Objective: To examine glycaemic variability (GV) and glycaemic control (GC) parameters in early pregnancy with subsequent development of gestational diabetes mellitus (GDM). Design: Longitudinal observational study. Setting: Pregnant women from KK Women and Children’s Hospital in Singapore Participants: 51 study participants in the first trimester (9-13 weeks’ gestational), and 44 participants (18-23 weeks’ gestation) in the second trimester of pregnancy. Methods: Independent t-tests were used to examine the differences in the parameters between participants who developed GDM and those who did not. Main outcome measure: GDM was determined at 24-30 weeks’ gestation using oral glucose tolerance test (OGTT). GV parameters examined were, mean amplitude of glycaemic excursion (MAGE), standard deviation of blood glucose (SDBG) and mean of daily continuous 24 h blood glucose (MBG) and coefficient of variation (CV). GC parameters measured were, J-Index and % time spent in glucose target ranges. Results: In the second trimester of pregnancy, mean amplitude of glycaemic excursions (MAGE) was significantly higher in participants who subsequently developed GDM, compared to those who did not (mean (SD): 3.18(0.68) vs 2.60(0.53), p=0.02). Other study parameters measured in the second trimester of pregnancy were not significantly different between groups. There were no significant associations between all the GV and GC parameters determined from the CGM in the first trimester with subsequent development of GDM (p>0.05). Conclusion: MAGE is an important GV parameter associated to the development of subsequent GDM in pregnant women. The findings highlight the potential value of CGM in gestational glycaemic profiling.