Chapter 16: Measuring Effectiveness and Pregnancy Rates of the CrMS

This chapter describes how the effectiveness and pregnancy rates of the CREIGHTON MODEL FertilityCare™ System (CrMS) are measured during use to avoid or to achieve pregnancy, including the features of a good effectiveness study and a summary of published CrMS studies. The chapter states that CrMS studies use a behavioral approach to distinguish use to avoid from use to achieve pregnancy, whereas most other studies of NFP and contraception use an intentional approach, and it describes the CrMS classification of pregnancies as achieving related, avoiding related, or unresolved. The chapter explains that the achieving-related pregnancy rate is a demographic measure whose denominator includes many couples who never try to achieve pregnancy, and it proposes a new approach in which each rate counts only the cycles in which that type of use is occurring. Summarizing the 1998 five-study meta-analysis, the chapter states that the CrMS has excellent method effectiveness and user effectiveness and that user effectiveness improved over the time of the five studies.