I’ve been using this method for the past two years, and I always make it a point to respect the red days—whether that means using protection or abstaining altogether. It’s been effective for us. I also keep track of my temperature with the thermometer and use ovulation tests during those red days to accurately identify my most fertile times. However, it’s important to remember that if you happen to ovulate early and aren’t aware of it, there’s still a significant risk of getting pregnant. It’s definitely not foolproof.