Contraceptive Effectiveness

The table below shows the percentage of women in the United States experiencing an unintended pregnancy during the first year of typical use and the first year of perfect use of contraception and the percentage continuing use at the end of the first year.

% of Women Experiencing an Unintended Pregnancy within the First Year of Use
% of Women Continuing Use at One Year3


Typical Use1

Perfect Use2


Chance4 85 85  
Spermicides5 26 6 40
Periodic abstinence 25   63
   Calendar   9  
   Ovulation method   3  
   Sympto-thermal6   2  
   Post-ovulation   1  
Withdrawal 19 4  
   Parous women 40 26 42
   Nulliparous women 20 9 56
   Parous women 40 20 42
   Nulliparous women 20 9 56
Diaphragm7 20 6 56
   Female (Reality) 21 5 56
   Male 14 3 61
Pill 5   71
   Progestin only   0.5  
   Combined   0.1  
   Progesterone T 2.0 1.5 81
   Copper T 380A 0.8 0.6 78
   LNg 20 0.1 0.1 81
Depo-Provera 0.3 0.3 70
Norplant and Norplant-2 0.05 0.05 88
Female sterilization 0.5 0.5 100
Male sterilization 0.15 0.10 100
Emergency Contraceptive Pills: Treatment initiated within 72 hours after unprotected intercourse reduces the risk of pregnancy by at least 75%.9

Lactational Amenorrhea Method: LAM is a highly effective, temporary method of contraception.10

Source: Trussell J. Contraceptive efficacy. In Hatcher RA, Trussell J, Stewart F, Cates W, Stewart GK, Kowal D, Guest F, Contraceptive Technology: Seventeenth Revised Edition. New York NY: Irvington Publishers, 1998, in press.

1 Among typical couples who initiate use of a method (not necessarily for the first time), the percentage who experience an accidental pregnancy during the first year if they do not stop use for any other reason.

2 Among couples who initiate use of a method (not necessarily for the first time) and who use it perfectly (both consistently and correctly), the percentage who experience an accidental pregnancy during the first year if they do not stop use for any other reason.

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

4 The percents becoming pregnant in columns (2) and (3) are based on data from populations where contraception is not used and from women who cease using contraception in order to become pregnant. Among such populations, about 89% become pregnant within one year. This estimate was lowered slightly (to 85%) to represent the percent who would become pregnant within one year among women now relying on reversible methods of contraception if they abandoned contraception altogether.

5 Foams, creams, gels, vaginal suppositories, and vaginal film.

6 Cervical mucus (ovulation) method supplemented by calendar in the pre-ovulatory and basal body temperature in the post-ovulatory phases.

7 With spermicidal cream or jelly.

8 Without spermicides.

9 The treatment schedule is one dose within 72 hours after unprotected intercourse, and a second dose 12 hours after the first dose. Preven is the only dedicated product marketed for emergency contraception in the United States (1 dose is 2 blue pills). The Food and Drug Administration has declared the following brands of oral contraceptives to be safe and effective for emergency contraception: Ovral (1 dose is 2 white pills), Alesse or Levlite (1 dose is 5 pink pills), Nordette or Levlen (1 dose is 4 light-orange pills), Lo/Ovral or Levora (1 dose is 4 white pills), Trivora (1 dose is 4 pink pills), Triphasil or Tri-Levlen (1 dose is 4 yellow pills).

10 However, 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 six months of age.

If you have questions about emergency contraception, please visit our page on frequently asked questions.