How many birth control pills do women really miss a month?

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.