Gestation is a diabetogenic state due to insulin resistance. Pregnant women with higher insulin resistance are at risk of developing preeclampsia and vascular dysfunction. Fasting glucose to insulin ratio (G0/I0) and Fasting Insulin Resistance Index (FIRI = (G0&nbsp;x I0)/25) are surrogate indices of insulin sensitivity of the euglycemic-hyperinsulinemic clamp. The aim of this study was to determine G0/I0&nbsp;and FIRI in normal (n = 142) and preeclamptic pregnancies (n = 18), during the three periods of gestation, and three months postpartum. Also, 52 healthy non-pregnant women were studied. The study was approved by the Ethics Committee of the Faculty of Medicine and the participants provided written informed consent. A serum biochemical analysis of fasting insulin, blood glucose, total cholesterol, triglyceride and HDL cholesterol was done. G0/I0&nbsp;and FIRI were calculated. Statistical analyzes were performed with R software. In healthy pregnancy, G0/I0&nbsp;decreased significantly in the second (8.5 ± 4.3) and third periods (6.7 ± 3.0), compared to the first one (11.1 ± 5.7), non-pregnant women (11.3 ± 7.0) and postpartum (13.1 ± 7.9) (p<0.01). In preeclamptic patients, G0/I0&nbsp;decreased significantly from the first period (7.1 ± 1.6) to the end of pregnancy (6.2 ± 4.2) (p<0.05). In these women, G0/I0&nbsp;rose in the postpartum period (7.6 ± 4.4) without reaching the values of non-pregnant women (11.3 ± 7.0). The difference in the G0/I0, between healthy pregnant and preeclamptic women was due to the increase in basal insulin. A significant correlation was found between G0/I0&nbsp;and QUICKI, HOMA-IR and FIRI indices, during the three gestation periods and postpartum in healthy and preeclamptic, and in non-pregnant women. In healthy pregnancy, FIRI decreased significantly (p <0.05) in the first period (27.4 ± 13.7), and increased in the third period (38.4 ± 16.1 compared with non-pregnant women 33.3 ± 16.0), and decreased significantly (p <0.05) in the postpartum (27.7 ± 17.3 (p<0.01)). In preeclamptic women, the FIRI increased significantly from the second period (47.3 ± 13.7) to the end of pregnancy (45.7 ± 21.5) (p <0.05) and in postpartum (48.5 ± 28.1), compared with non-pregnant women (33.3 ± 16.0). The FIRI was not different in the third period of gestation between healthy pregnant and preeclamptic women. The FIRI was correlated with QUICKI, HOMA-IR and G0/I0&nbsp;indices during the different periods of pregnancy and postpartum, in healthy pregnant and preeclamptic women, and with the TyG and TG/HDL-c indices only in postpartum in preeclamptic women. In conclusion, these different indices of surrogate insulin resistance (G0/I0, FIRI, QUICKI, HOMA-IR, TyG and TG/HDL-c) can be used to predict insulin resistance during pregnancy. Preeclamptic women had more insulin resistance from early pregnancy and this state persists longer than in healthy pregnant women.