Fertility Awareness-Based Methods Based on Life Table Analysis4–35
| Method | Women with Unintended Pregnancy Within 1 Year of Use (%) | Women Continuing Use at 1 Year (%) | Women with Unintended Pregnancy Caused by Unprotected Intercourse on Days Known Fertile Days (%) | ||
|---|---|---|---|---|---|
| Typical Use | With Barrier Backup * | Perfect Use | |||
| Calendar | |||||
| Rhythm † | 25 | 0.1–9 | |||
| Standard days ‡ | 12 | 5.7 | 4.8 | 46 § | 7.8 |
| Basal body temperature | 1 | ||||
| Cervical mucous | |||||
| TwoDays | 13.7 | 6.3 | 3.5 | 52.7 ‖ | 7.3 |
| Billings Ovulation ¶ | 10.5–22.3 | NT | 0.5 | 30.4–99.5 | 15.4 |
| Creighton/NaProEducation Technology | 17.1 ** | NT | 0.5 | 79.8–88.7 | 12.8 |
| Symptothermal ¶ | 0.2–20 †† | 0.45–2.3 * | 0.3 | 51.7–92.5 | 8.96 |
| Lactational amennorrhea ‡‡ | 2 | NA | NA | ||
↵* Fertility awareness-based methods defined more specifically as natural family planning do not report this data because it is considered abandonment of the method. Data is included where available.
↵† Estimated (definitive data not available).
↵‡ Limited to women with <2 cycles in 1 year outside of the 26- to 32-day range.
↵§ Twenty-eight percent discontinued because of 2 cycles outside 26- to 32-day range or 1 cycle longer than 42 days.
↵‖ Because of secretions >14 days or cycles <5 days (these are indicators of other potential health concerns), 15.7% asked to leave by study protocol. This loss also included women with cycles >42 days (n = 30) because of the cost of follow-up as well as women who failed to log symptoms for at least 12 cycles (n = 12).
↵¶ Typical use variable by study. More recent international studies show progressively lower unintended pregnancy rates and higher continuation rates.
↵** Overall pregnancy rate. Studies included women wishing to achieve pregnancy and made no attempt to distinguish planned vs unplanned pregnancies. Pregnancies resulting from intercourse on days known to the couple as fertile were counted as achieving related. Avoiding related pregnancies were 3.2% overall.
↵†† Lower typical failure rate with double-check method compared with single-check method.
↵‡‡ Perfect-use rate is for first 6 months only. LAM is ineffective as birth control if not used properly.
NT, not taught; NA, not applicable; LAM, Lactational Amennorrhea Method.