Objective. This retrospective study aimed to analyze the clinical evolution of newborns who presented acute vomiting without abdominal distension and who presented lactacidemia in the rooming-in area or transitional nursery in a tertiary care hospital. Material and methods. An observational, comparative, retrospective, and cross-sectional study was performed from January 1, 2021, to December 22, 2021. Records of newborns with acute vomiting were reviewed, and two groups, Group A with elevated lactate and Group B with normal lactate, were formed. Results. The sample consisted of 62 neonates, of which 41 (66%) had elevated serum lactate (Group A). Logistic regression was performed, finding that time to resolution in hours had a statistical significance of 0.003 and an odds ratio of 1.278 in Group A (18 ± 10) to restart the oral route (p < 0.05). In contrast, Group B had a higher platelet count (p < 0.001). Conclusions. We found elevated serum lactate in 66% of the neonates studied with acute vomiting without abdominal distension in the rooming-in area or transitional nursery, a finding not reported to date in the literature.