Effects of a province-wide change in gestational diabetes screening policy on treatment and newborn birth weight

OBJECTIVE: To evaluate changes in GDM treatment and newborn birthweight after a 2010 change in GDM screening recommendations from a 2-step (50-g glucose challenge + 3-h 100-g oral glucose tolerance test (OGTT) with Carpenter-Coustan criteria) to a mix of 1-step and 2-step (2-h 75-g OGTT with IADPSG criteria).

RESEARCH DESIGN AND METHODS: We estimated effects of the screening change on the incidence of lifestyle or medication treatment, infant birth weight greater than the 90th percentile or less than the 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 to 2.51) corresponding to an immediate 1.85% increase in incidence. Medication-treated GDM increased gradually (trend change 0.23 95% 0.09 to 0.37 per year), but there was no change in medication-treated GDM using a shorter (3 year) post-policy (level change: -0.31 (-0.9, 0.29); trend change: 0.03 (-0.36, 0.43)). We detected no change in infant birth weight outcomes and endocrinology visits.

CONCLUSIONS: Changing screening approach substantially increased diagnoses of lifestyle-treated GDM, but did not impact medication-treated GDM or infant birth weight.