While oral contraceptives (birth control pills) remain the most popular reversible method of contraception in the United States, incorrect use is unfortunately common. In fact, one million unintended pregnancies occur every year from pill user failure.

Unintended.mistimed pregnancies are a serious health issue in the United States. The public cost is more than $11 billion a year for the medical care during pregnancy and care of the infant for the 1rst year of life. Other hidden costs of unintended pregnancies include adverse pregnancy outcomes, and lower educational attainment of these children in their teen years. If the pregnant mother is a teen, the socioeconomic ramifications are even greater. In addition, 40% of unintended pregnancies end in abortion. Fifty-four percent of women seeking an abortion indicate they were using a contraceptive method in the cycle they got pregnant.

As most contraceptives have a typical failure rate of less than 17% the typical use must be either A) worse that we thought B) people don’t realize/admit they are using their method incorrectly.

A study using electronic pill packages that recorded when pills were actually taken versus diary (self-reported pill use) tells us that both hypotheses appear to be true (Hou et al. Obstet Gynecol 2010;116). This study was designed to evaluate the efficacy of daily text messages on correct pill use, but as all participants self-reported pill use in addition to electronic monitoring with specialized packages there is interesting information on how women actually took the pill versus how they reported taking the pill.

The average age of women in the study was 22 years and 99% were high school graduates. The average number of missed pills per month (over three months) as reported by the electronic device was 4.7 (yes, you read that correctly), however, study participants recorded missing only one pill a month in their diaries. Almost a four pill per month discrepancy.

Despite the rather poor pill taking behavior, there were no pregnancies during the three months of the study. The 79 women with complete electronic information (adequate sample size for the study) followed for three months is not adequate to test pill efficacy (under powered for that outcome measure and follow-up is typically 12 months). In addition, 78% of the women reported using condoms at least 50% of the time so many were using a back-up method.

What’s most interesting about this study is that 91% of the women reported anxiety about getting pregnant, strongly agreeing with the statement, “I would be upset if I were to get pregnant right now.”

This study may not be applicable for every woman as it studied a primarily white, high school educated demographic with an average age of 22 years. However, given the number of unplanned pregnancies among pill takers, I suspect it is applicable to many women outside of the study demographic. It is hard to believe that adolescent pill takers would be better.

Missed pills are far more common than we think and more common that pill-takers admit (this may not be conscious…remember, dieters who don’t journal eat about 1,000 calories a day more than they think, it seems to be human nature to give ourselves the benefit of the doubt). However, this electronically accurate view of pill taking helps us understand how so many oral contraceptive users end up with an unplanned pregnancies.

Real life oral contraceptive pill use is a very important point of discussion, not only in the doctor’s office but between every sexually active heterosexual couple and for every parent who may have a sexually active adolescent, because being on “the pill” may simply not be enough.

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  1. I took a cyproteronacetate pill for over 20 years, right up to menopause.
    Still have to take hypertension pills (differing ones, have now found a combination that works).
    To take 1 per month not at all, and 2-3 some hours too late seems quite right – and I thought I was especially forgetful!!!!
    Glad to be just average.

  2. This is one of the key reasons that long acting reversible contraceptives like IUD’s and implants are becoming so much more popular. Not only do you end up with way less hormone in your body, they take forgetting (and fights and finances) out of the day-to-day equation. With a settled in hormone-free copper IUD, the annual pregnancy rate is below 1 in 500; with a hormonal iud it’s 1 in 800, and with an implant it’s below 1 in 2000. Especially for teens, who are even worse than young adults at pill taking, that’s a total game changer.

  3. Well as its a good platform to get information about sex and outcomes of unsafe sex i.e., without condom. But you should seek some knowledge about safe sex and also how to get most out of it. You may visit for this purpose http://www.ambrina.com or Click Here

  4. It would be interesting to know how these numbers compare to, say chemotherapy medications or antibiotics.

  5. that is one reason I have never relied on bcps for birth control. I know I’m a terrible pill taker. My mother has nagged me for the past 20 years to get on the pill. Never have and no unplanned pregnancies either.

  6. I think this is a really clever way to test the accuracy of self reporting.

    However, I did have one question: How did the authors define a “missed” pill? Maybe the participants had a more lenient (and wrong) definition of a missed pill than the investigators.

  7. Does “missed pills” include those taken later in the day? So if a woman usually takes her pill between 7 and 8 am, but forgets one morning and then realizes in the evening that she forgot and takes it then, did the electronic pill packages record that as a missed pill? Would that account for some of the discrepancy, or did the study address that?

    Loren, my pills come in Sunday-start packs, so it’s very easy for me to see if I’ve missed a pill since each one is labeled with a day of the week.

  8. I’m not one bit surprised that the number of actual missed pills exceeds what the women reported. I would be surprised if it were any other way. For her to know she missed a pill requires both that she forget it and then later remember that she forgot it. However, if she simply forgets it it will be a missed pill but she won’t know it.

    I would think they could improve the track record by changing how the pill is produced. Produce four versions of packs of birth control pills that contain 28, 29, 30 & 31 pills. The cyclic versions would contain extra real pills and would extend her cycle for that month. The pharmacist would dispense packs that match up with the months that way you can always tell by looking at the pack whether you missed a pill or not.

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