The number of births to older mothers increased over the study period, almost doubling kinase inhibitor Tubacin for those aged 40 years and over. However, age-standardising had little effect on prevalence rates, and GDM prevalence increased

within most maternal age groups, indicating that rising maternal age does not fully explain the upward trends. GDM prevalence increased to a greater extent in pregnancies among Australian-born non-Indigenous women compared with rates in all overseas-born women. Consistent with existing knowledge,20 22 23 28–31 pregnancies occurring in women born throughout Asia and in North Africa and the Middle East had the highest GDM rates. Similar to recent reports of rising trends in GDM burden nationally20 and in the multiethnic state of New South Wales,3 23 we noted a pronounced increase in overall GDM prevalence in Victoria from 1999 to 2008. This may reflect secular increases in obesity prevalence in the general population36; effects of obesity could not be examined as maternal pre-pregnancy body mass index (BMI) was not recorded

in the VPDC during the study period. BMI trend data in Australian obstetric patients are sparse and generally from single centres. 37 Maternal BMI has been recorded in the VPDC since 2009; further research is required in the Australian context when population-level obstetric BMI trend data become available. In our study GDM prevalence increased across most maternal age groups. This and the fact that results were generally similar when restricting to primiparous women indicates that factors other than those examined in this study likely largely account for the observed trends. In the general Australian population, prevalence of overweight/obesity has

increased across most age groups over time38 and this may be contributing to the rising GDM prevalence observed in our study among most groups including the younger mothers. Rising GDM prevalence may also reflect increases in pre-existing but previously undiagnosed diabetes; as postnatal OGTT results were not available, the extent to which this is the case cannot be established. Additionally, GDM ascertainment may be influenced by systemic factors, which themselves may change over time. In particular, screening and diagnostic practices and uptake rates will influence case detection. For example, after introduction Cilengitide of universal OGTT testing in a regional hospital in northern Australia, testing rates in Indigenous Australian women increased from 31.4% in 2006 to 65.6% in 2008 and GDM rates tripled.26 This study has demonstrated that migrant disparities in GDM prevalence appear to be diminishing, but in a concerning rather than desirable manner: increases in GDM prevalence rates over time were most pronounced in Australian-born non-Indigenous women, among whom GDM prevalence was converging with the higher rates in overseas-born mothers.