For pregnancies yielding more than one birth (ie, twins or more), only the birth record for the first-born infant was extracted. Each entry therefore represents one pregnancy. As women may have had more than one pregnancy selleck kinase inhibitor during the study period, the same woman may be represented in the data set multiple times. Variables used in this analysis were year of delivery, maternal age at delivery (categorised into age groups of ≤24 years, 25–29, 30–34, 35–39, ≥40 years), parity, diabetes status (GDM, pre-existing

maternal diabetes not further specified, no diabetes), maternal Aboriginal and Torres Strait Islander (ie, Indigenous) status and maternal country of birth. Maternal country of birth was reclassified into geographically-based regions using the Australian Bureau of Statistics’ Standard Australian Classification of Countries. This classification scheme includes Australia in the group Oceania and Antarctica. However, we categorised Australian-born women separately into two additional groups: Australian-born Indigenous and Australian-born non-Indigenous. Maternal diabetes status was assigned based on whether the clinician completing the notification form ticked the checkboxes for GDM or pre-existing maternal diabetes. Recording of GDM and pre-existing

diabetes in the VPDC are reported to be 99.4% and 99.8% accurate, respectively.35 Over the study period, Australian guidelines recommended universal offer of GDM screening, with selective screening of high-risk women considered appropriate in resource limited or low prevalence settings. Screening is performed at 26–28 weeks gestation and a positive result is a 1 h venous plasma glucose level

of ≥7.8 mmol/L after a morning, non-fasting 50 g glucose load or ≥8 mmol/L after a morning, non-fasting 75 g glucose load. Confirmation of GDM diagnosis after a positive screening test requires an OGTT at 26–30 weeks gestation with venous plasma glucose levels of ≥5.5 mmol/L at 0 h and/or ≥8 mmol/L at 2 h.5 Statistical analyses Maternal demographic GSK-3 characteristics over time were examined using descriptive statistics. Crude and age-standardised annual prevalence rates of pre-existing diabetes, GDM and all diabetes were calculated as a percentage of total annual pregnancies, using direct standardisation to the maternal age structure of the entire study population. GDM prevalence rates over time were further examined by maternal age group and region of birth. Small numbers precluded similar analyses for pre-existing diabetes. To examine the effect of denominator variation on overall GDM prevalence estimates, annual GDM prevalence rates were also calculated after excluding from the denominator pregnancies in women with pre-existing diabetes. Women who had more than one pregnancy during the study period were included in each year that they delivered.