Pre-analytical processing of blood samples can affect plasma glucose measurement, as on-going glycolysis by cells prior to centrifugation can lower its concentration. This has important implications for GMD diagnosis. For example, after ACT Pathology changed their glucose tolerance test (OGTT) preanalytical protocol from delayed centrifugation (after collection of the 120 min sample) to early centrifugation (within 10 min of blood collection) of blood samples collected in to sodium fluoride tubes, the GDM diagnosis rate increased from 11.6% (869 of 7509 tests) to 20.6% (1007 of 4887 tests)1. In this presentation, the pros and cons of various preanalytical processing options (e.g. type of collection tube, use of ice slurry for early cooling, and time to centrifugation) will be discussed. New data on the outcomes of pregnancies with borderline GDM, missed and not treated due to delayed sample centrifugation, compared to those with mild GDM, diagnosed and treated due to early sample centrifugation, will be presented. The need to harmonise the pre-analytical blood processing protocols for pregnancy OGTTs, whilst solving the logistical issues of performing OGTTs in different settings (e.g. rural and remote), will be discussed.