Materials and methods
We analysed all women delivering at EH, both at Box Hill Hospital (BHH)
and Angliss Hospital (AH), between the 1st of July
2014 and the 30th of June 2019. Births included live
births and still births of at least 400 grams birthweight or at least 20
weeks of gestation. Both BHH and AH are teaching hospitals with
supervision and support from senior clinicians 24 hours and with theatre
availability. According to the capability framework for Victorian
maternities 12 BHH is a level 5 hospital with 2500
deliveries per year and AH is a level 4 hospital with 2200 deliveries
per year.
Data for all mothers and babies was collected retrospectively using the
Birthing Outcomes System (BOS), developed by Management Consultants and
Technology Services, in which information is routinely collected for all
women presenting to EH. BOS is a clinical information management system
integrating pregnancy and perinatal data which is widely used in
Victorian maternity services. Data in BOS was reviewed and extracted
following EH protocols (available on request). Data extracted included
all the variables needed to classify women into one of the ten Robson
groups. When additional information was required for clarifications full
medical records were reviewed.
To assess the quality and the coverage of our data, the obtained BOS
data was cross-referenced with the national birth registry to make sure
there were no missing cases. Additionally, as per the Robson
implementation manual 9 we compared the number of CS
and women in our data with the number of CS and women who delivered in
the hospital and lastly, we assessed the size and the CS rate of group 9
looking for misclassified cases.
As per the recommended Robson approach, the overall CS rate (percentage
of women delivered by CS), the size of each group, the CS rate per
group, and the absolute and relative contribution of each group to the
overall CS rate were calculated. We used linear regression to analyse
the trend of CS rate over time at BHH an, AH individually and EH as
whole. Additionally, we compared the trend between BHH and AH. A chi
square test was used to determine the differences between hospitals in
each of the Robson groups. Data were analysed in STATA 16.
This study was considered by the Office of Research and Ethics at EH
(reference QA19/097) and was deemed to have met the criteria for an
Audit or Quality Assurance activity, therefore as per the National
Health and Medical Research Council there was no requirement for Human
Research Ethics review.