Yes. However the couples must be highly motivated, well-trained in their method, and committed to avoiding unprotected sex during the fertile time.
Are fertility awareness methods reliable?
For many couples, these methods provide reliable information about the fertile days. If the couple avoids vaginal sex, or uses condoms, a cervical cap or diaphragm during the woman's fertile time, fertility awareness methods can be effective. Using withdrawal or spermicides during the fertile time is less effective and not recommended.
How many days of abstinence or use of another method might be required for each of the fertility awareness methods?
The number of days varies based on the woman's cycle length. The average number of days a woman would be considered fertile and would need to abstain or use another method varies between 12 to 18 days dependent on the fertility awareness tracking methodology. To avoid an unintended pregnancy you must use another contraceptive method, such as condoms, during your fertile days.
How likely is a woman to become pregnant if she has sex during monthly bleeding?
During monthly bleeding the chances of pregnancy are low but not zero. Bleeding itself does not prevent pregnancy, and it does not promote pregnancy, either. In the first several days of monthly bleeding, the chances of pregnancy are lowest. As the days pass, the chances of pregnancy increase, whether or not she is still bleeding. The risk of pregnancy rises until ovulation. The day after ovulation the chances of pregnancy begin to drop steadily. Some fertility awareness methods that depend on cervical secretions advise avoiding unprotected sex during monthly bleeding because cervical secretions cannot be detected during bleeding and there is a small risk of ovulation at this time.