Comment: The quality of evidence is upgraded by large magnitude of effect.
In a population-based, retrospective cohort study 1 15,381 women referred for an antepartum oral glucose tolerance test (OGTT) indicative of an abnormal 50-g glucose challenge test (GCT), but without GDM, were matched (for age, region, socioeconomic status, and year of delivery) with up to 4 other women without such referral (n = 61,237). The two cohorts were followed over a median 6.4 years for the development of diabetes. The rate of incident DM was 5.04 cases per 1000 person-years in the cohort of women who underwent an antepartum OGTT, compared with 1.74 cases per 1000 person-years in women without an OGTT. The hazard ratio for subsequent DM in women with abnormal GCT was 2.56 (95% CI 2.28 to 2.87, P < 0.0001).
A cross-sectional study 2 determined the proportion of women who progress to type 2 diabetes mellitus (T2DM) and associated risk factors 5 to 6 years after hyperglycaemia first detected in pregnancy (includes GDM) in Cape Town, South Africa. Each participant had a 75 g OGTT; anthropometric measurements and a survey were administered. Mean age was 37.2 years (SD 6.0). Of the 498 participants 220 were followed-up for 5 – 6 years. 48 % (95% CI 41.2 to 54.4) progressed to T2DM, 5.5% (95% CI 3.1 to 9.4) had impaired fasting glucose, and 10.5% (95% CI 7.0 to 15.3) had impaired glucose tolerance. When GDM was categorized post hoc according to WHO 2013 guidelines, progression in the diabetes in pregnancy group was 81% (95% CI 70.2 to 89.0) and 31.3% (95% CI 24.4 to 39.3) in the GDM category. Factors associated with risk of progression to T2DM were; waist circumference (odds ratios [OR] 1.1, 95% CI 1.0 to 1.1, p = 0.007), hip circumference (OR 0.9, 95% CI 0.8 to 1.0, p = 0.001), and BMI (OR 1.1, 95% CI 1.0 to1.3, p = 0.001), and at baseline: insulin (OR 25.8, 95% CI 3.9 to 171.4, p = 0.001) and oral hypoglycaemic treatment during HFDP (OR 4.1, 95% CI 1.3 to 12.9, p = 0.018), fasting (OR 2.7, 95% CI 1.5 to 4.8, p = 0.001), and oral glucose tolerance test 2-hour glucose concentration at HFDP diagnosis (OR 4.3, 95% CI 2.4 to 7.7, p < 0.001). There was no control group.
1. Retnakaran R, Shah BR. Abnormal screening glucose challenge test in pregnancy and future risk of diabetes in young women. Diabet Med 2009;26(5):474-7. [PMID:19646185]
2. Chivese T, Norris SA, Levitt NS. Progression to type 2 diabetes mellitus and associated risk factors after hyperglycemia first detected in pregnancy: A cross-sectional study in Cape Town, South Africa. PLoS Med 2019;16(9):e1002865. [PMID:31498800]
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