Sinai, I., Lundgren, R. I., and Gribble, J. N. Continued use of the Standard Days Method. Journal of Family Planning and Reproductive Health Care 38 (2012):150-156.
Key Results
The method continues to be effective in the second and third years of use, and compares favourably to other user-directed family planning methods. Women with no more than two cycles outside the 26-32-day range within a year are likely to continue having cycles within this range.
Conclusion
Women who complete the first year of SDM use are likely to continue to be able to use the method successfully and effectively. The method presents a viable longer-term option for women who prefer this approach to family planning.