The Standard Days Method (SDM) is an effective
new natural method of family planning developed
through scientific analysis of the fertile time
in the woman’s menstrual cycle. More than
95% effective for women with cycles between 26
and 32 days long, the SDM is easily provided by
a wide variety of programs. To use the SDM, a
couple tracks the woman’s menstrual cycle
and avoids unprotected intercourse on fertile
days 8 through 19 – if they want to avoid
a pregnancy. Most users of the SDM rely on CycleBeads®
, a color-coded string of beads, to help them
track their cycle and identify the days when pregnancy
is most likely.
An efficacy trial
found that the SDM was more than 95% effective
with correct use and more than 88% with typical
use among women who reported regular cycles of
26-32 days1. These effectiveness rates
are similar to those of a number of other user-dependent
methods
Contraceptive
Failure of User-Directed Methods*
Correct
Use
Typical
Use
No
Method
85
85
Spermicides
18
29
Diaphragm
6
16
Condom
2
15
OC
.3
8
Standard
Days Method
5
12
*% of women who
became pregnant during 1st year of use
Source: adapted
from Contraceptive Technology,
18th edition, 2004
Scientific Basis
The SDM is based on reproductive physiology. 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 of the life span of the sperm,
which remain viable in the woman’s reproductive
tract for up to five days, and the fact that the
ovum can be fertilized for up to 24 hours following
ovulation.
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 as early
as five days prior to ovulation and lasts up to
24 hours after ovulation.
Probability of Pregnancy from Intercourse
on Days Relative to Ovulation Source: Wilcox et al.
1998
Researchers at the Institute for Reproductive Health
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 the SDM to prevent pregnancy by avoiding
unprotected intercourse during the 12 fertile days identified
by the method.
