Prevalence and Timing of Screening and Diagnostic Testing for Gestational Diabetes Mellitus: A Population-Based Study in Alberta, Canada

OBJECTIVE The extent to which pregnant women are screened for gestational diabetes mellitus (GDM) at the population level is not known. We examined the rate, type, and timing of GDM screening and diagnostic testing in the province of Alberta, Canada. Geographic and temporal differences in screening rates, and maternal risk factors associated with lower likelihood of screening, were also determined. RESEARCH DESIGN AND METHODS Our retrospective linked-database cohort study included 86,842 primiparous women with deliveries between 1 October 2008 and 31 December 2012. Multivariable logistic regression analysis was used to examine maternal factors associated with lower likelihood of GDM screening. RESULTS Overall, 94% (n = 81,304) of women underwent some form of glycemic assessment in the 270 days prior to delivery. The majority (91%) received a 50-g glucose screen (GDS). Women not screened were younger and more likely to smoke and had lower maternal weight and median household income. When a diagnostic 75-g oral glucose tolerance test (OGTT) was indicated, it occurred a median of 10 (interquartile range 7, 15) days after the screen. CONCLUSIONS GDS occurred widely in a system where it was universally recommended and paid for publicly. When indicated, a 75-g OGTT was completed within 15 days in 75% of cases. Our finding that this two-step approach was widely implemented in a timely fashion supports continued endorsement of a two-step approach to screening and diagnosis of GDM. Further research is merited to assess whether the one-step GDM diagnostic approach results in different rates and timing of the 75-g OGTT and affects pregnancy outcomes.