© 2021 Japan Society of Obstetrics and Gynecology.Objective: In this study, we aimed to compare vascular function at trimesters 1, 2, and 3 between obese and normal pregnant women through brachial artery flow-mediated dilatation (FMD), uterine artery Doppler, and umbilical artery Doppler measurements. Methods: Pregnant women between the ages of 18 and 40 who presented to our clinic were included. Brachial artery FMD, uterine and umbilical artery Doppler, and clinical parameters of 40 obese pregnant women from each trimester between 11 and 14 weeks, 24 and 28 weeks, 37 and 40 weeks and control pregnant group in the same number and gestational week were examined. Results: In all three trimesters, the FMD value was lower in obese pregnant women compared to normal women with adequate weight (p < 0.001). In obese pregnant women, lower FMD values were observed in the second trimester compared to other trimesters (p = 0.011) Cut-off value of FMD below 14.35 in obese pregnant women was found to be associated with gestational diabetes mellitus. Uterine artery Doppler in obese pregnant women started to increase from the second trimester compared to normal women with adequate weight. Conclusion: Obese pregnant women have endovascular dysfunction compared to normal pregnant women and this becomes evident from the second trimester.