Effects of implementing a routine postpartum fasting blood glucose on the completion of the gold standard 2-hour oral glucose tolerance test in gestational diabetics.

OBJECTIVE: Rates of completion of the gold standard 2-hour oral glucose tolerance test (OGTT) for impaired glucose intolerance postpartum in patients with gestational diabetes mellitus (GDM) are consistently less than 50 percent. Screening tests performed prior to hospital discharge, including a fasting blood glucose (FBG) to detect persistent hyperglycemia, have been investigated. We lack evidence, however, on whether implementation of routine postpartum FBG impacts the likelihood of obtaining the routine 2-hour OGTT. We sought to retrospectively compare the rates of completion of the 2-hour OGTT pre- and post-implementation of a routine FBG screen.

STUDY DESIGN: We performed a single-center retrospective cohort study comparing the completion of the 2-hour OGTT pre- and post-implementation of a routine FBG screen. Our primary outcome was completion of the postpartum OGTT. Bivariate analyses assessed associations of demographic and pre-induction clinical characteristics by pre- and post-implementation groups, as well as OGTT completion. Multivariable logistic regression was used to control for possible confounders. A sensitivity analysis was performed to account for the overlap with the COVID pandemic.

RESULTS: 468 patients met inclusion and exclusion criteria. In our post-intervention group, 64% of patients completed a postpartum FBG. For our primary outcome, completion of the 2-hour OGTT significantly decreased in our post-intervention group from 37.1% to 25.9% (p=0.009), aOR 0.62 CI[0.41 - 0.92]. This difference was no longer statistically significant when excluding patients during the pandemic, from 40.3% to 33.1% (p=0.228), aOR 0.76 CI[0.455 - 1.27].

CONCLUSIONS: Implementation of a routine FBG was associated with a negative impact on patients completing a 2-hour OGTT. The difference was no longer significant when excluding patients who would have obtained the OGTT during the pandemic, which may have been due to the smaller cohort. Future work should investigate patient perceptions of the FBG and its impact on their decision-making around the OGTT.