Measuring Birth Outcomes: Validating the Perinatal Outcome Index
Patricia McNiven, RM, BScN, Msc, PhD Karyn Kaufman, RM, BSN, MS, DrPH Murray Enkin, MD, FRCSC, FACOG, LLD, Dsc
We undertook a study to assess the reliability and validity of a new measure of low risk maternity care. A Perinatal Outcome Index (POI), which combines intrapartum process of care and clinical outcome items into a summary index score, was originally developed and evaluated in the Netherlands. It was designed to measure the extent to which a labour and birth are "optimal", that is, one with minimal intervention resulting in a healthy mother and a healthy baby. We modified the Dutch index to make it applicable to a Canadian setting. A panel of experts who were not connected with the study reviewed the modified version for applicability, feasibility of obtaining data easily, and content validity. Data were abstracted from the health records of 324 women in one hospital and two midwifery practices to obtain Perinatal Outcome Index scores and examine aspects of construct validity. We measured the inter-rater reliability of the research assistants who abstracted information. The panel achieved consensus on all items in the modified Perinatal Outcome Index to establish content (face) validity. Labour and birth data were readily obtained from health records with high inter-rater reliability (Kappa 0.78). In a linear regression model, birth at home, multiparity, and having a midwife or family physician as a care provider were significantly associated with higher scores (having a more optimal birth) and accounted for 37% of the score variance. The Perinatal Outcome Index has satisfied our expectations for content and construct validity. Research assistants found it easy to use and data items were readily available from women's health records. Inter-rater reliability was acceptable. We believe the modified index will be useful for comparative studies among women at low or average risk, and for quality assurance programs.
perinatal outcome, outcome measures, low risk obstetrics, midwifery evaluation