A randomized prospective study of the use-effectiveness of two methods of natural family planning: an interim report.

Data accumulated to date from the Los Angeles study indicate that the total termination rate for 12 months from the beginning of the training period and from formal entry into the study was high for the ovulation method (OM), and symptothermal method (STM). Voluntary withdrawal was the highest single reason for termination in both methods. The 12 month voluntary withdrawal rate, measured from formal entry into the study, was significantly higher for OM users. Pregnancy rates measured from both the beginning of training and formal entry into the study were significantly higher for OM users than for STM users. Complete analysis of the data collected during the study is currently in progress. It is anticipated that some of the causes for the differences in pregnancy rates and withdrawal rates between the two methods can be identified.