Gestational diabetes, abnormal glucose levels in pregnancy may signal future CVD risk
Gestational diabetes and abnormal glucose levels in pregnancy, as determined with an oral glucose challenge test (OGCT) at 24–28 weeks gestation, could signal a future risk of cardiovascular disease (CVD)*, according to a recent study.
“[The OGCT] provided a continuous measure of maternal glycaemia in pregnancy that related to subsequent risk of CVD in both the general obstetrical population and the subpopulation of women without gestational diabetes,” said the researchers.
Using data from the Ministry of Health and Long-Term Care of Ontario databases, researchers identified 259,164 pregnant women (without pre-pregnancy diabetes or CVD-related hospitalization) who had received a 50 g OGCT at 24–28 weeks gestation and who delivered (livebirth) between July 2007 and December 2015. Of these, 13,609 were determined to have gestational diabetes based on 1-hour post-OGCT plasma glucose concentration of ≥11.1 mmol/L (or including 7.8–11.0 mmol/L for those diagnosed with diabetes at delivery). A total of 138 CVD events occurred over the median 3.9-year follow-up period (mean age at CVD event, 35.8 years).
The researchers found that every 1 mmol/L increase in the OGCT result corresponded with a 13 percent increased risk of CVD (adjusted** hazard ratio [adjHR], 1.13, 95 percent confidence interval [CI], 1.04–1.22; p=0.004), with the risk maintained after excluding women with gestational diabetes (adjHR, 1.14, 95 percent CI, 1.01–1.28; p=0.04). [Lancet Diabetes Endocrinol 2019;7:378-384]
Further adjustment for other factors such as parity (adjHR, 1.13; p=0.003), gestational diabetes in a prior pregnancy (adjHR, 1.11; p=0.01), pre-eclampsia in the current pregnancy (adjHR, 1.12; p=0.008), hypertension (adjHR, 1.12; p=0.006), and postpartum progression to diabetes (adjHR, 1.10; p=0.03) did not affect the findings.
The OGCT results also remained associated with elevated CVD risk when the risk was limited to myocardial infarction and stroke (adjHR, 1.13; p=0.007).
Among the 245,555 women without gestational diabetes, compared with women with OGCT results of ≤7.1 mmol/L, those with abnormal levels of ≥7.8 mmol/L also demonstrated an increase in CVD risk (HR, 1.94, 95 percent CI, 1.29–2.92), as did those with results of 7.2–7.7 mmol/L (HR, 1.65, 95 percent CI, 0.99–2.76; poverall=0.003).
According to the researchers, incident diabetes may not be the only reason for the increased CVD risk, one of the reasons being that women with gestational diabetes still have an elevated CVD risk despite not progressing to diabetes. They acknowledged that the lack of data on CV risk factors, lifestyle, and BMI in this study could have affected the findings.
As for the mechanisms behind the maternal glycaemia-future CVD risk link, it has been hypothesized that being diagnosed with gestational diabetes highlights “a high-risk cardiometabolic phenotype early in its natural history”. In women with mild gestational dysglycaemia, “maternal glycaemia in pregnancy [may] provide a sensitive indicator of a latent underlying cardiometabolic phenotype and hence risk potential”, they said.
“Although [glucose screening in pregnancy] is to identify women who have gestational diabetes (in whom antenatal blood glucose management can reduce the risk of adverse obstetrical outcomes), this testing offers additional insight into health risks beyond pregnancy … The glucose screening of pregnant women that is done in obstetrical practice offers the capacity to identify future risk of CVD in women at an early point in its natural history,” said the researchers.
This can translate to early management of CVD in young women, even before the conditions manifest, they said. “Although the strategies for optimal use of this insight are still to be established, the presence of such prognostic information within data that are already being collected clinically in more than 80 percent of women offers a potential public health opportunity for ultimately reducing the global burden of CVD.”