***N***atural Family Planning
Q.1. How effective are Natural Family Planning
Estimates of NFP effectiveness vary widely. NFP effectiveness depends upon several factors, including:
]The fertility indicator(s) used,
]The validity of the rules used,
]The type and quality of teaching,
]The ability of the woman to observe and interpret her fertility signs,
]The ability of the couple to abstain from vaginal intercourse when indicated by the rules, and
]Individual characteristics of the couple, such as the age of the woman and her history of pelvic infection or other determinants of lowered fertility.
[/list]**Calendar-based methodsEstimate: Estimates from clearly reported trials that state the rule used range from 5% to 14% in the first year of use. A recent reanalysis of calendar method clinical studies found a typical failure rate estimate of about 20%.
Rationale: It is difficult to estimate the effective- ness of the calendar method because very few well-designed studies have been conducted. Many of the estimates are based upon surveys and do not report the requisite information required to calculate effectiveness rates. It is difficult to compare studies on the calendar method because many reports do not state what rule was used to identify the fertile time or if couples understood the basis for the method (65, 165).
(basal body temperature (BBT),
cervical mucus or ovulation methods)**Estimate: Estimates range from 3% with perfect use to about 20% with typical use.
Rationale: The probability of accidental pregnancy when using single indicator methods is highest when couples do not abstain during the fertile period. For users of the cervical mucus or ovulation methods, having intercourse during periods of stress on the woman also increases the risk of pregnancy by affecting the quality of mucus. For users of the BBT method, stress, illness, travel, or interrupted sleep can disrupt a woman’s typical biphasic pattern, thereby making it difficult to identify the fertile period for that cycle using the body temperature (114, 275, 356).
**Two or more indicator methods
(symptothermal methods)**Estimate: Estimates range from about 2% with perfect use to about 15% to 20% with typical use.
Rationale: The use of two or more indicators can be somewhat more effective than the use of a single indicator (90, 114).
Data from 1996.