Background: Typically, gestational diabetes mellitus (GDM) is diagnosed between 24-28 weeks (called conventional GDM; cGDM for this study). However, hyperglycemia can be present in the first trimester of pregnancy (called early pregnancy GDM; eGDM for this study) and if left undetected could result in adverse outcomes in pregnancy and adverse metabolic programming of the offspring.(1-4) However, the exact prevalence of eGDM and the risk factors are not known even in high-risk populations such as India.
Aim: To estimate prevalence of eGDM, its risk factors and to compare them with cGDM
Methods: The STratification of Risk of Diabetes in Early pregnancy (STRiDE) study recruited pregnant women during first trimester from seven antenatal clinics in south India. Overall, 2,703 women underwent fasting plasma glucose (FPG) screening before 16 weeks of gestation. Based on International Association for Diabetes in Pregnancy Study Group (IADPSG) FPG criteria, (5) the women were categorised as follows: FPG ≥7.0 mmol/L- overt diabetes, FPG between 5.1 and 6.9 mmol/L – eGDM, FPG <5.1 mmol/L - screened again at 24-28 weeks by IADPSG criteria to classify cGDM and normal glucose tolerance (NGT). Women categorised as eGDM, cGDM and NGT were included in the analysis. Binary logistic regression models were built to assess the risk factors for eGDM and cGDM compared to NGT group.
Findings: The prevalence of eGDM was 21.5% (n=566). Of these 566 women, 16.3% had FPG levels ≥5.6mmol/l (American Diabetes Association criteria) and 5.8% had FPG levels ≥6.0mmol/l (National Institute of Health Care Excellence criteria). The prevalence of cGDM was 19.5%. The eGDM group had significantly higher early pregnancy weight (64 vs. 61 kg), BMI (26 vs. 25 kg/m2), HbA1c (5.3% vs. 5.1%) and previous history of GDM (8.5% vs. 5.3%) compared to the cGDM group. Elevated early pregnancy HbA1c (OR: 5.410, 95% CI: 3.930 - 7.447, p <0.001), high BMI (OR:1.056, 95% CI:1.032 - 1.081, p <0.001), and history of GDM (OR:1.894, 95% CI: 1.216 - 2.950, p 0.005) in previous pregnancy were identified as eGDM risk factors. For cGDM the risk factors were older age, elevated early pregnancy HbA1c, family history of diabetes, and family history of GDM.
Conclusion: There is a high prevalence of eGDM among south Asian Indian women, which highlights the need for screening for GDM in the first trimester. Modifiable risk factors like early pregnancy BMI and HbA1c may play a vital role in prepregnancy planning in such high-risk women.