These methods require keeping consistent and accurate records. Some skill is required in figuring, and the margin for error depends on how accurately signs and records are interpreted and followed. It is most important that original explanations, early coaching, and frequent follow-up be done by a professional instructor or successful users. These methods work better for women whose cycles are always the same length. Some couples chart the woman s fertility pattern to prevent pregnancy because it is economical, safe, and can be discontinued easily when pregnancy is desired.
Little equipment is needed, and calendars, thermometers, and charts are widely available.
No medication is involved, which is especially appealing to women who have physical or health conditions that might make other forms of birth control less desirable or unsuitable. Medical checkups are not required, although professional instruction is important. Periodic abstinence is acceptable to most religious groups. However, if a couple decides to have vaginal intercourse during the fertile period, pregnancy is likely to occur unless they use barrier methods such as a combination of condom and foam. Charting fertility patterns requires dedication, education, and practice.