With the change in China’s second-child fertility policy, the numbers of older pregnant women and high-risk pregnancies have significantly increased, and the incidence of gestational diabetes mellitus (GDM) is likely to rise. GDM can cause a variety of adverse pregnancy outcomes, seriously threaten the safety of perinatal mothers and infants, and affect the long-term health of mothers and their offspring. Currently, the GDM screening period is between 24 to 28 weeks of pregnancy, but there are some shortcomings in screening at this time, since because of late diagnosis, the best time for intervention and treatment for some high-risk pregnant women may be delayed. Studies have shown that early prediction and early diagnosis of GDM is of great significance to improve pregnancy outcomes, so it is important to investigate early pregnancy prediction indexes of GDM to improve the screening efficiency for GDM and improve the management of GDM. It has been found that blood cell parameters, inflammatory factors, fat metabolism indices and liver enzyme metabolism markers have specific early predictive value for GDM. The application of these parameters combined with significant independent risk factors in the early prediction and early diagnosis of GDM will be of great value in the prevention and treatment of GDM and the prognosis of mothers and infants. This article reviews the development of routine blood test parameters during pregnancy and their value in the early diagnosis of GDM.