Birth Control Effectiveness: Different Types and How It's Measured
Birth control affects many of us throughout our lifetimes. One thing that’s important to consider when choosing birth control is the effectiveness of the method. In this article, we’ll take a look into the ways birth control effectiveness is worked out, how it’s measured, and how your birth control can teach you more about your body. No birth control is 100% effective. Whatever method you choose to use, there will still be a risk of pregnancy. However, some birth control methods are more effective than others, and the good news is that using birth control can significantly reduce the risk of getting pregnant.
How can we measure birth control effectiveness?
Every one of us is different and will have a different experience with birth control. However, it’s important we have a clinical measurement when we talk about birth control effectiveness so we can understand how well a method works for a larger number of people. In the contraceptive landscape, we normally talk about two measures of effectiveness called typical use and perfect use.
What is typical use?
Typical use reflects how birth control is used by real people in real life. As well as method failure, typical use also incorporates user error. This includes:
- The method being correctly used every time the couple have sex
- The method is correctly used, but not used every time a couple has sex
- The method is used, but sometimes incorrectly
- The method is used incorrectly or is forgotten to be used
As you can see, typical use provides room for error - hence why the failure rate is usually higher than perfect use. This is particularly true for methods that require work from the user.
What is perfect use?
Without taking into account user error, perfect use looks at the method’s effectiveness in a perfect world — i.e. if it was used exactly as it was intended every time a couple had sex. There is still a failure rate that applies if the method itself should stop working, but perfect use tends to be higher than typical use as it removes user error completely.
The Pearl Index
The Pearl Index is defined as the number of pregnancies that would happen for one method per 100 women over a year. The pearl index is easy to calculate and understand, and it can be computed for both typical use and perfect use. This calculation allows providers to understand how effective a contraceptive method is at preventing pregnancies with real-world use.
Comparison of Common Birth Control Methods
Below is a summary of effectiveness data for common methods based on the Pearl Index and usage types:
- Male Condoms: These have a typical use of birth control effectiveness of 87% and a perfect use effectiveness of 98%.
- Birth Control Pill: This method has a typical use effectiveness of 93% and a Pearl Index of 7 (meaning seven women in one year are expected to get pregnant while using the pill).
- Natural Cycles: This is a non-invasive, non-hormonal form of birth control that uses basal body temperature data and period data to calculate daily fertility status.
Method Characteristics and Client Autonomy
To address client autonomy, contraceptive methods are often grouped into categories based on how they are started or stopped. Methods are generally listed in order of effectiveness within these frameworks:
- Self-managed: Clients can start and stop on their own.
- Prescription-based: Requires provider to start with a prescription, but clients can stop on their own.
- Reversible procedures: Requires provider for clients to start and stop.
- Permanent methods: Requires provider to perform a procedure.
- Emergency contraception: Used after unprotected intercourse.
It is important to note that the most autonomous methods often require more frequent use, while the least autonomous methods (those requiring a provider) are frequently the most effective and easiest to use.