Impact of using fasting plasma glucose and HbA1c instead of OGTT as a screening tool for gestational diabetes: a retrospective study

Aims: To examine the impact of using the Royal College of Obstetricians and Gynaecologists (RCOG) COVID-19 Gestational Diabetes (GDM) criteria on identifying women with GDM. Methods: Data were collected between November 2018 and June 2019, from women previously diagnosed with GDM using NICE guidelines, who also had HbA1c data available. These were used to determine whether they would have been diagnosed had the RCOG criteria been applied. Data were also collected to compare birth and fetal outcomes, and to compare medical management. Results: Eighty-nine women were included; 43 (48%) met both the RCOG and NICE GDM diagnostic criteria (RCOG + NICE group), while 46 (52%) only met the NICE GDM criteria and would have been missed using the RCOG GDM criteria (NICE only group). There were no significant differences in outcomes between the groups in terms of neonatal and delivery complications. More women in the RCOG + NICE group required treatment with insulin (11 [25.6%] vs 1 [2.2%], p=0.0010) or metformin (23 [53.5%] vs 14 [30.4%], p=0.03). Conclusions: Applying the RCOG criteria resulted in approximately half of women previously diagnosed with GDM to be missed, one-third of whom had severe insulin resistance requiring treatment with metformin or insulin. The retrospective design of this study may not represent the neonatal and delivery outcomes these women may have had if their diagnosis had been missed. Women should be informed about this risk when not offered an oral glucose tolerance test to guide decision making. Copyright (c) 2023 John Wiley & Sons.