Abstract Background Congenital heart diseases (CHD) are one of the most prevalent malformations, and the screening tests to identify critical congenital heart disease (CCHD) is the pulse oximetry test, with subsequent investigation and treatment. Objective To quantify positive pulse oximetry tests and verify the prevalence of CCHD detected by it in asymptomatic newborns, ≥35 gestational weeks, in a Brazilian maternity hospital. Methodology This is an observational, retrospective, quantitative, analytical and cross-sectional study, conducted from October 2020 to May 2022, in a maternity hospital in southern Brazil, through the collection of records of positive oximetry pulse tests, following the norms of screening CCHD test of the Brazilian Society of Pediatrics (SBP), after they were evaluated with echocardiography for confirmation or exclusion of CHD. Results A total of 5,667 newborns were evaluated in this study, according to the inclusion criteria; 0.17% (n = 10) had a positive pulse oximetry test. Regarding the results of the echocardiography of the neonates with a positive test, two were normal, seven were cases of patent foramen ovale (PFO), and one was a case (0,017%) with interatrial communication (IAC) diagnosis. In the same period, five neonates with CCHD were born, symptomatic, diagnosed by physical examination, and referred to neonatal intensive care units (NICU) before taking the neonatal cardiac screening (< 24 hours of life). Conclusion The prevalence of positive pulse oximetry tests was 0.17% and none CCHD was detected. Five cases of CCHD were born in this period, but they were diagnosed before the recommend time to perform the screening test. CHD (CHD malformations (CCHD treatment 35 ≥3 weeks observational retrospective quantitative crosssectional cross sectional study 202 2022 Brazil SBP, SBP , (SBP) 5667 5 667 5,66 criteria 017 0 17 0.17 n 10 normal PFO, PFO (PFO) 0,017% 0017 (0,017% IAC (IAC diagnosis period symptomatic examination NICU (NICU < ( 2 life. life . life) 3 ≥ 20 (SBP 566 66 5,6 01 1 0.1 (PFO 0,017 001 (0,017 56 6 5, 0. 0,01 00 (0,01 0,0 (0,0 0, (0, (0