Menstrual Cycles Length of Women in the USA and Canada, 1990-2013

This datafile of start and end date of 3324 menstrual cycles of 581 women is part of a combined dataset of three cohorts of heterosexually active women who received instruction in the Creighton Model FertilityCare System (CrM) through centres across the United States and Canada. The CrM has standardised protocols for teaching women how to observe, record, and interpret daily vaginal discharge from bleeding and cervical fluid on a daily diary, called a CrM chart, and to use these standardised observations to identify the estimated time of ovulation and days when intercourse is likely to result in pregnancy.

The cohorts included: "Creighton Model Effectiveness, Intentions, and Behaviours Assessment" (CEIBA) (2009–2013), a prospective cohort of women without known subfertility, aimed to evaluate and classify pregnancy rates and pregnancy intentions during use of the CrM; "Creighton Model MultiCenter Fecundability Study" (CMFS) (1990–1996), a retrospective cohort of presumably fertile and subfertile women using CrM, aimed to assess the relationship between vulvar mucus observations and the day and cycle-specific probabilities of conception; and "Time to Pregnancy in Normal Fertility" (TTP) (2003–2006), a parallel-randomised trial, which aimed to assess the impact of CrM use on time to pregnancy in couples of proven fertility trying to conceive.