Natural birth control methods teach women to determine the fertile phase (typically 7 to 10 days long) of their menstrual cycle. To avoid pregnancy, women avoid intercourse on fertile days.
There are many variations of natural birth control. The most effective methods teach women to chart the signs of fertility that ebb and flow with the natural hormonal changes of each menstrual cycle. There are two main approaches 1) the sympto-thermal approach where waking temperature and cervical mucus are charted, and 2) the mucus approach where only cervical mucus is charted.
It is helpful for women and their partners to know about the two most common methods:
1. Fertility Awareness Method (FAM) refers to a natural birth control method outside of a religious framework that supports the use of barrier methods (condom, diaphragm, and spermicide), emergency contraception, and abortion. Justisse is a Canadian developed variant of FAM that teaches both the mucus only and the sympto-thermal approaches.
2. Natural Family Planning (NFP) typically refers to natural birth control that is taught and practised within a religious framework, most commonly Catholic centred organizations. It does not support the use of barrier methods, emergency contraception, or abortion. Billings Ovulation Method teaches only mucus observations. Serena and Couple to Couple League methods are sympto-thermal NFP variants. The Creighton Model will teach both mucus only and sympto-thermal approaches.
HOW NATURAL BIRTH CONTROL WORKS
The FAM/NFP sympto-thermal method is explained below.  It is considered the most effective of all the natural birth control methods.
Sympto-thermal teaches a woman how to observe, chart and interpret her waking temperature (basal body temperature or BBT) and cervical mucus to understand what days she is fertile and what days she is not fertile. She then knows when she is likely and when she is less likely to become pregnant from intercourse.
A woman who has a regular menstrual cycle will usually experience the following sequence of events:
3 to 7 days of menstruationseveral days where she does not feel or see mucus in her vagina or on her vulvaseveral days of a ‚Äòwet‚Äô or ‚Äòslippery‚Äô sensation at her vulva or in the vagina where she sees and/or feels mucus, which becomes progressively more slippery, stretchy, and clear as ovulation approachesafter ovulation her waking temperature rises, mucus disappears from the vulva, and the vulva and vagina feel ‚ÄúdrierFertile days begin with the first sensation of mucus at the vulva and continue until both the mucus has dried up and the waking temperature has been high for 3 days in a row.  With days of higher fertility and lower fertility determined, a woman can time intercourse to avoid or achieve pregnancy.
If a woman‚Äôs cycle does not follow a typical pattern, using natural birth control will be more difficult.  However, she can still use natural birth control but she is advised to seek consultation with a trained FAM/NFP instructor in order to use the method most effectively.  In general, FAM/NFP are not recommended for women with the following difficulties:  irregular cycles, inability to interpret the fertility signs correctly, or persistent infections that affect the signs of fertility.
Cervical changes are a third fertility sign that a woman may find useful in determining her fertility. She checks for variations in the position, firmness and openness of the cervix that relate to fertile and infertile days.
EFFECTIVENESS
In order to effectively use FAM/NFP a woman needs to accept responsibility for charting and interpreting her fertility on a day-to-day basis. The possibility of an unplanned pregnancy should not represent a devastating occurrence in order to use this method of family planning.  As with all forms of birth control, motivation, intention, and cooperation between partners are the key to effective, successful use.
Successful use of FAM/NFP methods depends on the accuracy of the method in identifying the woman‚Äôs actual fertile window, a woman‚Äôs/couple‚Äôs ability to correctly identify the fertile time, and  the couple‚Äôs ability to follow the instructions of the method they are using.  The effectiveness of FAM/NFP(Strauss and Barbieri 2004, Hatcher 2004.) varies depending on the method:
95-98% effective with perfect use (user strictly follows rules to avoid pregnancy)75-88% for typical use (user may not always follow rules)BENEFITS OF FAM/NFP
Effective method of birth controlHas no negative health side effectsAn alternative for women who cannot or do not want to use hormonal methodsPromotes positive body awarenessConsistent with many religious beliefs and lifestylesAlerts women to reproductive health and fertility concernsFosters communication between partnersEncourages partners to enjoy a variety of romantic or sexual activities as alternatives to vaginal intercourse during fertile periodsEncourages male involvementDISADVANTAGES OF FAM/NFP
Provides no protection from sexually transmitted infectionsOften difficult to find trained FAM/NFP instructorsRequires time to learn (usually 3 to 6 cycles)Requires discipline and commitment to chart fertility signs and follow the rules to avoid pregnancyTimes of abstinence from intercourse may be a challenge for some couplesOTHER NATURAL BIRTH CONTROL METHODS
Lactational Amenorrhea Method (LAM) is used by a woman who has just given birth and is exclusively breastfeeding. This method is highly effective for the first six months after childbirth, provided the woman breastfeeds the baby at least every four hours during the day and every six hours through the night, and that her menstrual period has not yet returned. After six months fertility may return at any time.
In the Temperature Method a woman takes her waking temperature to identify a rise in temperature indicating ovulation has passed. Elevated waking temperature for three days in a row is considered confirmation of the post-ovulatory less fertile phase.
Rhythm (Calendar) Method is a much less effective natural birth control method. It predicts a woman’s fertile days using calculations based on the length of past cycles and not daily observations of fertility signs as used by FAM/NFP. The Standard Days Method/Cycle Bead Systemis a variation of the Rhythm Method. These are the least effective natural birth control methods and are not generally recommended.