Schneider, M., & Fehring, R. J. (2012). Descriptive Statistical Evaluation of the Standard Days Method of Family Planning. The Linacre Quarterly, 79(4), 460-473. https://doi.org/10.1179/002436312804827064
Schneider M, Fehring RJ. Descriptive Statistical Evaluation of the Standard Days Method of Family Planning. Linacre Q. 2012;79(4):460-473. doi:10.1179/002436312804827064
Schneider, Mary, and Richard J. Fehring. "Descriptive Statistical Evaluation of the Standard Days Method of Family Planning." The Linacre Quarterly, vol. 79, no. 4, 2012, pp. 460-473.
Standard Days Method assumptions held for most regular cycles
A retrospective analysis of 714 cycles from 131 women with an electronic fertility monitor tested the fixed days 8 through 19 of the Standard Days Method. Estimated ovulation fell within three days of mid-cycle in about 81 out of 100 cycles.The fertile window reached outside days 8 through 19 in about 24 out of 100 cycles.
Study at a glance, retrospective analysis of 131 women: Standard Days Method assumptions held for most regular cycles. Source: Schneider M et al., 2012, PMID 30082989.
Key Findings
The estimated day of ovulation fell within three days of the cycle midpoint in 577 of 714 cycles (80.8%), and in 480 of 557 cycles (86.2%) lasting 26 to 32 days.
Ovulation fell within three days of the midpoint in 70 of 72 cycles (97.2%) shorter than 26 days and in 27 of 85 cycles (31.8%) longer than 32 days.
Part of the six-day fertile window fell outside days 8 through 19 in 172 of 714 cycles. That was 55 cycles before day 8 and 117 after day 19.
Among the 557 cycles of 26 to 32 days, 67 (12.0%) had part of the fertile window outside days 8 through 19.
Only 9 of the 55 cycles with fertile window days before day 8 (16.4%) showed a high reading on the fertility monitor on those days.
Interpretation
The authors analyzed charts already collected in a 12-month study of a monitor-based method for avoiding pregnancy. Participants averaged 29 years old and had no known fertility problems. The day of ovulation was estimated from the urinary LH surge, and cycles without a detectable surge were left out. The paper reports cycle timing and no pregnancy outcomes, so the results cannot show how well the Standard Days Method prevents pregnancy. The authors conclude it is valid for women whose cycles mostly last 26 to 32 days. The Georgetown institute that developed the method supported the analysis.
RRM Context
Fertility awareness-based methods locate the fertile window in different ways: fixed calendar days, hormone monitoring, or a woman's own daily signs. Ovulation day and cycle length rose together in this data set (r = 0.820). Ovulation moves from cycle to cycle. A method that reads each cycle's own signs follows the window where it falls.
Our editorial summary of this paper, not the article's abstract.
Abstract
The Standard Days Method (SDM) is a method of family planning that assumes ovulation to be close to the midpoint of the menstrual cycle; fertility falls between days 8 and 19; and is most effective for cycle lengths between twenty-six and thirty-two days. The purpose of this study was to evaluate the assumptions of the SDM with a new data set of 714 menstrual cycles produced by 131 women (mean age twenty-nine) who tracked their fertility with an electronic fertility monitor that measured urinary estrogen and luteinizing hormone (LH). The LH peak was used to estimate the day of ovulation (EDO) and the six-day fertile window. Results indicated the majority (80 percent) of menstrual cycles had EDOs within three days of the midpoint of the cycle (86 percent with cycle lengths between twenty-six and thirty-two days). Approximately 22.5 percent (172) of the cycles had fertile window days outside of days 8 to 19, 10.2 percent (78) before, and 12.1 percent (92) after. However, there is a low probability of pregnancy when women experience short cycles and the early days of the fertile window are outside of days 8 through 19. We concluded assumptions of the SDM outside of the fertile window with long cycles could be problematic. However, the SDM is valid for women who have most cycles within the twenty-six to thirty-two day range.
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