Elevated HbA1c levels in early pregnancy linked to gestational diabetes risk
medwireNews: Women who have impaired glycemic control during the first trimester of pregnancy may be at increased risk for developing gestational diabetes, results of a US study suggest.
The researchers analyzed data from 107 women with gestational diabetes and 214 matched controls without the condition who were enrolled in the National Institute of Child Health and Human Development Fetal Growth Studies-Singleton Cohort between 2009 and 2013.
Average levels of glycated hemoglobin (HbA1c) at 8–13 weeks of gestation were significantly higher among women who later developed gestational diabetes compared with those who did not, at 5.3% (34 mmol/mol) versus 5.1% (32 mmol/mol), suggesting that women with gestational diabetes “may have impaired glucose homeostasis early in or prior to pregnancy,” say Stefanie Hinkle (National Institutes of Health, Bethesda, Maryland, USA) and colleagues.
And the team found that the risk for gestational diabetes “increased in a profound linear fashion” with increasing HbA1c levels during the first trimester of pregnancy, with each 0.1% rise in HbA1c conferring a significant 22% increased risk for gestational diabetes after adjustment for factors including obesity and family history of diabetes.
In an analysis of receiver operating characteristic curves, the sensitivity of HbA1c at 8–13 weeks for the prediction of gestational diabetes ranged from 96% for an HbA1c cutoff of 3.5% (15 mmol/mol) to 12% for a cutoff of 6.0% (42 mmol/mol), while specificity ranged from 10% to 98% at the same cutoff values.
When an HbA1c cutoff of 5.7% – the value used to define prediabetes in non-pregnant patients – was used, the sensitivity and specificity were 21% and 95%, respectively.
At this high specificity, “few low-risk women, who otherwise would not receive early screening, would be incorrectly diagnosed by an elevated first trimester HbA1c level,” write the researchers in Scientific Reports.
“This presents a unique opportunity for earlier interventions in these women which would be ideal as [gestational diabetes] is associated with adverse pregnancy outcomes such as macrosomia,” they add.
Hinkle and team also observed that the addition of HbA1c improved the accuracy of a prediction model based on conventional risk factors including age, pre-pregnancy BMI, and history of gestational diabetes. The model including HbA1c correctly distinguished between women with and without gestational diabetes on 65% of occasions, compared with 59% of occasions for the model using conventional risk factors alone.
These findings “require replication,” but suggest that HbA1c “could be used to improve early risk-stratification and screening [for gestational diabetes] in women with elevated levels,” say the study authors.
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