Objective To explore the expression of hematocrit,blood flow S/D ratio and homocysteine in patients with gestational diabetes mellitus(GDM)and its effect on pregnancy outcome.Methods 86 patients with GDM in our hospital from January 2021 to January 2023 were selected as the study group,and 86 healthy pregnant women during the same period were selected as the control group.The hematocrit,blood flow S/D ratio and homocysteine expression levels were compared between the two groups of pregnant women and between the study groups of different disease severity.The incidence of adverse pregnancy outcomes was observed and recorded.Results The hematocrit of the study group was significantly lower than that of the control group,the blood flow S/D ratio and the expression level of homocysteine were significantly higher than those of the control group,the differences were statistically significant(P<0.05).There were significant differences in hematocrit,blood flow S/D ratio and homocysteine level among patients with mild,moderate and severe GDM.With the increase of the severity of the disease,the lower the hematocrit,the higher the blood flow S/D ratio and homocysteine level,and the differences were statistically significant(P<0.05).The total incidence of adverse pregnancy outcomes in the study group was significantly higher than that in the control group,and the difference was statistically significant(P<0.05).Conclusion The expression levels of hematocrit,blood flow S/D ratio and homocysteine in patients with GDM are different from those in healthy pregnant women,and they are related to the pregnancy outcome.The higher expression of blood flow S/D ratio and homocysteine and the lower of hematocrit increase the incidence of adverse pregnancy outcome in pregnant women with GDM.