What is the Symptothermal Method?
The symptothermal method is a well-studied, highly effective form of fertility awareness. Unlike traditional "rhythm methods" that simply guess based on a calendar, the symptothermal method relies on real-time biological data from your own body.
How does it work?
Your body gives off very clear signals as it progresses through your menstrual cycle, specifically surrounding ovulation. The symptothermal method tracks two primary symptoms (hence the name):
- Thermal (Temperature): A slight, sustained rise in your Basal Body Temperature (BBT) occurs after ovulation, caused by the hormone progesterone.
- Symptom (Cervical Fluid): Changes in your cervical fluid (or mucus) indicate when you are approaching ovulation. As estrogen rises, the fluid becomes clear, slippery, and stretchy (often compared to raw egg white), which keeps sperm alive and helps it travel.
Why is it effective?
When practiced correctly with careful tracking, the symptothermal method is highly effective for both achieving and avoiding pregnancy. By cross-referencing your temperature shift (which confirms ovulation has passed) with your fluid observations (which warn that ovulation is approaching), you get a highly accurate picture of your fertile window.
Most predictive period apps (the calendar methods) simply count days. They assume every cycle is exactly the same length, which is rarely true. Stress, travel, and illness can all delay ovulation. The symptothermal method doesn't guess—it observes what is actually happening.
How effective is the symptothermal method?
It's one of the most-studied fertility-awareness methods. In a large German study (Frank-Herrmann et al., 2007, published in Human Reproduction) that followed 900 women across more than 17,000 cycles, couples who learned the method and used it correctly saw about 0.4–0.6 unintended pregnancies per 100 women per year — a method effectiveness of roughly 99.4% with perfect use. Including couples who had unprotected sex during the fertile window, the overall (typical-use) rate was about 1.8 per 100 women per year.
One caveat that matters, and that we won't gloss over: those numbers describe the method — taught properly and practised carefully — not any single app. canihavesex.today helps you log and interpret your signs conservatively, but it is a guide, not a contraceptive, and it doesn't replace learning the method itself. It also isn't medical advice.
How canihavesex.today uses the method
Our app is designed to help you easily log these two primary signs: your waking temperature and your daily fluid observations.
We apply a strict, conservative interpretation of the symptothermal rules. If your data is unclear—perhaps you missed a few temperature readings or your fluid signs are mixed—the app will not guess. It will simply tell you that the current status is unknown. We believe that when it comes to fertility, "I don't know" is a much safer answer than a false positive.
Getting Started
To get started, you'll need a Basal Body Thermometer (a thermometer that reads to two decimal places, e.g., 97.54°F). Take your temperature every morning immediately upon waking, before you get out of bed, and log it in the app. Throughout the day, observe your cervical fluid and log the most fertile type you see. Over a few cycles, you'll begin to see clear, unmistakable patterns.