A similar discrepancy is seen with the contraceptive pill. Its theoretical effectiveness is very high at 99.7 percent. However, a number of factors can reduce its effectiveness. For example, the pill is most effective after it’s been taken for seven consecutive days. Women who rely on the pill as their only contraceptive after taking it for just a few days are more likely to fall pregnant. Women are also more likely to fall pregnant if they forget a pill, take it at different times, or suffer from diarrhea. All these factors reduce its use-effectiveness to 91 percent.
However, in some cases, use-effectiveness can be the same as theoretical effectiveness. As hormonal implants like Implanon and Nexplanon are administered by trained doctors, they do not suffer the same level of human error. Therefore, their use-effectiveness is the same as their theoretical effectiveness: 99.95 percent.
Use-effectiveness rates typically get closer to theoretical effectiveness rates over time. That’s because with practice, people tend to become better at using their preferred contraception.
Use-effectiveness rates treat all conceptions that occur while using contraception equally, whether they result in a birth, an abortion, or a miscarriage.
While theoretical effectiveness gives you some idea about how well a contraception will work, it’s imperative to also consider the use-effectiveness. Assess your own lifestyle and habits to decide whether your contraceptive’s effectiveness rate is more likely to be closer to the theoretical effectiveness or use-effectiveness rate. If you feel concerned about how effectively a contraceptive is likely to work for you, you may like to use an alternative method, either on its own or in conjunction with your preferred choice.