Does Antenatal Risk Stratification Match Initial and Eventual Model of Care Allocation? A 5-Year Multi-Centre Review...

Every woman who books into a public hospital for antenatal care in Australia is assessed for risk factors for adverse outcomes. However, no study has examined empirical patterns of risk stratification, subsequent models of care and their relationship to perinatal outcomes.

This study aims to describe patterns of risk stratification and their intersection with allocated models of care and subsequent perinatal outcomes.

This is a multi-centre retrospective cohort study of all pregnancies booked in and delivered at the three maternity units in western Sydney between 1 January 2018 and 31 December 2022. Women were classified into one of three risk categories (A, B or C) as defined by the Australian College of Midwives' guideline. Variables measured include allocated models of care, maternal and fetal risk factors, birth outcome, and pregnancy morbidity and mortality.

At time of both booking-in and birth admission, most women were classified as Category C ('high risk'). During antenatal care, the number of women classified as Category C grew by 70.7% from 21,847 at booking in to 37,290 at birth admission. Between booking-in and admission for birth, there was an over 25% increase in women allocated to medical models of care during the study period. There was higher perinatal morbidity in women classified as 'high risk'.

Current antenatal risk stratification methods appear to detect women with a higher chance of adverse perinatal outcomes, but in doing so classify over three quarters of women as 'high-risk'. This has important ramifications for model of care, perceived patient risk, and resource allocation.