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How Do Progestin-Only Birth Control Pills Work?

Progestin-only birth control pills work by delivering a consistent dose of the hormone progestin. When this hormone enters the body, it performs several main functions that stop you from getting pregnant:

  • It thickens the mucus in the cervix so that sperm aren’t able to make it to the uterus to fertilize your egg.
  • It thins the lining of the uterus, so even if an egg does become fertilized, it will not be able to implant.
  • In some women, it stops ovulation, meaning you won’t release an egg that month, and therefore, can’t get pregnant.

Most progestin-only birth control pills work on a 28-day cycle. Unlike combination birth control pills, which sometimes have a week of inactive pills, all of the pills contain progestin to keep your hormone levels regulated, so it’s important that you don’t skip taking the pill any days.

You also need to take the pill at the same time each day, as your body may not properly absorb the progestin if you alter your schedule. If you are three or more hours late taking your pill, you’ll want to use another form of birth control for the next two days to make sure you don’t get pregnant. And, if you’ve had sex three to five days prior to missing your pill, you’ll want to consider using emergency contraception to ensure pregnancy doesn’t occur.

When taken correctly, progestin-only birth control pills work great. In fact, they are just as effective as combination pills, patches, and rings.

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