Abstract Objective This study aimed to investigate the mid-pregnancy blood glucose levels of women with singleton or twin pregnancies. Method The relationship between blood glucose levels and Gestational Diabetes Mellitus (GDM) was studied in women with different pre-pregnancy Body Mass Index (BMI), and the effect of GDM on twin pregnancy outcomes was analyzed. Women with twin (n= 1,985) and singleton (n= 1,985) pregnancies were categorized into underweight (BMI < 18.5 kg/m2, n= 597), normal weight (BMI: 18.5-23.9 kg/m2, n= 2,575), and overweight/obese (BMI ≥ 24 kg/m2, n= 798) groups. Results The incidence of GDM was 21.01% in women with twin pregnancies. Among the women with GDM in twin pregnancies, 38.37% had at least two abnormal blood glucose levels. The incidence of these parameters increased with preconception BMI, and the incidence of twin pregnancies was higher than that of singleton pregnancies (p < 0.001). In the normal weight and overweight/obese group, the oral glucose tolerance test glucose level and incidence of GDM were higher in women with twin than singleton pregnancies (p < 0.05). For twin pregnancies, the prevalence of selective fetal growth restriction was higher and anemia was lower in the GDM group than in the non-GDM group (all p < 0.05). Conclusion Therefore, a greater emphasis should be placed on BMI before conception, and well-controlled GDM does not increase adverse pregnancy outcomes for twin pregnancies. midpregnancy mid (GDM prepregnancy pre , (BMI) analyzed n (n 1,985 1985 1 985 185 18 5 18. kgm2 kgm kg m2 m kg/m2 597, 597 597) 18.523.9 185239 23.9 23 9 18.5-23. 2,575, 2575 2,575 2 575 2,575) overweightobese overweight obese 798 groups 2101 21 01 21.01 3837 38 37 38.37 0.001. 0001 0.001 . 0 001 0.001) 0.05. 005 0.05 05 0.05) nonGDM non all Therefore conception wellcontrolled well controlled 1,98 198 98 kg/m 59 523 18.523. 18523 239 23. 18.5-23 257 2,57 57 79 210 21.0 383 3 38.3 000 0.00 00 0.0 1,9 19 52 18.523 1852 18.5-2 25 2,5 7 21. 38. 0. 1, 18.52 18.5- 2,