Comparison of oral and intravenous glucose tolerance tests in the diagnosis of diabetes in pregnancy.

Forty potentially diabetic patients in the third trimester of pregnancy had an oral glucose tolerance test (OGTT)) and an intravenous glucose tolerance test (IVGTT); in only three were both test "diabetic". Of the 21 patients with a normal OGTT, 9 were "borderline" and 3 "diabetic" when tested by an IVGTT. Patients with an abnormal IVGTT but a normal OGTT were left untreated and allowed to go into labour spontaneously with a favourable outcome. There were no convincing relations between the results of the GTTs and levels of insulin, HPL or cortisol.