Slide
7
Because emergency contraception is used only once or
infequently, its effectiveness cannot be measured the way other
contraceptive methods that are used more frequently are measured. A more
accurate measurement of the efficacy of emergency contraception can be
obtained by comparing the number of pregnancies in a study with the number
of pregnancies that would have been expected without treatment. An
analysis of data from 10 studies (Yuzpe regimen) showed that the weighted
average of the effectiveness rates was 74%.
Hatcher et al 1998.
Slide 12
The risk of becoming pregnant depends on the day of the
woman’s cycle in relation to ovulation. Calculating the exact risk is
best done using data in which only a single act of intercourse potentially
could have led to conception. On the basis of 129 such cycles in the
Wilcox et al study, it was observed that the risk of pregnancy increased
from 8% at 5 days before ovulation to 36% on the day of ovulation. These
data indicate that the fertile period lasts only about 6 days, is
clustered around a 2 to 3 day interval (days -2 and 0) and ends on the day
of ovulation (i.e., cycle days 9 to 14 of a 28-day cycle). The decrease in
fertility immediately following ovulation (day 0) suggests a short
survival time for ova (less than 24 hours) as well as a rapid change in
the cervical mucus that may prevent entry of new sperm.
Use of emergency contraception during the fertile period
reduces the risk of pregnancy by at least 75%. For example, on day -2 a
36% risk might be reduced to about 9%.
For additional information, refer to: Blumenthal and
McIntosh. 1996. PocketGuide for Family Planning Service Providers,
2nd ed. JHPIEGO Corporation: Baltimore, Maryland.
Slide 13
Although the exact mechanism of EC is not clear, several
studies have shown that EC pills delay or inhibit ovulation and may
prevent implantation.
Slide 15
In developing countries, high-dose COCs are often not
available to use as emergency contraceptives. Therefore, low-dose COCs are
generally used.
Slide 16
Although the exact mechanism of EC is not clear, several
studies have shown that EC pills delay or inhibit ovulation and may
prevent implantation.
Slide 18
Because a woman has to take a total of 40 pills of
low-dose POPs to use as emergency contraception as compared to only 2
pills of high-dose POPs, it may be more difficult for the woman to take
the large number of pills. Therefore, high-dose POPs are generally
preferred, if available.
