Pearl Index and Contraceptive Safety

The „Pearl Index“ is the standard method used to assess the safety and effectiveness of different contraceptives. But what can this index tell us, how is it calculated and are these calculations really that reliable? We answer the most important questions about the Pearl Index here.

What is the Pearl Index?

The Pearl Index attempts to provide an assessment of the safety of a contraceptive method. It interprets the collected data of a specific contraceptive method to show how many out of 100 users became pregnant despite using the contraceptive within a year.

So, a Pearl Index of 2 indicates that 2 out of 100 women – despite using a specific contraceptive method – became pregnant within a year. This is also referred to as a ‚failure rate‘ of 2%.

It should be noted at this point that no contraceptive method has a Pearl Index of 0. In other words, regardless of which contraceptive method you choose, there is always a risk of becoming pregnant during intercourse. However, some contraceptive methods are significantly safer than others and can be compared based on the Pearl Index value. An overview of different methods and their safety according to the Pearl Index can be found below.

How is the Pearl Index calculated?

The lower the Pearl Index, the higher the protection of a contraceptive method. But how is the Pearl Index actually calculated?

The calculation is based on 1200 months of use (100 women over the course of one year) of a contraceptive method. The index determines how many of these 100 women became pregnant within a year while using the respective contraceptive method.

For example, it can be said: With a Pearl Index of 2, 2 out of 100 women became pregnant in one year. If the Pearl Index is, for example, 0.05, then one out of 2000 women became pregnant within a year.

Perfect Use vs. Typical Use

Even though the Pearl Index theoretically provides a good benchmark for comparability, it has a catch: its data mostly refers to the perfect use of a contraceptive method, also known as ‚method effectiveness.‘
In reality, however, there are many factors that can influence the perfect use of contraception, such as regular intake, drug interactions, the influence of illnesses, and general user errors.
To compare this everyday-like use of a contraceptive method as realistically as possible, the value of typical use (or ‚use effectiveness‘) should also be taken into account.

Pearl index for hormonal methods

Hormonal contraceptive methods include, for example, the contraceptive pill or the hormonal coil.

In 2023, the pill was replaced by the condom as the most commonly used contraceptive method for the first time. This is confirmed by a representative study by the Federal Centre for Health Education, in which sexually active men and women in Germany were asked about their contraceptive behavior: Only around 38% of those surveyed who use contraception stated that they or their partner use the pill. According to the Pearl Index, it has a failure rate of 0.3 – 1 %, making it one of the safest contraceptives when used correctly. However, this safety also comes at a high price, as the list of side effects is long: weight gain, thrombosis, hormonally induced mood changes, migraines and nausea are just some of the many possible side effects.

The pill also does not perform so well in typical use. This is because, for example, irregular use, drug interactions or gastrointestinal illnesses can significantly impair the effect of the hormone preparation.

The IUD is also a hormonal contraceptive. It is true that insertion by a gynecologist can prevent application errors and its typical use is therefore just as safe as the perfect application. However, due to the effect of synthetic hormones, significant side effects can also occur.

Incidentally, the widespread assumption that the contraceptive effect of the IUD or contraceptive ring is only „local“ is wrong:

The artificial hormones are released into the bloodstream via the mucous membrane and are thus distributed throughout the body.

Pearl index for natural methods

Unfortunately, there is a widespread assumption that natural contraception is very unsafe and really only suitable for family planning. The fact that natural contraception is generally perceived as very unsafe is unfortunately due to the prevalence of very unsafe methods such as the calendar method or coitus interruptus. As you can see from the failure rates of up to 22%, such methods are quite rightly frowned upon and not suitable for contraception.

However, safe and hormone-free contraception is definitely possible with the symptothermal method: it is the safest method of natural family planning and has a Pearl Index of 0.4 when used perfectly. Even with typical use, which includes user errors, it has a failure rate of just 1.8% and is therefore even safer than the pill. The method does not require any side effects, artificial hormones or copper.

Hormone-free contraception with trackle

The symptothermal method is based on certain calculation rules that have been researched and established by several independent studies. In order to use the symptothermal method safely and correctly, these rules must be applied and evaluated correctly.

And this is where trackle comes into play: The trackle cycle computer digitizes the symptothermal method and helps you to use it safely and easily. trackle is specially designed to avoid possible application errors when using the symptothermal method and makes the method extremely easy to use in everyday life: The sensor records and transmits the temperature data automatically and always applies the rules correctly.

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