Fasting Glucose for the Diagnosis of Gestational Diabetes Mellitus (GDM) during the COVID-19 Pandemic

Background: During the COVID-19 pandemic, different non-validated tests were proposed to simplify the diagnosis of gestational diabetes (GDM). Aim: To analyse the effects of replacing the two-step approach for Early-GDM and GDM diagnosis, with a fasting plasma glucose test. Material and Methods: This is a cohort study consisting of 3200 pregnant women: 400 with Early-GDM, 800 with GDM and 2000 with Non-GDM diagnosed using the two-step approach. Using fasting plasma glucose for Early-GDM and GDM diagnosis, according to the recommendations of Spain, Australia, Italy and the UK during the pandemic, the rates of missed and new Early-GDM and GDM were calculated and perinatal outcomes were analysed. Results: Using fasting plasma glucose in the first trimester >100 mg/dL for Early-GDM diagnosis, the rates of post-COVID missed and new Early-GDM were 79.5% and 3.2%, respectively. Using fasting plasma glucose at 24–28 weeks <84 or >92, 95 or 100 mg/dL for GDM diagnosis, the rates of missed GDM were 50.4%, 78%, 82.6% and 92.4%, respectively, and 8.6%, 5.6% and 2.3% women with Non-GDM were diagnosed with new GDM. Conclusion: Fasting plasma glucose is not a good test for the diagnosis of GDM either in the first trimester or at 24–28 weeks.