43 days appear to be at a much lower risk of pregnancy. Copyright (C) 1999 Elsevier Science Inc.

Original languageEnglish (US)
Pages (from-to)137-143
Number of pages7
Issue number3
StatePublished - Sep 1999
Externally publishedYes


  • Coitus
  • Contraceptive behavior
  • Family planning
  • Female condoms
  • Female contraceptive devices
  • Menstrual cycle

ASJC Scopus subject areas

  • Medicine(all)
  • Obstetrics and Gynecology


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