Efficacy of the Standard Days Method of Family Planning

The Standard Days Method® is a fertility awareness-based method of family planning. Users avoid unprotected intercourse during cycle day 8 through cycle day 19. The method is most effective for women with cycles that usually range 26-32 days. It was developed by applying various formulae (i.e. various numbers of days and various sets of days) to over 7500 menstrual cycles in an existing data set from the World Health Organization, to determine which formula would provide the optimal balance between he length of the identified fertile period and the efficacy in avoiding unplanned pregnancy.

The purpose of the clinical trial was to test the efficacy of the method in preventing pregnancy.

Participants were from five sites in Bolivia, Peru, and the Philippines. In all sites, the Institute for Reproductive Health trained 5-10 health workers (service providers) in teaching the Standard Days Method to study subjects and in study procedures. Method provision involved a counseling session in which the woman (or the couple, if her partner was available) was instructed in the use of the method, and counseled on the importance of following the method recommendations to avoid pregnancy.

To assist women in monitoring their cycles, the provider gave them CycleBeads® a mnemonic device, a string of 32 beads in which each beads represents a day of the menstrual cycle. The first bead is red, representing the first day of menses; the next 6 beads are brown, representing the additional non-fertile days preceding the fertile window; the next 12 beads are white, representing days that should be considered fertile (8-19); and the remaining 13 beads are brown, again representing non-fertile days. It also has a moveable, tight-fitting rubber ring that is used to mark the current day of the cycle. Women were instructed to place the ring on the red bead on the day their menses began, and move the ring one bead per day until their menses returned. They also were told that to avoid pregnancy they should not have unprotected intercourse on the days the ring was on a white bead. If they had menstrual bleeding before day 27 of the cycle (i.e., a cycle shorter than 26 days), or if their menses had not occurred by the day after they completed all 32 beads (i.e., a cycle longer than 32 days), they were instructed to contact their provider for further assessment and advice. Women who had two cycles outside the 26 through 32 day range during the study period were advised to use another method, and were withdrawn from the study.

A total of 478 women wishing to use the Standard Days Method and meeting the eligibility criteria were admitted to the study after signing an informed consent form and interviewed monthly until they either completed 13 cycles of method use or left the study for other reasons. The first level of data collection was administered by the clients themselves. Each woman was asked to keep a daily diary to record menstrual bleeding, intercourse, and use of any other contraceptive method. The information on the diary card was reviewed by the clients and the service provider during each of the monthly follow-up contacts. In addition, follow-up forms were administered, which included questions concerning method use, satisfaction, and willingness to continue in the study.

Women who had not had their menses by day 42 of their cycle were tested for pregnancy. If results were negative, they were followed until they tested positive or their menses returned. Loss to follow-up was minimized by interviewing study participants in their homes and actively seeking out each participant, with a minimum of three attempts per cycle.

Single-decrement multi-censoring life tables were used to calculate pregnancy rates.