GPT and obesity due to melanocortin 4 receptor deficiency: In this prospective cohort of pregnant women established from 2010 to 2012 in Tianjin, China, we aimed to examine 1) whether ALT levels in the first trimester predicted GDM in Chinese women; and 2) whether elevated ALT and maternal overweight/obesity in the first trimester had a synergistic effect towards increasing GDM risk.