Impact of instruction in the Creighton model fertilitycare system on time to pregnancy in couples of proven fecundity: results of a randomised trial

The Creighton Model FertilityCare System (CrMS) teaches women to identify days when intercourse is likely to result in pregnancy. We sought to assess the impact of the CrMS on time to pregnancy (TTP), via per-cycle pregnancy rates (fecundability).

We conducted a parallel randomised trial at the University of Utah School of Medicine, 2003-06. Women ages 18-35 years, in a relationship of proven fertility, who desired to conceive, were block-randomised and stratified for age, with allocation concealment by opaque sequentially numbered sealed envelopes. The control group received the advice to have intercourse 2-3 times per week, and the intervention group received CrMS instruction. All women were asked to begin trying to conceive starting the second cycle in the study and were followed actively up to seven cycles, without blinding of research personnel. We calculated descriptive statistics and fecundability, and estimated Cox models for TTP. (Clinicaltrials.gov NCT00161395).

There were 143 women randomised: 71 to the control group (all analysed) and 72 to the CrMS group (69 analysed). The adjusted hazard ratio for the influence of CrMS on TTP was 0.86 [95% confidence interval (CI): 0.53, 1.38]. Fecundability in cycles with intent to conceive was 31% in controls and 36% with CrMS (P = 0.32). By the first cycle, fecundability was 17% in controls, and 4% with CrMS (P = 0.02). No adverse events were reported.

We found no significant impact of CrMS on TTP or fecundability, but fewer of the women receiving CrMS conceived by the first cycle.