Limitations:
There are limitations to this study. We have not included data from other public and private hospitals in the ACT and NSW surrounds. The ACT and surrounding areas do not have a centrally linked birthing data collection system, so it was difficult to access this information. CHWC is the sole tertiary level hospital for high risk women for ACT and NSW surrounds so it is likely that most high-risk cases were referred to CHWC, however, including trends from other hospitals would strengthen the results. In addition, the study did not include mid trimester losses prior to 20 weeks as the Birth Outcomes System at the CHWC does not record births prior to this period. We also did not include births beyond 39 weeks. This information may be useful when analysing PTB trends and patterns and would further strengthen the study’s results. Lastly, the study was conducted in a well-resourced country and different health systems and societies may require different approaches.