Effectiveness of Fertility Awareness-Based Methods for Pregnancy Prevention: A Systematic Review.

OBJECTIVE: To summarize best available prospective data on typical and perfect use effectiveness of fertility awareness-based methods for avoiding pregnancy.

DATA SOURCES: We conducted a systematic review of studies published in English, Spanish, French, or German by June 2017 in MEDLINE, EMBASE, CINAHL, Web of Science, and ClinicalTrials.gov.

METHODS OF STUDY SELECTION: We reviewed 8,755 unique citations and included 53 studies that contained 50 or greater women using a specific fertility awareness-based method to avoid pregnancy, calculated life table pregnancy probabilities or Pearl rates, and prospectively measured pregnancy intentions and outcomes. We systematically evaluated study quality.

TABULATION, INTEGRATION, AND RESULTS: Of 53 included studies, we ranked 0 high quality, 21 moderate quality, and 32 low quality for our question of interest. Among moderate-quality studies, first-year typical use pregnancy rates or probabilities per 100 woman-years varied widely: 11.2-14.1 for the Standard Days Method, 13.7 for the TwoDay Method, 10.5-33.6 for the Billings Ovulation Method, 4-18.5 for the Marquette Mucus-only Method, 9.0-9.8 for basal body temperature methods, 13.2 for single-check symptothermal methods, 11.2-33.0 for Thyma double-check symptothermal methods, 1.8 for Sensiplan, 25.6 for Persona, 2-6.8 for the Marquette Monitor-only Method, and 6-7 for the Marquette Monitor and Mucus Method. First-year perfect use pregnancy rates or probabilities among moderate-quality studies were 4.8 for the Standard Days Method, 3.5 for the TwoDay Method, 1.1-3.4 for the Billings Ovulation Method, 2.7 for the Marquette Mucus Method, 0.4 for Sensiplan, 12.1 for Persona, and 0 for the Marquette Monitor.

CONCLUSION: Studies on the effectiveness of each fertility awareness-based method are few and of low to moderate quality. Pregnancy rates or probabilities varied widely across different fertility awareness-based methods (and in some cases, within method types), even after excluding low-quality studies. Variability across populations studied precludes comparisons across methods.