Human sexuality is woven into the fabric of each man and woman. It carries within it the powers of love and life and is the human source of our most basic relationships as members of a family (see Love and Sexuality).

Striving to understand God's design of human fertility, reveals the marvelous intention of the Creator--to unite the two into one flesh where new life may worthily enter the world.

The methods of Natural Family Planning (NFP) exist because of God's design of man, woman, human sexuality and fertility. NFP methodology is based on scientific research about women's menstrual cycles, the signs of female fertility which are related to the event of ovulation (when a mature egg is released from an ovary in the woman's body), 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 About The Science and Methodology of NFP

Human Reproduction, How God Made Men and Women
Cervical Mucus Method
Sympto-Hormonal Method
Sympto-Thermal Method
Other Fertility-Appreciation Based Methods
NFP and Effectiveness

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

NFP Science PowerPoint Presentations

NFP Fact Checker--A Panel Discussion
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. Although produced in 2013, the content highlights principles that guide evidence-based review of NFP research.

Panelists are Richard Fehring, PhD, RN, NFP Institute, Marquette University, College of Nursing and Michael Manhart, PhD, Couple to Couple League. The MC is 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
Part I | Part II Please view Dr. Fehring and Dr. Manhart's slides that accompany the talks.

Select NFP Science Articles

(See also the NFP Science Bibliography for a list of foundational and current research.)

The content below represents the research of the authors. Links to external websites are provided solely for the user's convenience. Reference to these sites do not imply USCCB official endorsement.

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

The Methods of Natural Family Planning

Human Reproduction

Psycho-Social Studies


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