CONTENTS
HIGHLIGHTS
Spring, 2000
Series A, Number 9 |
Benefits of Oral Contraceptives Oral contraceptives have substantial benefits for women's health. The most important benefit, of course, is highly effective protection against pregnancy. OCs also help prevent ectopic pregnancy (pregnancy outside the uterus) and, by reducing menstrual blood loss, OCs lower the risk of iron deficiency anemia. In addition, they help to protect women from epithelial ovarian cancer and endometrial cancer and also may reduce the risks of bone density loss, ovarian cysts, benign breast disease, and colorectal cancer.
Fertility-Related Benefits
A World Health Organization (WHO) study that compared six combined OCs containing 20 to 50 µg of estrogen found no significant differences in effectiveness (533). Generally, among perfect users (women who miss no pills and follow instructions exactly), only 1 in every 1,000 women becomes pregnant in the first year of use (189). Among typical users, however, about 60 to 80 women in every 1,000 will become pregnant during the first year (189, 312). Progestin-only pills are slightly less effective than combined pills, except for breastfeeding women, for whom they are at least as effective (see sidebar, Progestin-Only OCs for Breastfeeding Women). Still, among perfect users of progestin-only pills who are not breastfeeding, only 5 pregnancies per 1,000 women occur in the first year of use. Typical-use rates are not available (190, 297). While progestin-only pills do not prevent ovulation in about half of menstrual cycles, other effects of progestins provide contraceptive protection. In particular, progestins thicken cervical mucus, making it more difficult for sperm to pass through the cervical canal (146, 297, 498). Some have speculated that multiphasics might be more likely to allow pregnancy if not used correctly, including taking them out of order (99, 134, 167, 239, 482, 512). Most clinical trials find no difference in effectiveness between multiphasics and constant-dose combined pills, however (124, 142, 371). Some women forget pills or stop them for a time. This largely accounts for the gap in OC effectiveness between perfect users and typical users. Irregular pill-taking may explain why users of oral contraceptives sometimes experience higher pregnancy rates than users of injectables, IUDs, or implants. According to Demographic and Health Survey data in 15 developing countries in the 1980s, the pregnancy rate among OC users was about 6 per 100 per year—twice the pregnancy rate among IUD users, at 3 per 100 (312). Long-term effectiveness of the pill requires sustained correct and consistent use. A recent review of 53 reports on contraceptive effectiveness concluded that on average about 7% of OC users are likely to become pregnant in the first three years of use, but the percentage varies depending on whether women take the pill correctly. Among the generally consistent and conscientious users, 3.8% would become pregnant within three years. In contrast, among those who use the pill inconsistently and incorrectly, 7.8% would become pregnant within three years (365). Preventing ectopic pregnancy. Protection against ectopic pregnancy is a benefit of all contraceptive methods, to varying degrees. Because they consistently stop ovulation, all combined OCs very effectively prevent ectopic pregnancies (117, 336). Ectopic pregnancy, which occurs when a fertilized ovum develops outside the uterine cavity, can be life-threatening (181). Ectopic pregnancy is fairly common. One US study found that ectopic pregnancy was the reason for 1 in every 13 emergency room visits during the first trimester of pregnancy (446). In the US ectopic pregnancy is the leading cause of pregnancy-related death in the first trimester. In 1992 ectopic pregnancies accounted for 2% of reported pregnancies and 9% of all pregnancy-related deaths in the US (478). |