Standard Days Method

Overview

The Standard Days Method (SDM) is based on fertility awareness; users must avoid unprotected sexual intercourse on days 8–19 of the menstrual cycle.^[337] Approximately 13 out of 100 SDM users become pregnant in the first year with typical use.^[28] SDM is reversible and can be used by patients of all ages. SDM does not protect against sexually transmitted infections (STIs), including human immunodeficiency virus (HIV) infection, and patients using SDM should be counseled that consistent and correct use of external (male) latex condoms reduces the risk for STIs, including HIV infection.^[31] Use of internal (female) condoms can provide protection from STIs, including HIV infection, although data are limited.^[31] Patients also should be counseled that pre-exposure prophylaxis (PrEP), when taken as prescribed, is highly effective for preventing HIV infection.^[32]

Use of SDM with various durations of the menstrual cycle

Menstrual Cycles of 26–32 Days

• The patient may use the method.
• Provide a barrier method (e.g., condoms) for protection on days 8–19, if they want one.
• If the patient has unprotected sexual intercourse during days 8–19, consider the use of emergency contraception if appropriate.

Two or More Cycles of <26 or >32 Days Within Any 1 Year of SDM Use

• Advise the patient that the method might not be appropriate for them because of a higher risk for pregnancy. Help them consider another method.

Comments and Evidence Summary

The probability of pregnancy when using SDM is increased when the menstrual cycle is outside the range of 26–32 days, even if unprotected sexual intercourse is avoided on days 8–19. A study examining 7,600 menstrual cycles, including information on cycle length and signs of ovulation, concluded that the theoretical effectiveness of SDM is greatest for women with cycles of 26–32 days, that the method is still effective for women who occasionally have a cycle outside this range, and that the method is less effective for women who consistently have cycles outside this range. Information from daily hormonal measurements demonstrates that the timing of the 6-day fertile window varies greatly, even among women with regular cycles.^{[38],[338],[339]}