The methods of Natural Family Planning are based on scientific research about women's menstrual cycles, the signs of female fertility which are related to the event of ovulation, and the "fertile window" which takes into account how long a man's sperm can live in a woman's body.

Over a century ago, scientists discovered cyclic changes in a woman's cervical fluid (or "mucus") and their relation to ovulation. In the 1920s, scientists identified the temperature rise ("basal body temperature" or BBT) that signals ovulation. But it wasn't until the 1950s that scientists developed programs to teach others how to observe and interpret these fertility signs. Today, ongoing research continues to refine the methods of NFP. Here we present both classic and current NFP research.

Learn more about the following topics

NFP Science Resources

NFP Fact Checker

This one hour and fifteen-minute audio file is from the 2013 annual conference of the National Association of Catholic Family Life Directors (NACFLM). The panel discusses the research behind such topics as: NFP effectiveness rates, the truth (or myth) behind the "less than 5% divorce rate" of NFP users; and other commonly misunderstood "facts" about NFP.

Panelists are Richard Fehring, Ph.D., RN, NFP Institute, Marquette University, College of Nursing and Michael Manhart, Ph.D., Couple to Couple League. The MC is Theresa Notare, Ph.D., Assistant Director, NFP Program, Secretariat of Laity, Marriage, Family Life, and Youth, USCCB. 
Part One | Part Two | Part Three | Part Four | Part Five

NFP Fact Checker PowerPoint Slides
Part I | Part II Please view Dr. Fehring and Dr. Manhart's slides that accompany the talks.

Note: The audio files are here for your use with the permission of Catholic Seminars. If you would like to purchase the files and view other files available from the 2013 NACFLM conference, see:

Research Articles
"Natural Family Planning: A Review," Hanna Klaus, MD
This article provides a review of the classic scientific research behind the various methods of NFP.

The Methods of Natural Family Planning

Human Reproduction

Psycho-Social Studies