Measurement of Perinatal Outcomes: A Decade of Experience and a Future Vision for the Optimality Index-US

The Optimality Index-US (OI-US) is a research instrument that was developed for the purpose of measuring aggregate perinatal care processes and outcomes against an optimal or best possible standard. The index is based on the premise that obstetric intervention reflects a deviation from optimal physiologic childbirth. The instrument is continually reevaluated to ensure that it is grounded in contemporary evidence of "best practice." The value of the OI-US in distinguishing and comparing processes and outcomes of care across and within various clinical situations has been demonstrated in published literature. This article recaps the 10-year experience of instrument development and presents essential information derived from several studies of its psychometric and clinimetric properties. Findings from researchers who have used the original or adapted instrument in various geographic settings and populations are recounted. The article reviews the strengths and limitations of the instrument, and proposes next steps for researchers and clinicians to consider in the evolution and adaptation of the index for use on a global scale.