• Advantages:
• They can be used by most couples, provided that they are committed.
• Once learned, no further help is needed from healthcare providers.
• Once a method has been learned, it can be used to avoid pregnancy or to become pregnant, according to the couple's wishes.
• If there is no unprotected intercourse during the fertile time, the failure rate is about 0.6 per 100 women per 13 menstrual cycles [Frank-Herrmann et al, 2007].
• They do not involve use of chemicals or physical products.
• There are no physical or hormonal adverse effects, and there are no contraindications to their use.
• They can help the woman recognize normal and abnormal vaginal secretions.
• They involve men in the process and can help the woman to communicate about her fertility and sexuality.
• They are acceptable to all faiths and cultures.
• Initial and continuing costs can be low. However, fertility awareness devices can be expensive, and some require the purchase of consumables.
• They are immediately reversible.
• Disadvantages:
• They are only moderately effective as typically used — perhaps as many as 1 in 5 women will conceive within 1 year.
• They will not work without the continuing cooperation and commitment of both the woman and the man.
• To be optimally effective, they must be taught by someone trained to teach natural family planning.
• It takes two or three menstrual cycles to learn how to identify the fertile time accurately using cervical secretions and basal body temperature. Less time is required to learn the calendar method, but this method is more accurate if the woman has records of her to last six to twelve cycles.
• It is not suitable for women with irregular cycles.
• The woman must keep daily records of the fertility indicators she is following.
• Illness, lifestyle, stress, travel, and use of hormonal treatments can make fertility indicators hard to interpret.
• During the fertile time of the menstrual cycle, other contraceptive methods or abstinence need to be used.
• Natural methods do not protect against sexually transmitted infections, including HIV.
• Period abstinence requires the couple to avoid sexual intercourse for 8–16 days each menstrual cycle, which some people find difficult.
• Some devices and consumables must be bought by the woman.
• Risks:
• Fertility awareness–based methods in themselves carry no health risks to users or their babies.
• Women who have a condition that make the risks of pregnancy unacceptable should consider another, more effective contraceptive method [FFPRHC, 2006a].

[Hatcher et al, 1997a]