The sympto-thermal method

Natural birth control refers to the comprehensive way of life, while the term "sympto-thermal" refers to the method, on how the cycle of the woman is observed and evaluated.

Dr. Rötzer is referred in the scientific world literature as the founder of the first true sympto-thermal method.

What does sympto-thermal stand for?

The main sign ("symptom") of fertility is an increased mucus secretion from the vagina, called cervical mucus. It is formed on the fertile days in the neck of the uterus. The woman learns through daily monitoring to interpret this mucus as a sign of a potentially fruitful time.

Using the waking temperature ("thermal") the safe infertile time is then determined.

Additional signs ("symptoms") in the cycle process – they won’t be discussed further here - show valuable clues to the fertile and infertile times for each individual woman.


Already in 1968 the work of Rötzer showed the safety of use of the sympto-thermal method with a Pearl Index (PI) of 0.8. This safety-of-use-study was confirmed ten years later. In summary, both works of Rötzer show that no pregnancy in 17,026 cycles of 491 fertile-proven women, which are due to a systematic error (correct application of PI 0), has been occurred. There were 12 surprising pregnancies that were due to "user errors" (use safety PI 0.8).

J. Rötzer, Erweiterte Basaltemperaturmessung und Empfängnisregelung.
Archiv für Gynäkologie206, 195 -214 (1968)

ROETZER, Josef: The Sympto-Thermal Method: Ten Years of Change.
The Linacre Quarterly, The National Federation of Catholic Physicians’ Guilds,
Vol. 45, November 1978, NO.4, p.358 – 374"

" The reliability of the sympto-thermal method is according to experience - given it is used correctly - very high and reaches almost 100 percent. "
"This method goes back to the Austrian Rötzer".


Klinik der Frauenheilkunde und Geburtenhilfe,
Manual in 12 volumes, Volume 2, 3rd Edition 1996
Page 256, Verlag Urban & Schwarzenberg "

"The application of the sympto-thermal method according to ROETZER and THYMA offers high reliability.”

DÖRING, G.K.: Empfängnisverhütung – Ein Leitfaden für Ärzte und Studenten,
12. revised. Ed. (1990), page 24, Thieme-Verlag

"The symptothermal method (Rötzer 1968) is the combination of observation of the cyclical changes of the cervical mucus and measurement of the basal body temperature. (...) When used correctly, the symptothermal method with PI 0.3 is one of the safe contraceptive methods. It provides the most reliable and today's most frequently used method of natural family planning. Even with irregular cycles, this method can be applied."

Gynäkologie und Geburtshilfe Berlin:
Springer 2007, 2nd edition, page 130

"For patients with hormone-dependent breast cancer it has to be considered that estrogen-containing oral contraceptive ("pill") are contraindicated. In this situation it is important to know that there is an easily recognizable 100%-infertile time in the cycle of the woman (sympto-thermal method of natural conception regulation)."

Onkologische Krankenpflege,
4th Edition, Springer Verlag 2006
Chapter sexuality W. Rhomberg, M. Rhomberg, page 491/30