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

Abstract

Background: Global data indicate that women with a history of hyperglycemia first detected in pregnancy (HFDP) are at up to 7 times risk of progressing to type 2 diabetes mellitus (T2DM) compared with their counterparts who have pregnancies that are not complicated by hyperglycemia. However, there are no data from the sub-Saharan African region, which has the highest projected rise in diabetes prevalence globally. The aim of this study was to determine the proportion of women who progress to T2DM and associated risk factors 5 to 6 years after HFDP in Cape Town, South Africa.

Methods and findings: All women with HFDP, at a major referral hospital in Cape Town, were followed up 5 to 6 years later using a cross-sectional study. Each participant had a 75 g oral glucose tolerance test; anthropometric measurements and a survey were administered. A total of 220 participants were followed up. At this time, their mean age was 37.2 years (SD 6.0). Forty-eight percent (95% CI 41.2-54.4) progressed to T2DM, 5.5% (95% CI 3.1-9.4) had impaired fasting glucose, and 10.5% (95% CI 7.0-15.3) had impaired glucose tolerance. Of the participants who progressed to T2DM, 47% were unaware of their diabetes status. When HFDP was categorized post hoc according to WHO 2013 guidelines, progression in the diabetes in pregnancy (DIP) group was 81% (95% CI 70.2-89.0) and 31.3% (95% CI 24.4-39.3) in the gestational diabetes mellitus (GDM) category. Factors associated with risk of progression to T2DM were; at follow-up: waist circumference (odds ratios [OR] 1.1, 95% CI 1.0-1.1, p = 0.007), hip circumference (OR 0.9, 95% CI 0.8-1.0, p = 0.001), and BMI (OR 1.1, 95% CI 1.0-1.3, p = 0.001), and at baseline: insulin (OR 25.8, 95% CI 3.9-171.4, p = 0.001) and oral hypoglycaemic treatment during HFDP (OR 4.1, 95% CI 1.3-12.9, p = 0.018), fasting (OR 2.7, 95% CI 1.5-4.8, p = 0.001), and oral glucose tolerance test 2-hour glucose concentration at HFDP diagnosis (OR 4.3, 95% CI 2.4-7.7, p < 0.001). Our findings have limitations in that we did not include a control group of women without a history of HFDP.

Conclusions: The progression to T2DM in women with previous HFDP found in this study highlights the need for interventions to delay or prevent progression to T2DM after HFDP. In addition, interventions to prevent HFDP may also contribute to reducing the risk of T2DM.

Fig 1. Flow chart of the study.

CVD, cardiovascular disease.

Fig 2. Progression to T2DM by the modified WHO 2013 criteria for GDM.

*GDM depicts women who would be categorized as GDM under the WHO 2013 GDM criteria, but this cohort had slightly different cut-offs (fasting glucose between 5.6 and 6.9 mmol/L and/or 2-hour OGTT between 7.8 and 11.0 mmol/L). **DIP depicts women who would be diagnosed as DIP under the WHO 2013 GDM criteria (fasting glucose of at least 7 mmol/L and 2-hour glucose of at least 11.1 mmol/L). DIP, diabetes in pregnancy; GDM, gestational diabetes mellitus; HFDP, hyperglycemia first detected in pregnancy; IFG, impaired fasting glucose; IGT, impaired glucose tolerance; OGTT, oral glucose tolerance test; T2DM, type 2 diabetes mellitus.

Fig 3. Multiple logistic regression of factors associated with T2DM.

Model statistics (observations, 200; LR Chi-squared, 167.4; p = 0.000; Pseudo R², 0.401; and log likelihood, 54.6). BMI, body mass index; HFDP, hyperglycemia first detected in pregnancy; matric edu, matric education; LR, likelihood ratio; OR, odds ratio; T2DM, type 2 diabetes mellitus.