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.
PIP: A comparative study of the use-effectiveness of the OM (ovulation method) and the STM (symptothermal method) of natural family planning was conducted in Bogota and Palmira, Colombia. The pregnancy rates obtained in the study were high for both methods and no significant difference was observed in the pregnancy rates for couples using the OM and for couples using the STM. The study was initiated by the government and the Javeriana University, sponsored by the World Health Organization, and designed and analyzed by the Department of Biostatistics of the University of North Carolina. The planned study was widely publicized and couples were urged to volunteer as study participants. 544 couples, who meet specified requirements, were recruited and randomly assigned to receive training in either the OM or the STM. Training lasted from 3-5 months. 57% of the participants dropped out during the training phase. The remaining 241 couples were then included in the formal follow-up phase of the study and were followed-up monthly for 1 year. Pregnancy rates were computed using both the life table method and the Pearl method. The net cumulative drop-out rate after 1 year of follow up for the 241 couples was 60.1% for OM users and 53.0% for STM users. Net cumulative rate of voluntary withdrawal was 30.3% for OM users and 26.0% for STM users, and the net cumulative pregnancy rate was 24.2% for OM users and 19.8% for STM users. The Pearl pregnancy rate was 33.8/100 users for the OM and 26.0/100 users for the STM users. There were no significant differences in the characteristics of OM and STM participants who took part in the follow-up phase nor between OM and STM drop-outs. The high drop-out and pregnancy rates observed in this study suggested that natural family planning was probably not an effective form of contraception for a large proportion of the Colombian population.