Objective To analyze the correlation between serum 25-hydroxyvitamin D3(25[OH]D3),insulin levels and in-sulin resistance in newborn mothers with gestational diabetes mellitus.Methods Sixty newborns of gestational diabetes pa-tients received in Puning People's Hospital from January to June 2023 were selected as the observation group,and 60 new-borns of healthy pregnant women received in Puning People's Hospital from January 2023 to June 2023 were selected as the control group.Blood samples were collected at different time points after birth,and the differences of blood glucose,serum 25(OH)D3,insulin level and insulin resistance index were compared between the two groups.The correlations of serum 25(OH)D3 and insulin levels with blood glucose and insulin resistance index of newborn babies born with gestational diabetes were analyzed.Results The blood glucose and serum 25(OH)D3 levels in the observation group at 24 and 48 h were higher than those at 12 h,and the serum insulin and insulin resistance index were lower than those at 12 h,with statistical signifi-cances(P<0.05).There were no significant differences in blood glucose,serum 25(OH)D3,serum insulin and insulin resis-tance index in control group at 12,24 and 48 h after birth(P>0.05).The blood glucose and serum 25(OH)D3 levels in the observation group at 12 h after birth were lower than those in the control group,and the serum insulin and insulin resistance index were higher than those in the control group,with statistical significances(P<0.05).The serum 25(OH)D3 was posi-tively correlated with blood glucose level(P<0.05),and negatively correlated with insulin resistance index(P<0.05).There was a negative correlation between insulin level and blood glucose level(P<0.05)and a positive correlation between insulin resistance index(P<0.05).Conclusion The serum 25(OH)D3 of newborns born of gestational diabetes mellitus is lower than that of healthy pregnant women,and the insulin level is higher than that of healthy pregnant women,and there is a correlation with blood glucose level and insulin resistance index.These two indicators can be observed to evaluate the health status of newborns born of gestational diabetes mellitus.