Date Published: January 16, 2018
Publisher: Public Library of Science
Author(s): Barbara Daly, Konstantinos A. Toulis, Neil Thomas, Krishna Gokhale, James Martin, Jonathan Webber, Deepi Keerthy, Kate Jolly, Ponnusamy Saravanan, Krishnarajah Nirantharakumar, Nicholas J. Wareham
Abstract: BackgroundGestational diabetes mellitus (GDM) is associated with developing type 2 diabetes, but very few studies have examined its effect on developing cardiovascular disease.Methods and findingsWe conducted a retrospective cohort study utilizing a large primary care database in the United Kingdom. From 1 February 1990 to 15 May 2016, 9,118 women diagnosed with GDM were identified and randomly matched with 37,281 control women by age and timing of pregnancy (up to 3 months). Adjusted incidence rate ratios (IRRs) with 95% confidence intervals (CIs) were calculated for cardiovascular risk factors and cardiovascular disease. Women with GDM were more likely to develop type 2 diabetes (IRR = 21.96; 95% CI 18.31–26.34) and hypertension (IRR = 1.85; 95% CI 1.59–2.16) after adjusting for age, Townsend (deprivation) quintile, body mass index, and smoking. For ischemic heart disease (IHD), the IRR was 2.78 (95% CI 1.37–5.66), and for cerebrovascular disease 0.95 (95% CI 0.51–1.77; p-value = 0.87), after adjusting for the above covariates and lipid-lowering medication and hypertension at baseline. Follow-up screening for type 2 diabetes and cardiovascular risk factors was poor. Limitations include potential selective documentation of severe GDM for women in primary care, higher surveillance for outcomes in women diagnosed with GDM than control women, and a short median follow-up postpartum period, with a small number of outcomes for IHD and cerebrovascular disease.ConclusionsWomen diagnosed with GDM were at very high risk of developing type 2 diabetes and had a significantly increased incidence of hypertension and IHD. Identifying this group of women in general practice and targeting cardiovascular risk factors could improve long-term outcomes.
Partial Text: Gestational diabetes mellitus (GDM) is increasing, largely due to the obesity epidemic  and increasing maternal age . Although inconsistencies exist across countries for screening for GDM  and diagnostic cutoff points for the oral glucose tolerance test , reported prevalences are 2%–6% for Europe , 7% for North America , and 1%–9% and 4%–24% for white British and South Asian (SA) women, respectively, in England and Southern Ireland , reflecting the higher 10%–20% prevalence in high-risk populations . It is well accepted that the early identification and treatment of women with GDM reduces pregnancy and perinatal complications [1,6,7] and improves infant birth weights . Women with GDM are also more likely to have markers for insulin resistance and beta cell dysfunction [9–13], particularly if overweight , and GDM is a well-established predictor for progression to type 2 diabetes and carries up to a 70% lifetime risk .
The study protocol was approved by the Scientific Review Committee (SRC Reference Number: 17THIN001) of the data provider, IQVIA.
A total of 9,118 women with GDM (based on an electronic code entry for GDM) were identified in the dataset. Table 1 outlines the demographic characteristics of the women diagnosed with GDM compared with pregnant control women (matched by age and timing of pregnancy) at baseline. Mean age at the time of delivery was 33 years and ranged from 14 to 47 years. A significantly greater proportion of women with GDM compared with controls were from economically deprived areas (Townsend quintile 4 or 5), were overweight or obese (BMI ≥ 25 kg/m2, 63% compared with 35%), and had been diagnosed with hypertension (including 2.5% prior to pregnancy), but women with GDM were less likely to be current smokers (16% versus 19%). The follow-up period varied from less than 1 to 25 years (median 2.9 years). There was a high proportion of SA women (17.1%) among those with a recording for ethnicity in the GDM cohort. Fig 1 outlines the sampling frame for the total number of pregnant women, those diagnosed with GDM, and control women matched by age and time of pregnancy.
This is, to our knowledge, the first large population-based study in the UK that reports on the increased risk of cardiovascular disease in women diagnosed with GDM, and quantifies the high incidence of type 2 diabetes and hypertension for these women in the postpartum period. Women diagnosed with GDM were over 20 times more likely to develop type 2 diabetes, had almost twice the risk of developing hypertension, and were 2.8 times more likely to develop IHD in the postpartum period compared with control women. The increased risk persisted throughout the 25-year follow-up period. Despite the high risk of developing type 2 diabetes and cardiovascular disease, postpartum screening was poor, with less than 60% of women undergoing any type of screening test for diabetes in the 12 months following delivery and with the proportion declining to below 40% in the second year. Further, only half of the women with GDM had their blood pressure recorded in the second year following delivery. About a third had smoking status recorded, and very few women had lipids recorded, in the third year postpartum. The only improvement noted following publication of the 2008 NICE guidelines  was in any form of measurement for glycemia, and this improvement was only moderate.