en 39830326 <p>Background: The purpose of the current study was to compare the color Dop-pler findings of uterine arteries and perinatal outcomes in pregnant women with and without previous cesarean section (C/S).<br /> Methods: This cohort study enrolled 308 pregnant women aged 20-35 without underlying diseases, with at least one previous pregnancy and childbirth. The participants were divided into two groups: 154 women without C/S and 154 women with C/S. Baseline data were collected, followed by uterine artery Dop-pler scans. Then, the perinatal outcomes, including pre-eclampsia, intrauterine growth restriction (IUGR), premature delivery, and birth weight were evaluated.<br /> Results: The average age of patients in the C/S group was 30.46&plusmn;3.81, which was significantly higher than the non-C/S group (28.86&plusmn;4.64). It was found that uterine artery resistance was higher in women with C/S history (1.11&plusmn;0.44, p&lt;0.001) compared to those without (1.00&plusmn;0.37, p&lt;0.001). Pre-eclampsia inci-dence was also higher in C/S group (16.1%, p=0.042) compared to non-C/S group (9.1%, p=0.042). The incidence of preterm birth in the C/S group (p=0.209), the incidence of IUGR (p=0.791), and the average birth weight (p=0.291) in the two groups did not differ significantly.&nbsp; The average gestational age in the C/S group was 37.54&plusmn;1.4, and in the non-C/S group was 38.01&plusmn;1.99 weeks. The results were not affected by potential confounders such as age, the time interval between pregnancies, and also body mass index.<br /> Conclusion: Previous cesarean section can significantly increase the uterine ar-tery resistance in subsequent pregnancy.</p> Cesarean section, Color doppler ultrasonography, Pre-eclampsia, Uterine artery resistance, Uterine artery 211 219 https://www.jri.ir/article/140240 https://www.jri.ir/documents/fullpaper/en/140240.pdf NedaHashemiEndometriosis Research Center, Iran University of Medical Sciences, Tehran, Iran112167ArashMohazzabSchool of Public Health, Iran University of Medical Sciences, Tehran, Iran122717MaryamMoshfeghiDepartment of Endocrinology and Female Infertility, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran122749SamanehRokhgirehEndometriosis Research Center, Iran University of Medical Sciences, Tehran, Iran112170RoyaDerakhshanEndometriosis Research Center, Iran University of Medical Sciences, Tehran, Iran112168NasrinSanaei NasabShahid Akbarabadi Clinical Research Development Unit (ShACRDU), School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Irannasrin_sanaei@yahoo.com122750