Hemoglobin A1c and postpartum abnormal glucose tolerance among women with gestational diabetes mellitus

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.

Women with singleton pregnancies treated 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.

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 mellitus after delivery. After adjustment for clinic, maternal age, parity, prepregnancy body mass index 25 or higher, nonwhite race or ethnicity, and gestational week at first HbA1c, we detected a trend of increased risk for impaired fasting glucose (P=.01), impaired glucose tolerance (P=.002), and any glucose abnormality (P<.001) associated with increased quartile of HbA1c at GDM diagnosis.

Hemoglobin A1c measured at GDM diagnosis may be a useful tool for identifying patients with GDM at highest risk of developing postpartum abnormal glucose.