There are several methods under the symptothermal umbrella term, and efficacy rates are based on learning with an instructor. I learnt with an instructor from fertility UK, this was very affordable for a lifetime of cycle knowledge and a year of chart support. The method involves me taking my temperature upon waking and observing my cervical fluid throughout the day, recording this information on a chart which I use to work out my fertile and infertile days. This method is easy to use once you have learnt. The number of infertile days is very dependant on the individual users cycle, but I typically get ten days where I can go unprotected once I have confirmed ovulation and also four days at the beginning of my cycle available to use. The rest of my cycle would be considered my potentially fertile/fertile days, where barrier methods (reducing the efficacy to that of the barrier) or abstinence/non penis in vagina sex would be necessary. A consideration is that the altered sexual behaviour would have to have the sexual partners cooperation too, as they would also have to be willing to use a condom or have alternative sex on the fertile days. I personally have found this method very empowering, having real-time data of what my body is doing and fertility status, working with my cycle phases instead of fighting against them. Learning about my body and reproductive health in ways that are not talked about in society and it is knowledge that should no be hidden from menstruators.