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Measuring Outcomes of Midwifery Care: The Optimality Index-US

The vast majority of births in the United States (US) are to mothers with few health problems or complications. However, most instruments used to assess birth outcomes are based on assessments of risk and counting adverse outcomes. As these are uncommon events in most births, research on the process and outcomes of birth to essentially healthy women becomes difficult. An innovative measurement instrument (the Optimality Index-US) has been developed to be sensitive to these differences. The Optimality Index-US (OI-US) is unique in that it shifts the measurement focus from adverse to good outcomes, and counts the frequency of “optimal” events during childbirth.

Defining outcomes in terms of the frequency of optimal events (the positive perception) rather than the occurrence of adverse events (the negative view) also allows for incorporation of a non-interventive philosophy in the measurement instrument. The “optimality” score is lowered by increasing interventions in normal processes. This makes the instrument an ideal approach to studies involving midwifery care, as it is based on one of the hallmarks of midwifery philosophy: the "advocacy of non-intervention in the absence of complications."  

The concept of “optimality” in perinatal research has its origins in the 1960s in the work of Prechtl (1968, 1980) who first described an “optimality principle” conceived for identifying infants with a “perfect start in life.” The basis for this principle was that mothers should be in perfect health and that pregnancy and childbirth should have evidenced no problems. In addition, the principle involved an underlying assumption that any interventions during pregnancy or labor would therefore indicate a problem, and result in a failure to meet the “optimal” criterion. This concept was later adapted by Wiegers as an approach to measuring the quality of midwifery care in the Netherlands (Wiegers, 1996). She developed a tool to measure “maximum outcome with minimal intervention”, and tested it among women in the Netherlands (Weigers, 1996).

Murphy and Fullerton (2001) adapted this tool for use in the United States and published a paper describing the development of the instrument for use in the US. The Optimality Working Group (OWG), a coalition of midwifery researchers interested in the concept, have conducted a series of studies in a variety of geographic settings and among women of diverse demographic profiles, each of which showed that the instrument demonstrated the ability to distinguish between groups of essentially healthy women in the various studies.

The Optimality Index-US is freely available at the website. However, the tool is a copyrighted instrument. Individuals who use the tool must give full source attribution. Users should download the current versions of the Users Guide (August 2012), the measurement tool (August 2012) and the codebook (August 2012.). The bibliography contains full reference citations for each item presented in the instrument. The publications file contains a list of articles about development and psychometric properties of the OI-US. Data collection tools that have been developed, tested and refined by researchers in other studies, and that may prove useful in other applications are also available.

Meetings of the Optimality Working Group are held at the ACNM annual meeting, and those interested in the concept are welcome to attend. We welcome your questions and your feedback.





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