If pregnancy is to be postponed, it is recommended that sexual relations be avoided during the days of menstruation. Menstrual bleeding can conceal cervical mucus in a short cycle, making it possible to conceive during your menstrual period, particularly if your cycles tend to be short. The shorter the cycle, the earlier you ovulate.
Another reason for abstaining during menstruation is that recent medical evidence seems to indicate that sexual relations during the days of heavy menstrual flow may be responsible for the development of endometriosis in some women.
