Evaluation of Early Screening for Diabetes Mellitus in Pregnancy with Hemoglobin A1c

Early diabetes screening is recommended for high-risk pregnant women risk via a 1-hour glucose challenge test (1-hour GCT). Hemoglobin A1c (HbA1c) can be obtained with initial obstetric laboratories. We sought to examine the relationship between HbA1c and 1-hour GCT for early diabetes screening in pregnancy. This is a retrospective cohort study of 204 high-risk pregnant women who underwent early HbA1c and 1-hour GCT. Simple logistic regression analysis was performed to predict abnormal 1-hour GCT and diagnosis of diabetes using HbA1c. A total of 158 (77.5%), 44 (21.5%), and 2 (1%) women had HbA1c of less than 5.7, 5.7 to 6.4, and 6.5% or higher, respectively. Seven of 158 (4.4%) women with HbA1c less than 5.7% and 8 of 44 (18.2%) with HbA1c of 5.7 to 6.4% had a diagnosis of diabetes. A positive correlation between early HbA1c and 1-hour GCT was detected. Logistic regression showed HbA1c significantly predicted the risk of diabetes but was not a good predictor of abnormal 1-hour GCT. HbA1c of 5.5% or less had a 97% or higher negative predictive value for early diabetes in pregnancy. There is a positive correlation between HbA1c and 1-hour GCT for the early screening of diabetes in pregnancy. Women with early HbA1c ≤ 5.5% could forego further testing in early pregnancy.