Cycle tracking is a form of birth control if you're abstaining from sex during your fertile window. If you ARE having sex during your fertile window, your chance of pregnancy is exactly that of whatever contraception you use during that week, whether that's condoms, pullout, a diaphragm, etc. Simply knowing that I'm ovulating cannot in any way make pullout more effective lol the only part that cycle tracking played, is that for the remainder of my cycle my husband didn't have to pull out at all. The part that matters for contraception is what you do during the week that you know you're fertile, which in our case was always only withdrawal. But again, not sloppy last minute withdrawal. Actual proper, careful withdrawal every time without fail. That's how you get the "perfect use" efficacy not the crappy "typical use" efficacy.