Oral contraceptives are indicated for the prevention of pregnancy in women who elect to use this product as a method of contraception. Oral contraceptives are highly effective. Table II lists the typical accidental pregnancy rates for users of combination oral contraceptives and other methods of contraception. The efficacy of these contraceptive methods, except sterilization, the IUD, and Norplant® System, depends upon the reliability with which they are used. Correct and consistent use of methods can result in lower failure rates. TABLE II: PERCENTAGE OF WOMEN EXPERIENCING AN UNINTENDED PREGNANCY DURING THE FIRST YEAR OF USE OF A CONTRACEPTIVE METHOD
Method Perfect Use Typical Use Norplant® System (6 capsules) 0.1 0.1 Male sterilization 0.1 0.15 Female sterilization 0.4 0.4 Depo-Provera®(injectable progestogen) 0.3 0.3 Oral contraceptives 3 Combined 0.1 NA Progestin only 0.5 NA IUD Progesterone 1.5 2.0 Copper T 380A 0.6 0.8 Condom (male) without spermicide 3 12 (female) without spermicide 5 21 Cervical cap Nulliparous women 9 18 Parous women 26 36 Diaphragm with spermicidal cream or jelly 6 18 Spermicides alone (foam, creams, jellies, and vaginalsuppositories) 6 21 Periodic abstinence (all methods) 1-9* 20 Withdrawal 4 19 No contraception (planned pregnancy) 85 85 NA - not available
*Depending on method (calendar, ovulation, symptothermal, post-ovulation)
Adapted from Hatcher RA et al., Contraceptive Technology, 16th Revised Edition. New York, NY: Irvington Publishers, 1994. In a clinical trial with levonorgestrel and ethinyl estradiol 0.10 mg/0.02 mg tablets, 1,477 subjects had 7,720 cycles of use and a total of 5 pregnancies were reported. This represents an overall pregnancy rate of 0.84 per 100 woman-years. This rate includes patients who did not take the drug correctly. One or more pills were missed during 1,479 (18.8%) of the 7,870 cycles; thus all tablets were taken during 6,391 (81.2%) of the 7,870 cycles. Of the total 7,870 cycles, a total of 150 cycles were excluded from the calculation of the Pearl index due to the use of backup contraception and/or missing 3 or more consecutive pills.