You may not have heard of these pills even though they have been available for 25 years in the U.S. They are similar to birth control pill which is called a combination pill since it contains two types of female hormones. The progestin only pill has just the one hormone. Three brands are marketed in this country: Micronor, Nor QD and Ovrette.

Advantages:

• Since it contains no estrogen, it can be used in women who smoke.
• It has fewer side effects than the combination pill. For example, it never causes nausea.
• It may be better for women who are breast-feeding.
• It may be better for women with diabetes.
• It's about 95% effective in preventing pregnancy.

Disadvantages:

• It must be taken exactly every 24 hours.
• Irregular bleeding is common.
• Some women have no periods at all, which makes it hard to tell if pregnancy has occurred.
• About 5% of women get pregnant on this method.
• If a woman does get pregnant, the chance of an ectopic pregnancy is quite high. These types of pregnancies can require major surgery.