Table 26-1 Percentage of women experiencing an unintended pregnancy during the first yearof typical use and the first year of perfect use of contraception and the percentagecontinuing use at the end of the first year. United States.
% of Women Experiencing
an Unintended Pregnancy
within the First Year of Use% of Women Continuing
Use at One Year3

Typical Use1

Perfect Use2

8585

Spermicides

211642

Female condom6

21

5

41

Withdrawal

20

4

46

Diaphragm

171657Sponge171236

Parous Women

2720

Nulliparous Women

149Method
No method457

Fertility awareness-based methods

8Ovulation method8

1547

233144Standard Days method

125

Natural Cycles8

81

TwoDay method8
820.4

Male condom6

Symptothermal method

13243

Combined and progestin-only pills

70.367

Evra patch

70.367

NuvaRing

70.367Depo-Provera

40.2

56

ParaGard (copper T)

0.8

0.6

78

Skyla (13.5 mg LNG)

0.4

0.3

Kyleena (19.5 mg LNG)

0.2

0.2

Liletta (52 mg LNG)

0.1

0.1

Mirena (52 mg LNG)

0.1

0.1

Nexplanon

0.1

0.1

89

Tubal occlusion

0.50.5100Vasectomy

0.15

0.1

1008

Intrauterine contraceptives

80Emergency Contraceptives: Use of emergency contraceptive pills or placement of a copper
intrauterine contraceptive after unprotected intercourse substantially reduces the risk ofpregnancy. (See Chapter 10.)
Lactational Amenorrhea Method: LAM is a highly effective, temporary method of contraception.9(See Chapter 17.)
Source: See text.
(continued)

844 CONTRACEPTIVE EFFICACYCONTRACEPTIVE TECHNOLOGYTable 26-1 Percentage of women experiencing an unintended pregnancy during the first yearof typical use and the first year of perfect use of contraception and the percentage
continuing use at the end of the first year. United States.—(continued)
1

Among typical couples who initiate use of a method (not necessarily for the first time), the percentage who experiencean accidental pregnancy during the first year if they do not stop use for any reason other than pregnancy. Estimates of theprobability of pregnancy during the first year of typical use for fertility awareness-based methods, withdrawal, the malecondom, the pill, and Depo-Provera are taken from the 2006–2010 National Survey of Family Growth (NSFG) corrected forunder-reporting of abortion. See the text for the derivation of estimates for the other methods.

2Among couples who initiate use of a method (not necessarily for the first time) and who use it perfectly (both consistentlyand correctly), the percentage who experience an accidental pregnancy during the first year if they do not stop use for anyother reason. See the text for the derivation of the estimate for each method.

3

Among couples attempting to avoid pregnancy, the percentage who continue to use a method for 1 year.

4This estimate represents the percentage who would become pregnant within 1 year among women now relying on reversible
methods of contraception if they abandoned contraception altogether. See text.

5150 mg gel, 100 mg gel, 100 mg suppository, 100 mg film.

6

Without spermicides.

7

With spermicidal cream or jelly.

8

About 80% of segments of FABM use in the 2006-2010 NSFG were reported as calendar rhythm. Specific FABM methods
are too uncommonly used in the U.S. to permit calculation of typical use failure rates for each using NSFG data; rates provided for individual methods are derived from clinical studies. The Ovulation and TwoDay methods are based on evaluationof cervical mucus. The Standard Days method avoids intercourse on cycle days 8 through 19. Natural Cycles is a fertility appthat requires user input of basal body temperature (BBT) recordings and dates of menstruation and optional LH urinary testresults. The Symptothermal method is a double-check method based on evaluation of cervical mucus to determine the firstfertile day and evaluation of cervical mucus and temperature to determine the last fertile day.

9However, to maintain effective protection against pregnancy, another method of contraception must be used as soon as
menstruation resumes, the frequency or duration of breastfeeds is reduced, bottle feeds are introduced, or the baby reaches
6 months of age.

CONTRACEPTIVE TECHNOLOGYCHAPTER 26 845