Hemoglobin A1c and Postpartum Abnormal Glucose Tolerance Among Women With Gestational Diabetes Mellitus

Abstract

Objective To analyze the association of hemoglobin A1c (HbA1c) at gestational diabetes mellitus (GDM) diagnosis with postpartum abnormal glucose in a cohort of women with GDM. Methods Women with singleton pregnancies managed for GDM at a large diabetes and pregnancy program located in Charlotte, North Carolina who completed a postpartum 2-hour oral glucose tolerance test were eligible for inclusion in this retrospective cohort study. Clinical information, including maternal HbA1c at diagnosis was abstracted from medical records. A parametric survival model was used to assess the association of HbA1c at GDM diagnosis with postpartum maternal abnormal glucose including impaired fasting glucose, impaired glucose tolerance, and any postpartum abnormal glucose. Results Of the 277 postpartum women with GDM 75 (32%) had impaired fasting glucose, 61 (28%) had impaired glucose tolerance, and 15 (9%) were diagnosed with type 2 diabetes after delivery. After adjustment for clinic, maternal age, parity, prepregnancy BMI 25 kg/m2 or higher, non-white race or ethnicity, and gestational week at first HbA1c we detected a trend of increased risk for impaired fasting glucose (p=0.01), impaired glucose tolerance (p=0.002), and any glucose abnormality (p <0.001) associated with increased quartile of HbA1c at GDM diagnosis. Conclusion HbA1c measured at GDM diagnosis may be a useful tool for identifying GDM patients at highest risk of developing postpartum abnormal glucose.

One‐hour oral glucose tolerance test plasma glucose at gestational diabetes diagnosis is a common predictor of the need for insulin therapy in pregnancy and postpartum impaired glucose tolerance

“…Similarly, other studies have shown that plasma glucose levels in a 75‐g OGTT at 1 h were associated with IGT. In contrast, HbA1c, 2‐h glucose levels in a 75‐g OGTT, fasting plasma glucose, 2‐h plasma glucose, antepartum insulinogenic index, insulin treatment, family history of diabetes and ethnicity were also reported to be predictors for IGT. Some studies did not evaluate the association between antepartum plasma glucose levels in a 75‐g OGTT at 1 h and postpartum IGT.…”

Measuring glycated haemoglobin in women with gestational diabetes mellitus: How useful is it?

“…In women with GDM, measuring HbA1c during pregnancy may help determine the risk for developing type 2 diabetes, impaired fasting glycaemia or impaired glucose tolerance post‐partum . However, the use of HbA1c for diagnosing GDM has been disappointing, as there is substantial overlap between women with normoglycaemia and women with GDM .…”

SUGAR: Spotting Undiagnosed Glucose Abnormal Results—A New Protocol To Increase Postpartum Testing Among Women With Gestational Diabetes Mellitus

“…The possibility that the insulin resistance of a recent pregnancy could cause overdiagnosis via a "false positive" HbA 1c is unlikely based on three studies demonstrating an isolated postpartum HbA 1c has a lower sensitivity for dysglycemia than an OGTT or FPG/ HbA 1c combination. 37,39,65 If an office testing protocol can promote high testing rates then such a protocol will overcome any limitations in sensitivity (►Table 2). The ability to generalize these results to clinics where the majority speak English as their primary language could be argued, but while the prevalence of Spanish speakers was not different between the two treatment groups and communication directly or via an interpretation service has the ability to convey the same information, the study was not designed with this subgroup analysis as an end point.…”

“…36,37 Women diagnosed with GDM were referred for dietary counseling and home glucose monitoring. Insulin or glyburide therapy was initiated for women whose fasting sugar were consistently > 95 mg/dL (5.3 mmol/L) or 2-hour postprandial values were > 120 mg/dL (6.7 mmol/L).…”

“…34,35 Studies in a general medical population and those with GDM found that an HbA 1c /FPG combination was 75 to 95% sensitive at detecting those who had any abnormality on an OGTT. [36][37][38][39] However, these studies did not assess the ability of a testing regimen to improve the rates of postpartum glucose tolerance testing. In our Obstetric Clinic, the historical rate of postpartum testing was 45%.…”