Standard Days Method (SDM)
The Standard Days Method is a calendar method that treats cycle days 8 through 19 as fertile. It was designed for women whose cycles run 26 to 32 days. A woman counts days rather than observing a biomarker.1
The fixed count fits many cycles and misses others. In an analysis of 714 cycles, part of the fertile window fell outside days 8 through 19 in about 24 of every 100 cycles.2
A calendar cannot say what one woman's ovary did this month. Restorative care rests on charting a woman's own cycle, because that chart doubles as clinical data.
Cited in this entry
- Arévalo M, Sinai I, Jennings V. A fixed formula to define the fertile window of the menstrual cycle as the basis of a simple method of natural family planning. Contraception. 1999. https://pubmed.ncbi.nlm.nih.gov/10715371/
- Schneider M, Fehring RJ. Descriptive Statistical Evaluation of the Standard Days Method of Family Planning. The Linacre Quarterly. 2012. https://pubmed.ncbi.nlm.nih.gov/30082989/
This content is for educational purposes only and does not constitute medical advice. Consult an RRM clinician or healthcare provider for guidance specific to your situation.
