Sympto-Thermal Methods provide information on the primary sign of fertility, cervical mucus and include basal body temperature readings as a support or double check to confirm the end of fertility.

Sympto-Thermal Methods (STM) emphasize the relationship between at least two of the primary signs of fertility (for most, this is the change in cervical mucus and the BBT). Whichever two primary signs first support each other, it is very important to make accurate observations, record them, identify the Peak Day of fertility correctly, and confirm the beginning of the infertile time.

STM education can include information on other signs of fertility such as: changes in the cervix, breast tenderness, mid-cycle back pain, etc. Variations in STM rules, charting two or more of the primary signs of fertility, as well as differences in chart symbols, exist among NFP methods.

To learn more about the STM, see the Introduction to NFP

For foundational STM research, see the NFP Science Bibliography.

Learn STM

Please note that each STM treats the teaching of the sensation, observation, and daily charting of cervical mucus differently as well as how to chart and interpret the Basal Body Temperature. In order to decide which STM is best for you, contact the NFP provider. To view the list of national NFP providers, see Learn NFP.


STM NFP Providers

Select Articles

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

Please be advised that 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.

Please be patient with us as we continue to develop this page. Send suggestions to


A Summary of the Fairfield Study
Frank J. Rice, Claude A. Lanctot, and Consuelo Garcia-Devesa
This article reports on an international study from1977 of the statistical evaluation of the Sympto-Thermal Method. The study conducted was of fertile women from five different countries to determine menstrual cycle length and pregnancy rates. They tested women using STM as compared to those using contraceptives.

Further Evolution of the Sympto-Thermal Methods
Josef Roetzer
This article describes the tested effectiveness of the Sympto-Thermal Method. It explains, in detail, how to chart a menstrual cycle with the different approaches to STM. In doing so, Dr. Roetzer examines the evolution of the Sympto-Thermal Method and the reliability gained in conception regulation.

Pathfinder: Wilhelm Hillebrand, First Teacher of the Sympto-Thermic Method
Rudolf f. Vollman
This article discusses the pioneering work in the Sympto-Thermal Method by Father Wilhelm Hillebrand, a parish priest in Germany in the 20th century.

Sympto-Thermal Methods of Natural Family Planning
Josef Roetzer
With today's pedagogical techniques, almost 100% of fertile women can recognize their menstrual cycle based on mucus secretion thanks to the Sympto-Thermal Method. This article gives a brief overview of how this method works and what makes it effective.


Return to NFP Science