Efficacy & Scientific Basis of SDM
Efficacy of SDM
A multi-site efficacy trial found that the Standard Days Method®(SDM) was more than 95% effective with correct use among women who had regular cycles of 26-32 days. With typical use, the SDM is 88% effective. These efficacy rates are similar to those of other user-dependent methods. The efficacy study had 478 enrolled women, age 18-39, and took place in Bolivia, Peru, and the Philippines.
PREGNANCY RATES DURING ONE YEAR OF USE (%)
| Method | Correct Use | Typical Use |
|---|---|---|
| No Method | 85 | 85 |
| Spermicides | 18 | 29 |
| Standard Days Method | 5 | 12 |
| Condoms | 2 | 15 |
| Oral Contraceptives | 0.3 | 8 |
| Injectables | 0.05 | 3 |
Source: Family Planning: A Global Handbook for Providers, 2007
Scientific Basis of SDM
SDM is based on reproductive physiology. Most ovulations occur around the mid-point of the menstrual cycle (+/- 3 days). Thus a woman's fertile "window" (days in the menstrual cycle when she can get pregnant) begins approximately five days prior to ovulation and lasts up to 24 hours after ovulation. This is because sperm remain viable in the woman’s reproductive tract for up to five days, and the ovum can be fertilized for up to 24 hours following ovulation.
Researchers at IRH identified the fertile window in the woman’s menstrual cycle, using a computer simulation that took into account the probability of pregnancy, probability of ovulation occurring on different cycle days, and variability in cycle length from woman to woman and from cycle to cycle. Their analysis found that avoiding unprotected sex on days 8 through 19 of the cycle provided maximum protection from pregnancy while minimizing the number of days to avoid intercourse.
Women with menstrual cycles between 26 and 32 days long can use SDM to prevent pregnancy by avoiding unprotected intercourse during the 12 fertile days identified by the method.
SDM is a Modern Method of Family Planning
In addition to providing significant protection from unintended pregnancies, modern methods of family planning share certain characteristics, including that they:
- are based on a sound understanding of reproductive biology,
- follow a precise protocol for correct use, and
- have been tested in an appropriately designed study to assess efficacy under various conditions.
SDM meets these criteria and as such, is regarded as a modern method by international organizations and ministries of health around the world. Read the technical brief, which details further justification, in English or Spanish.
