During those days it is unsafe to have unprotected intercourse without risking pregnancy. Fertility awareness techniques can be used to prevent or to plan a pregnancy and are acceptable to couples with religious concerns about birth control. The method requires keeping a daily chart of body changes and it needs expert instruction for successful use. A fertility awareness method with abstinence requires the self-control of both partners. Even with correct use, failure may be more likely than with other methods.
Frustration can result from long periods of abstinence.
In the basal body temperature method, abstinence must last from menstruation until after ovulation. Body temperature is taken each morning before getting out of bed. A small but significant rise of less than one degree occurs when the egg is released. After three days of the higher level, the unsafe period is past. The vaginal mucus system associates changes in a woman's vaginal moisture with phases of her menstrual cycle.