Background:In Colombia, patients classified as obstetric low risk have maternal or fetal adverse outcomes despite the process of classification of prenatal controls, within these outcomes are pathologies associated with the alteration in placentation.Doppler of uterine arteries (DUA) is a useful method to predict complications derived from inadequate placentation, for this reason we decided to evaluate this diagnostic tool.In Bucaramanga and its metropolitan area (AMB), the prevalence alteration of DUA between week 20 and 24 of gestation in low risk obstetric patients is not known, for this reason the current study was designed.Objective: Determine the prevalence alteration of Doppler uterine artery (DUA) and its parameters (pulsatility index (PI) and resistance (RI) and Notch) in low risk obstetric patients between week 20 -24.6 of gestation in Bucaramanga and its metropolitan area.Settings: Patients were recruited in basic hospital care centers of AMB and the DUA was performed in the Hospital Universitario de Santander (HUS) Study design: Prospective cross-sectional study, in which low-risk obstetric patients with less than 24.6 weeks of gestation were recruited.The obstetric risk was corroborated and fetal biometry and DUA were performed between week 20 -24.6 to perform fetal biometry and DUA.The statistical analysis of the data was performed with the Stata program 12.1.The ethical considerations were approved by the medical ethics committee of the UIS.Results: 120 patients were recruited between 18 and 35 years old and 49.2% (59) were primigravid.The median gestational age at the time of the DUA was 21.6 weeks.There was an abnormality IP in 15.0% (18) of the patients (95% CI from 9.1% to 22.7%), of the IR in 25.0% (30) (95% CI from 17.3% to 33.7%) and presence of Notch in 10.8% (13) (95% CI from 5.9% to 17.8%).Of 18 (15.0%)patients who had impaired PI 2 had normal RI and the Notch was absent in 6.The three parameters were altered in 11 (9.2%) patients. Conclusions:The IP alteration was 15.0% (18), which was expected according the selection criteria we used to define obstetric low risk population.Taking into account the number of births / year that occur in Bucaramanga and its metropolitan area, this prevalence is not negligible and we consider that is necessary to continue this line of research to establish the relevance of performing the DUA in the low-risk population in the second trimester.