Objective

To describe a new measure, the unintended pregnancy risk index (UPRI), which is based primarily on attitudinal and behavioral measures of women's prospective pregnancy desire, and compare it to the unintended pregnancy rate, typically calculated retrospectively.

Study design

We used three rounds of the National Survey of Family Growth to calculate trends in the UPRI and compare it to the retrospective rate. The UPRI estimates the annual risk of becoming unintentionally pregnant, on a scale from 0 to 100. It is based on women's prospective pregnancy desire as well as fecundity, sexual activity and contraceptive use patterns.

Results

Among all women age 15–34, the UPRI ranged from 7.4 in 2002 to 5.7 in 2013. The retrospective unintended pregnancy rate had similar levels and declines for the same overall period, although the UPRI declined earlier than the retrospective rate.

Conclusions

Changes in the use of any contraceptive method, the methods used, and the effectiveness of the methods used all contributed to the decline in the UPRI.

Implications

The sufficiency of retrospective measures of pregnancy intention has been challenged and data availability has constrained needed surveillance of the unintended pregnancy rate. The UPRI offers a new measure that can be calculated with existing national surveillance data or for any population for which data on prospective pregnancy desire, pregnancy risk and contraceptive use are available.