Background: Gestational diabetes mellitus (GDM) is typically diagnosed around 24–28 weeks of gestation but it is important to identify hyperglycaemia as early in pregnancy as possible, especially pregestational diabetes. While there is consensus on the cut-points of glucose for diagnosing pregestational diabetes, there is considerable debate on the cut-points for diagnosing GDM in the first trimester. Both prevalence data and effectiveness of managing GDM in the first trimester are lacking. 
Aim: The aim of this study was to look at the prevalence of GDM in the first trimester using the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) criteria among Asian Indian women. 
Methods: The participants in this study (n=570) were pregnant women screened as part of the STratification of Risk of Diabetes in Early pregnancy (STRiDE) project. Pregnant women reporting to four antenatal clinics in Chennai city in southern India, were recruited in early pregnancy (<16 weeks). Fasting plasma glucose (FPG) estimations was carried out (by hexokinase/kinetic method) in all eligible women before the end of 16 weeks of gestation. GDM was diagnosed using IADPSG criteria of FPG ≥92 mg/dl (≥5.1 mmol/L) and <126 mg/dl (7.0 mmol/L) and pregestational diabetes, if FPG ≥126 mg/dl (≥7.0 mmol/L).
 Results: The mean gestational age at time of fasting glucose testing was 11.6 ± 2.9 weeks. A total of 13.3% of women had hyperglycaemia [GDM–12.8% (73/570) and pregestational diabetes–0.5% (3/570)]. The baseline characteristics of women with and without GDM are shown in the Table. Women with GDM were significantly older, had higher BMI, waist circumference, percent body fat, systolic BP, diastolic BP, triceps and subscapular skinfold compared to non-GDM women. Previous history of GDM and family history of diabetes were significantly higher among women with GDM. GDM women had significantly higher venous and point-of-care HbA1c. Of those with GDM, majority had fasting glucose levels below the non-pregnant criteria for impaired fasting glucose (IFG) defined by ADA [<101 mg/dl (5.6 mmol/L); n=61/73; 83.6%] or NICE [<108 mg/dl (6.0 mmol/L); n=72/73; 98.6%].
Discussion: The prevalence of fasting hyperglycaemia is high even during the first trimester, in this Asian Indian population. This fits the IADPSG and ADA criteria for classifying them as GDM. This calls for earlier screening for GDM among high-risk ethnic groups like Asian Indians. However, the benefits of treating these women, particularly those below the threshold of IFG (92–100 or 108 mg/dl), are not known. It is also not known whether these women have higher 1 and 2-hour post-load glucose or higher total 24-hour glucose exposure. Given such high prevalence, studies that are designed to address these questions are urgently needed to reduce morbidity due to GDM.

High prevalence of gestational diabetes mellitus (GDM) in early pregnancy in Asian Indians – the STRiDE study