Understanding effectiveness estimates for fertility awareness based methods of contraception

In May 2017, Natural Womanhood and FACTS put out a call for people to sign their petition asking CDC to “update its website to reflect the best data available and to cite the individual effectiveness rate of each unique type of evidence-based fertility awareness based method (FABM)”, asserting that the CDC website currently “misrepresents the actual effectiveness of individual modern FABMs” by reporting a typical failure rate for all FABMs of 24%. They state that data on effectiveness of FABMs on the CDC website is based on “one study with a low quality research design, which explains why its conclusions are so far from what quality studies show us”. They posit “bias” in this estimate as it is based on a retrospective survey, and as it lumps together variants of calendar rhythm plus other FABMs. The assertions in this petition raise multiple concerns (outlined below).

Read More