Natural Family Planning (NFP) is the all natural way of deciding how many children you will have and how far apart they will be spaced that is in keeping with the teaching of the Catholic Church. When done correctly, NFP can be as effective as artificial contraception. For many years, doctors and researchers have been studying a woman’s body to see how her hormones, temperature, and fluids respond to different stages of her monthly cycle. By knowing how a woman’s body works optimally, a couple use that information to determine their own fertility.