Predictors for insulin use in gestational diabetes mellitus

Objectives: Gestational diabetes mellitus (GDM) affects about 15% of pregnancies in Australia, with approxi-mately 30% of those diagnosed with GDM requiring insulin therapy. There are several established risk factors for developing GDM, however limited studies show how these can be used to predict need for insulin treatment. The aim of this study is to identify predictors of insulin therapy in women diagnosed with GDM once an oral glucose tolerance test (OGTT) is performed during pregnancy.Study design: This is a retrospective cohort study of women with singleton pregnancies complicated by GDM between 2016 and 2017 at a single, large health network in Melbourne, Australia. Data were obtained from hospital record and pathology result systems. Univariable and multivariable logistic regression models were fit to the data to obtain crude and adjusted odds ratios.Results: Of 2,048 women diagnosed with GDM, 647 (31.6%) required insulin therapy. Positive predictors included in the final multivariable model after backwards, stepwise elimination were an elevated fasting result on an OGTT (adjusted odds ratio (AOR) 2.93 [95% CI 2.34-3.66]), previous birth weight greater than 90th% (AOR 2.04 [95% CI 1.412.94]), previous diagnosis of GDM (AOR 1.68 [95% CI 1.28-2.21]), being born in the South Asian region (AOR 1.58 [95% CI 1.27-1.98]), the 2hr OGTT result (AOR 1.14 [95% CI 1.05-1.24]), body mass index (BMI; AOR 1.13 [95% CI 1.04-1.23]) and age (AOR 1.03 [95% CI 1.00-1.05]) The final predictive model had an area under the receiver-operating characteristics (ROC) curve of 0.744 (95% CI 0.720-0.767).Conclusions: This study highlights the possible predictors of insulin use, informing counselling for women who are newly diagnosed with gestational diabetes.