Trial of a new method of natural family planning in Liberia

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.

Fertility awareness-based methods for contraception

BACKGROUND

"Fertility awareness-based methods" (FAB) of family planning "involve identification of the fertile days of the menstrual cycle, whether by observing fertility signs such as cervical secretions and basal body temperature, or by monitoring cycle days. FAB methods can be used in combination with abstinence or barrier methods during the fertile time" (WHO 2000). Several names have been used to describe this approach to contraception, including "rhythm," "natural family planning" and "periodic abstinence." Fertility awareness-based methods can be used with abstinence from sexual intercourse. Alternatively, they can be used with barrier contraceptives or withdrawal during presumed fertile times.

OBJECTIVES

We retrieved and analyzed all randomized controlled trials that examined any fertility awareness-based methods used for contraception.

SEARCH STRATEGY

We searched the computerized databases Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, POPLINE, EMBASE, and LILACS (each from its inception to January, 2004) for randomized controlled trials of fertility awareness-based methods. We examined the reference list of each trial as well as that of review articles.

SELECTION CRITERIA

We included all randomized controlled trials in any language that compared any fertility awareness-based methods for contraception with a placebo; another method, including an alternative fertility awareness-based method; or fertility awareness-based methods used in conjunction with another contraceptive.

DATA COLLECTION AND ANALYSIS

We assessed all titles and abstracts found for inclusion. We evaluated the methodological quality of the trials for potential biases by qualitatively assessing the study design; randomization method; allocation concealment; blinding; premature discontinuation rates; and loss to follow-up rates. Because of methodological weaknesses, we could not enter the trial results in RevMan, calculate measures of association, or aggregate data.

MAIN RESULTS

Because of poor methods and reporting, pregnancy rates could not be determined. A trial in Colombia found similar numbers of pregnancies among women randomized to the ovulation and symptothermal methods. In contrast, a companion trial in Los Angeles observed more pregnancies in the group assigned to the ovulation method. In the two U.S. trials, recruitment of participants was unexpectedly difficult; this aspect was not mentioned in the report from Colombia. Continuation rates were poor. In the two larger trials, most participants discontinued their assigned method before entering the observation phase of the trial.

REVIEWERS' CONCLUSIONS

The comparative efficacy of fertility awareness-based methods of contraception remains unknown. Despite intensive training and ongoing support, most participants in these trials discontinued prematurely. Contraceptive methods should be properly evaluated, preferably in randomized controlled trials, before adoption and dissemination.