2148-P: Subtyping Early GDM: Insulin-Resistant Early GDM Predicts Worse Pregnancy Outcomes but Benefits Most from Early Treatment

Introduction and Objective: Insulin-resistant late Gestational Diabetes Mellitus (IR-lGDM) is associated with worse pregnancy outcomes. We compared pregnancy outcomes and treatment effect between women with IR-early GDM (IR-eGDM), non-IR-eGDM and normal glucose tolerance (NGT). Methods: Pregnant women with GDM-risk factors enrolled in a multicenter RCT performed a 75g early OGTT (eOGTT) 20 wks, with fasting serum insulin, and 24-28 wk OGTT if no GDM on eOGTT (IADPSG criteria). IR-eGDM was defined by Homeostatic Model Assessment (HOMA)-IR 75th percentile from women with NGT, all other eGDM were classified as non-IR-eGDM. Each eGDM subtype was compared to NGT for outcomes and early treatment effect using multiple logistic regression, calculated with adjusted odds ratios (aOR(95% CI)). Results: Among 488 women with eGDM, median(IQR) HOMA-IR was 2.52(1.65-3.76): 322 (66%) had IR-eGDM using NGT (N=403) HOMA-IR 75th centile threshold of 1.998. For IR-eGDM vs non-IR-eGDM, pre-pregnancy BMI, OGTT fasting glucose and European ethnicity respectively were higher, while gestational weight gain was lower (all p≤0.001). Relative to women with NGT, early treated IR-eGDM (N=164) was associated with higher odds of hyperbilirubinemia requiring phototherapy (2.65(1.40-5.03)) and NICU admission (1.77(1.07-2.91)). Delayed treatment IR-eGDM (N=158) was also associated with higher odds of hyperbilirubinemia requiring phototherapy and NICU admission, as well as the neonatal adverse outcome composite (1.93(1.19-3.22)) and respiratory distress (2.30(1.25-4.21)). Non-IR-eGDM had similar outcomes to NGT, irrespective of treatment timing. Conclusion: Women with IR-eGDM have a higher risk of neonatal complications, several of which are attenuated with early treatment. Those with non-IR-eGDM have similar outcomes to women with NGT. Disclosure A. Sweeting: None. M. Hivert: None. J. Immanuel: None. A.A. Hardikar: None. N. Pham: None. W.M. Hague: None. M.J. Peek: None. V.W. Wong: None. E. Gianatti: None. A. Kautzky-Willer: None. J. Harreiter: None. H.E. Backman: None. V. Mohan: None. C. Nolan: None. D. Simmons: Speaker's Bureau; Ended; Novo Nordisk. Other - Educational grant; Ended; Abbott Diabetes. Research Support; Current; Novo Nordisk. Consultant; Ended; Dexcom, Inc. Funding NHMRC (grants 1104231 and 2009326); Region Örebro Research Committee DnrOLL-970566, OLL-942177; Medical Scientific Fund of the Mayor of Vienna, project 15205; SouthWestern Sydney Local Health District Academic Unit grant 2016; Western Sydney University AinsworthTrust grant 2019; Australia-Harvard Fellowship 2025