anonymous on August 30, 2011

How good is the Pill at preventing pregnancy?

My girlfriend is on the Pill and we use condoms...but the last time we had sex, the condom came off. It was 13 days before she expects her period. Is it possible for her to get pregnant because the condom slipped off? Should we get the “morning after” pill?

answered by Lisa Oldson, MD on August 30, 2011

Thanks for sharing your concern. I’ll do my best to help.

When used correctly, the Centers for Diseases Control and Prevention (CDC) report that the Pill is up to 99% effective. However, in the real world, people sometimes skip pills or don’t follow birth control pills fail about 8% of the time.

In other words, in studies that have looked at birth control effectiveness, out of 100 couples who used birth control pills for a year as their only form of contraception, eight of those couples ended up becoming pregnant.

Because you and your girlfriend have been using condoms in addition to birth control pills, the risk of an unintended pregnancy is low. However, that assumes that your girlfriend has been taking her birth control pills daily, at close to the same time every day.

You asked if you should look into the morning after pill, also called emergency contraception (EC). EC is a larger dose of hormones similar to those in birth control pills, but it’s not meant to be used as a regular form of birth control...and, as you probably know, it should only be used if your regular form of birth control fails.

Because your girlfriend is already taking birth control pills, using EC probably isn’t necessary. That said, if she hasn’t been on the Pill for very long, or if she hasn’t been taking the pills consistently, and your condom slipped off during sex, one of your options to prevent potential pregnancy would be the morning after pill. In most states, EC is available to people 17 and older without a prescription.

Your girlfriend may also want to take a home pregnancy test, and confirm the results with her doctor.

One more thing for you to consider...

It sounds like you were using a condom to prevent pregnancy, but what about STDs? Condoms and dental dams are the best way to reduce the risk of spreading sexually transmitted diseases (STDs), so I commend you for being smart about both pregnancy and STD protection. But if you or your girlfriend have ever had sexual contact with someone else, you may want to get tested for common STDs.

Remember, most STDs don’t cause symptoms right away, but some can cause lasting health problems without proper treatment. Once you know each other’s STD status, you’ll be better informed to take care of each other’s sexual health.

For information about STD risks, symptoms, prevention and treatment, check out our Expert Guide to STD Basics.

Thanks again for writing in, and I wish you and your girlfriend the best of health.

Related info:

Lisa Oldson, MD

Dr. Oldson is Medical Director of the Analyte Physicians Group. She is on staff at Northwestern Memorial Hospital, as well as Clinical Instructor at the Feinberg School of Medicine, Northwestern University. Her areas of expertise include STDs (with a particular clinical emphasis on herpes), women's health, preventive medicine, diabetes, obesity and weight management, and mood and anxiety disorders. Dr. Oldson was educated at Rush Medical College and completed her residency at Rush-Presbyterian-St. Luke's Medical Center in Chicago, IL.

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