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NFP Science


The methods of Natural Family Planning (NFP) are based on scientific research about the fertility of men and women. NFP makes use of specific information about the women's menstrual cycle and the signs of female fertility, which are related to the event of ovulation (when the egg is released from the ovary). NFP also pinpoints the "fertile window" which takes into account how long a man's sperm can live in a woman's body when the woman is fertile.

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. It wasn't until the 1950s that scientists developed guidelines to teach men and women how to observe and interpret the signs of fertility. Today, research continues to refine the methods of NFP.

Learn more . . .
Human Fertility--What Biology Demonstrates
Cervical Mucus Method
Sympto-Thermal Method
Sympto-Hormonal Method
Other Fertility Awareness Based Methods


NFP Science Resources

Current Medical Research
This biannual publication provides reviews of research on the methods of NFP and related topics.

NFP Education for Healthcare Professionals

NFP Science PowerPoint Presentations

NFP Science and Methodology Videos
Scientific Basis of NFP Methods (provided by FACTS)
Overview of the NFP Methods (provided by FACTS)
NFP Effectiveness (provided by FACTS)
Achievig Pregnancy with NFP (provided by FACTS)

NFP Science Bibliography
This bibliography provides a list of classic and current NFP research.
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.

Richard Fehring, PhD, RN, NFP Institute, Marquette University, College of Nursing and
Michael Manhart, PhD, Couple to Couple League.
Theresa Notare, PhD, 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
View the slides that accompany the above presentation.
Part I;     Part II

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:



The Methods of Natural Family Planning

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

Basal Body Temperature Method

Cervical Mucus Method 

Sympto-Thermal Method

Sympto-Hormonal Method


Human Reproduction

The Menstrual Cycle

Breastfeeding and NFP

Topics in Human Fertility and NFP

Psycho-Social Studies

Human Behavior, NFP and the Couple Relationship 


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