Effects of a Province-Wide Change in Gestational Diabetes Mellitus Screening Policy on Treatment and Newborn Birth Weight

OBJECTIVE To evaluate changes in gestational diabetes mellitus (GDM) treatment and newborn birth weight after a 2010 change in GDM screening recommendations from a two-step (50-g glucose challenge test + 3-h, 100-g oral glucose tolerance test [OGTT] with Carpenter-Coustan criteria) to a mix of one-step and two-step (2-h, 75-g OGTT with International Association for Diabetes in Pregnancy Study Group criteria). RESEARCH DESIGN AND METHODS We estimated effects of the screening change on the incidence of lifestyle or medication treatment, infant birth weight >90th percentile or <10th percentile for gestational age (large and small for gestational age), and endocrinologist visits using interrupted time series analysis in all 463,881 individuals with singleton pregnancies (>28 gestational weeks) from British Columbia, Canada, between 2004 and 2019. RESULTS After the screening change, lifestyle-treated GDM increased immediately (level change 1.85 [95% CI 1.19–2.51]), corresponding to a 1.85% increase in incidence. Medication-treated GDM increased gradually (trend change 0.23 [95% CI 0.09–0.37] per year), but there was no change in medication-treated GDM using a shorter (3-year) postpolicy period (level change −0.31 [95% CI −0.9 to 0.29]; trend change 0.03 [95% CI −0.36 to 0.43]). We detected no change in infant birth weight outcomes and endocrinology visits. CONCLUSIONS Changing the screening approach substantially increased diagnoses of lifestyle-treated GDM but did not impact medication-treated GDM or infant birth weight.