Introduction

The length of periodic abstinence, due to overestimation of the fertile phase of the menstrual cycle, is often a cause for dissatisfaction, discontinuation, and user error with natural family planning (NFP) methods. The objective of this research was to compare the length of required abstinence (ie, estimated fertility) and coital frequency between 2 NFP methods.

Methods

This was an analysis of data from a 12-month prospective comparison study in which participants were randomized into either an electronic hormonal fertility monitor (EHFM) group or a cervical mucus monitoring (CMM) group—both of which included a fertility algorithm as a double check for the beginning and end of the estimated fertile window. The number of days of estimated fertility and coitus was extracted from each menstrual cycle of data, and t tests were used to compare the means of these 2 variables between the 2 NFP methods.

Results

The study involved 197 women (mean [SD] age 29.7 [5.4]) who used the EHFM to estimate the fertile window and 160 women (mean [SD] age 30.4 [5.3]) who used CMM to estimate the fertile window. They produced 1,669 menstrual cycles of data. After 12 months of use, the EHFM group had statistically fewer days of estimated fertility than the CMM group (mean [SD] days, 13.25 [2.79] vs 13.68 [2.99], respectively; t = 2.07; P = .039) and significantly more coitus (mean [SD] coital acts, 4.22 [3.16] vs 4.05 [2.88], respectively; t = 1.17; P = .026).

Discussion

The use of the EHFM seems to provide more objectivity and confidence in self-estimating the fertile window and using nonfertile days for intercourse when avoiding pregnancy.