Fertility Apps are the next development for Fertility Awareness Based Methods. FABMs.
It is an exciting development and are very attractive on the iPad or iPhone.
Many are like a diary or calendar. They just record the dates of the menstrual cycle and do not try to predict the fertile and infertile phases of the menstrual cycle.
But others record some of the 4 fertility signs and then try to predict the fertile phase. Pregnancy can result from the too late prediction of the onset of fertility. Sperm may already be in the vagina and uterus when she is in fact fertile. Sperm can live for 7 days in good a good environment.
Each woman should learn to track her own signs, preferably with her own Teacher who has been trained to teach. She will then be taught to interpret her fertility signs and to interpret them reliably.
Up to now NFPTA have not found that any App that is as reliable as charting, though we are keeping an open mind. Watch this space.