Methods of family planning that are based on 'fertility awareness' try to identify the fertile days of a woman's menstrual cycle. Names used to describe this approach to birth control include 'rhythm,' 'natural family planning' and 'periodic abstinence.' The goal is to avoid sex on the days when the women might get pregnant. Couples could also use these methods with a condom or they could use withdrawal.
In February 2012, we did computer searches for randomized trials that examined family planning methods based on fertility awareness. For the original review, we also looked at studies mentioned in these trials as well as in review articles. We included trials that compared a fertility awareness-based method with a placebo ('dummy') or with another method including a different fertility awareness method. The test method could also be compared to a fertility awareness-based method used with another type of birth control.
Three studies were found; one was from Colombia and two were from Los Angeles, California. Due to weak methods, we could not analyze any data. Pregnancy rates could not be determined. The Colombia trial found similar numbers of women became pregnant in the ovulation and symptothermal groups. The Los Angeles trial observed more pregnancies in the group with the ovulation method. The USA trials found it hard to recruit couples, while the Colombia report did not mentioned that issue. Drop-out rates were high. In the two larger trials, most participants stopped their method early.
We still do not know how well these methods work for family planning. Even with a lot of training and support, most people in these trials stopped early. Birth control methods should be tested carefully before they are widely shared and used. Randomized trials are the best test of whether something works or not.
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.
'Fertility awareness-based methods' 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. Fertility awareness-based 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.
We retrieved and analyzed all randomized controlled trials (RCTs) that examined any fertility awareness-based methods used for contraception.
In February 2012, we searched the computerized databases CENTRAL, MEDLINE, POPLINE, and LILACS for randomized controlled trials of fertility awareness-based methods. We also searched for trials in ClinicalTrials.gov and ICTRP. Previous searches also included EMBASE. For the initial review, we examined the reference lists of trial reports as well as that of review articles.
We included all RCTs 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.
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.
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 USA 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.