Comparative evaluation of two methods of natural family planning in Columbia. A study of the vaginal contraceptive sponge used with and without the fertility awareness method. A randomized prospective study of the use-effectiveness of two methods of natural family planning.
Results of a comparative study of the ovulation method (OM) and symptothermal method (STM) of natural family planning in Colombia are presented. Recruitment of volunteer couples began in August, 1976, and continued through December, 1978, during which time 566 couples were randomly assigned to one or the other of the two methods. The study included 3 to 5 months of training in the method assigned, after which the couples entered the follow-up phase of the study. They remained in follow-up until (1) they dropped out or (2) the study closed in June, 1979. Total dropout rates were high for both methods of natural family planning. One year after entry into the follow-up phase of the study, net pregnancy rates were 24.2% for OM users and 19.8% for STM users. Gross pregnancy rates were 29.2% for OM and 26.1% for STM. Differences in pregnancy rates between the two methods were not statistically significant. The actual effectiveness rates of natural and barrier methods of family planning are lower than the theoretical ones. If couples accurately defined the limits of the fertile phase and used barriers at that time, then actual effectiveness might increase. A randomized, controlled clinical trial was initiated to determine the effectiveness of the contraceptive sponge used only during the fertile time and to compare this with sponge use at every intercourse. Recruitment problems and discontinuation forced the early termination of this study, but qualitative information about compliance and acceptability was collected. Common sponge problems were reported as were misuses of the sponge, but problems and misuse were not related. Determination of the fertile phase was reportedly easy, but complaints of and discontinuation for inconvenience occurred. For unplanned pregnancies, contraceptive behaviors around the time of conception are presented. The final results of a prospective comparative study of two methods of natural family planning indicate a significant difference in the 12 month net cumulative pregnancy rates between the ovulation and symptothermal methods. These differences are on the order of two to one in favor of the symptothermal method. Pearl pregnancy rates confirm similar differentials between the two methods. Dropout rates for both methods were high. Lack of interest or dissatisfaction with the method was the major reason for dropout training while pregnancy or desire for pregnancy were the major reasons for dropout during the formal phase of the study.
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.