Kong M, et al. - Physicians investigated the association between gamma-glutamyl transferase (GGT), alanine transaminase (ALT) and aspartate transaminase (AST) levels during early-middle pregnancy and subsequent risk of gestational diabetes mellitus (GDM). During early-middle pregnancy, pregnant women with higher serum GGT had a higher risk of developing GDM. A GGT level >26.9 U/L could indicate an increased risk of developing GDM later.