Contraception

Pearl Index

AlsoPearl ratecontraceptive failure rate per 100 women

Not yet reviewed by a clinician. This health entry was written from the public-health sources listed below and is general information only. It is not medical advice.

Definition

The Pearl Index is a measure of contraceptive failure: the number of pregnancies per 100 women using a method for one year of exposure.

At a glance

  • It counts pregnancies per 100 women using a method for one year of exposure.
  • A lower number means a more effective method.
  • It is named after the biologist Raymond Pearl, who proposed it in the 1930s.
  • It assumes failure risk stays the same over time, which is often not true.
  • Researchers also use life-table analysis alongside it.

In detail

Named after the biologist Raymond Pearl, who proposed it in the 1930s, it is still commonly reported in clinical trials and on product leaflets. A lower number means fewer pregnancies and a more effective method.

It has limitations: it assumes the risk of failure stays the same over time, when in reality failure is often higher in the first months of use. Researchers therefore also use life-table analysis, and public information more often talks about typical-use and perfect-use percentages.

In a sentence

  • The product leaflet listed the Pearl Index from the clinical trials.
  • Our lecturer explained why the Pearl Index can be misleading for long studies.

Where the word comes from

Named after the American biologist Raymond Pearl, who proposed the measure in the 1930s.

Not to be confused with

  • Typical use

    Typical use is a way of describing real-life effectiveness, whichever statistic is used.

Common questions

What does a Pearl Index of 1 mean?

It means roughly one pregnancy per 100 women using the method for a year of exposure. Lower numbers mean fewer pregnancies.

Why is the Pearl Index criticised?

It assumes the risk of failure stays the same over time, when in reality failure is often higher in the first months of use. Public information more often uses typical-use and perfect-use percentages.

Related terms

Sources

  1. Contraception (peer-reviewed)Contraceptive failure in the United States