How Is It used?

Like traditional birth control pills, CBC is a series of pills containing synthetic hormones, estrogen and progestin, that are taken daily to prevent you from ovulating (releasing an egg to be fertilized). For most effective use, take each pill at the same time of the day.

Unlike traditional birth control pills that schedule 21 days of active pills followed by seven days of inactive pills, CBC allows you to take active pills continuously for three months.

During this time, CBC prevents the uterine lining from thickening enough to produce a full menstrual period. Every three months, you’ll take one week of inactive pills to produce a “pill period” that may be lighter than a regular period.

When you take CBC, expect to have four menstrual periods per year. However, you will have more bleeding and spotting between your menstrual periods than if you were taking a traditional birth control pill with a 28-day treatment cycle.

Does It Protect Against STIs?

STI stands for sexually transmitted infection. STI risk varies depending on how you choose to protect yourself and your partner during sexual or intimate activities.

CBC does not protect against STIs. The best way to protect against STIs while using CBC is to use a barrier method, such as condoms or dental dams.

Does It Protect Against Pregnancy?

Yes, CBC is highly effective as long as the pill is taken correctly every day. Pregnancy can occur if each pill is not taken correctly; for example:

• If you miss pills.
• If you start the pack late.
• If you take the pill at inconsistent times each day.

The more pills you miss, the more likely you are to get pregnant. As such, the chances of getting pregnant while using CBC are:

• Typical use: 5 percent
• Perfect use: 1 percent

Advantages and Disadvantages

Advantages:

• Fewer periods.
• Lighter periods with less blood flow.
• Some women with menstrual migraines or headaches benefit because they have fewer or less intense periods. 

Disadvantages:

• You must remember to take CBC every day without fail or it won’t be effective.
• It doesn’t protect against STIs.
• You are more likely to have spotting and breakthrough bleeding (light to fairly heavy bleeding between periods) than with a 28-day pill.
• It can be difficult to be sure you’re not pregnant without a monthly period.
• If you’re concerned, take a home pregnancy test. The test should show “positive” within 30 days of becoming pregnant; however, the test can show “negative” if you’re in an earlier stage of pregnancy. 

CBC carries some health risks similar to those with all birth control pills:

• Blood clots, stroke and heart attack.
• Cigarette smoking increases the risk of serious side effects.

Things to Remember

• During the first CBC treatment cycle, about one in three women may have 20 or more days of unplanned bleeding or spotting during active pills. This tends to decrease during later cycles.
• If you have no bleeding while taking the inactive pills, consider the possibility that you may be pregnant. Notify your healthcare provider that you’ve missed your period.

What If I Miss a Pill?

• If you miss one active pill, take it as soon as you remember. Take the next pill at your regular time. This means you may take two pills in one day.
• If you miss two active pills, take two pills on the day you remember and two pills the next day. Then take one pill a day until you finish the pack. You could become pregnant.
• You must use another birth control method as a backup on the seven days after you restart your pills. If you miss your period when you start taking the inactive pills, call your healthcare provider.
• If you miss three or more active pills in a row, do not remove the missed pills from the pack. Keep taking one pill every day as indicated on the pack until you’ve completed all the remaining pills. You must use another birth control method as a bac-up on the seven days after you restart your pills. If you miss your period when you start taking the inactive pills, call your healthcare provider.
• If you miss any of the inactive pills, throw away the missed pills and keep taking the scheduled pills until the pack is finished. Start your next pill pack on schedule.

Last Reviewed: January 2019