Particularly because so many couples rely on the pill, ensuring its effective use is important to fulfilling people's reproductive goals. OCs are unique among contraceptives in that their full effectiveness requires the user's daily action. No other method requires the user to act on a daily basis, even when no sexual contact takes place.

When taken consistently and correctly, OCs are one of the most effective methods. In actual use, however, OCs are not as effective at preventing pregnancy as they could be. If family planning programs and health care providers paid greater attention to helping women use the pill, the actual effectiveness of OCs could improve substantially.

Strategies to improve pill use include giving women complete and easily understood information, providing individual counseling, and offering frequent follow-up messages to remind women about effective pill use. Mass media campaigns that inform people about family planning can foster social approval of it and educate people about available methods. Making pills accessible and removing any unnecessary restrictions to their safe use also can help women use the pill more effectively.

Bangladesh Family Planning Directorate

In Bangladesh and around the world, millions of women rely on OCs. Among methods, only OCs requires a user's daily action to be fully effective.

For combined OCs, which contain both progestin and estrogen, the perfect-use pregnancy rate is estimated at just one pregnancy per 1,000 women, or 0.1 per 100, in the first 12 months of use. For the progestin-only pill, the perfect-use pregnancy rate is estimated at five pregnancies per 1000 women, or 0.5 per 100, in the first 12 months of use (223).

Typical-use pregnancy rates for OCs* are generally much higher. National surveys in 21 countries found that typical-use pregnancy rates among OC users ranged from 1.7 pregnancies per 100 women in Bangladesh to 10.5 per 100 women in Bolivia in the first 12 months of use (see Figure 1). In the US the pregnancy rate among OC users in 1995 was 6.9 per 100 women over 12 months (225).

Longer-term users of OCs tend to be more effective users, possibly both because of experience and because less successful users have become pregnant, discontinued use, or switched to a different method. In five of seven countries with data for 24 months of pill use, pregnancy rates were lower in the second year than in the first year (4, 225). Over two years, rates ranged from 4.5 pregnancies per 100 OC users in Thailand to 16.5 pregnancies per 100 OC users in Egypt (4).

While some typical one-year pregnancy rates may seem modest, even low levels of contraceptive failure each year can mean that over the long term many women will have unintended pregnancies. If the pregnancy rate for the pill is 6% per year among a group of pill users, for example, nearly half would experience unintended pregnancy within 10 years (184). Over 18% of users would become pregnant after 10 years at a 2% pregnancy rate per year, while an annual pregnancy rate of 10% would result in 65% of users experiencing unintended pregnancy over 10 years.

Based on estimates of worldwide pill use for 2000, in one year at least 2 million women become pregnant unintentionally because they do not take the pill effectively (see side-bar, Most Pill Users' Pregnancies Occur When They Quit but Do Not Switch). If even just 1 more woman in every 10 used OCs effectively, there would be 200,000 fewer unintended pregnancies.

As typically used, the pill is less effective in preventing pregnancy than such other reversible methods as intrauterine devices (IUDs) and injectables. Yet, if used perfectly, the pill would be among the most effective methods—slightly more effective than the copper T IUD, progestin-only injectable contraceptives, and female sterilization. In fact, only Norplant implants have an expected perfect-use failure rate lower than that of combined OCs (223).

*Unless noted otherwise, the term “OCs” as used in this report indicates combined oral contraceptives. Most studies of typical use, however, do not specify whether rates are for progestin-only pills, combined OCs, or both. Since most pill users take combined OCs, it can be assumed that these data largely reflect rates for combined pills.