Perfect use: can be up to 99% effective if the natural family planning methods are followed precisely. These include monitoring cervical secretions and your basal body temperature. It's more effective if more than one method is used and it's taught by specialist teachers. Up to 1 in 100 women will get pregnant in a year when using this method perfectly.
Typical use: around 76% effective. Around 24 in 100 women using natural family planning will get pregnant in a year.
You should talk to your doctor or health professional as certain situations can affect fertility signs but also about risk factors such as smoking, your age or medical history before you decide on natural family planning as your method of contraception.