Scientific Basis of the Symptothermal Method
The menstrual cycle is under the influence of complex hormonal activity:
At the beginning of the cycle the hypothalamus, situated in the brain, releases a stimulating hormone to the pituitary gland, wich is also situated in the brain. This hormone is called the gonadotropin releasing hormone (GnRH).
The pituitary gland then releases follicle stimulating hormone (FSH) that stimulates the ovaries.
The ovaries produce estrogen which matures the follicles.
Once the estrogen levels are increased to a certain level, the hypothalamus and pituitary gland receive positive feedback and as a response the pituitary gland releases luteinizing hormone (LH).
Under the influence of LH the follicle releases the ovum (ovulation).
Once the ovum has been released, the follicle transforms itself into the yellow body (aka corpus luteum) that will start to release progesterone, as well as some estrogen.
The two hormones continue to rise for about one week.
If conception did not occur during that cycle, the yellow body will begin to atrophy and the hormones begin to decrease for approximately one week until finally the corpus luteum dies and menstruation begins, thus day one of the next cycle.
Estrogen that is produced by the ovaries has a direct effect on the physical characteristics of the cervix and the cervical mucus. These characteristics are specific and observable daily and makes possible the determination of the beginning of the fertile phase of the cycle.
Once ovulation occurs, the high levels of progesterone in the body causes a mild increase in the core basal body temperature that will remain slightly elevated until menstruation begins. The influence of the progesterone in the body will also have an effect on the characteristics of the cervix and cervical mucus that are also observable. The changes to the cervix, cervical mucus and changes in the basal body temperature are what permit the user to identify the end of the fertile phase of that cycle.
Users of the Symptothermal Method document all their observable signs and daily temperatures on a chart. Users are then able to interpret the data and understand what is happening hormonally having learned the information and rules during a workshop taught by a certified instructor. Once users can determine the beginning and end of their fertile phases, they adapt their sexual activity depending on their objective of conceiving or not.
The symptothermal method, as taught by Seréna Québec, is highly effective with a rate of unplanned pregnancy of 0.4% when used consistently and correctly. This rate is comparable to that of the contraceptive pill and more effective than the condom.
To use the method correctly and achieve optimum effectiveness, one must follow a learning workshop with one certified trainer and rigorously and methodically apply the rules learned during the workshop.
TRUSSELL, James, Abigael AIKEN, Elizabeth MICKS et al. “Efficacy, Safety, and Personal Considerations”, dans Contraceptive Technology, HATCHER Robert et al (dir.), New York, Ayer Company Publishers inc., 2018, p. 100.