Sensitivity of postnatal fasting plasma glucose in identifying impaired glucose tolerance in women with gestational diabetes – 25 Years’ data

OBJECTIVE: To assess the uptake of postnatal oral glucose tolerance test and to determine the sensitivity of fasting postnatal blood sugar in predicting 2-h impaired glucose tolerance. METHODS: Retrospective study of 1961 women diagnosed with gestational diabetes mellitus. All women were offered oral glucose tolerance test six weeks post-delivery. RESULTS: Of 1961 women, 1090 (56%) returned for postpartum oral glucose tolerance test. A fasting plasma glucose of ≥6.1 mmol/l identified only 76 of 167 women with impaired glucose tolerance detected by a 2-h oral glucose tolerance test (sensitivity of 45.5%; 95%CI: 38.1–53.1). We observed a normal fasting glucose but an impaired 2-h glucose tolerance in 91 out of 968 (9.4%) women. Asian ethnicity, admission on special care baby unit and antenatal insulin therapy strongly predicted 2-h impaired postnatal blood glucose levels (P < 0.05). CONCLUSION: Although fasting plasma glucose is a convenient method, it lacks sensitivity in identifying women with impaired glucose tolerance postnatally.