INTRODUCTION AND OBJECTIVE: Proton pump inhibitor (PPI) use in children increases the risk of infections, prompting inquiry into the impact of prenatal PPIs exposure on serious infections in offspring. As a research gap in this area exists, this study aimed to address it by assessing the association between prenatal PPIs exposure and serious infections in infants during their first year of life. METHODS: Using the French health insurance data warehouse (SNDS) (2013-2018), we conducted a retrospective cohort study on singleton, full-term liveborn non-immunocompromised infants, stratified by PPI use during the first three months of life (early-life use). Proton pump inhibitor dispensing in ambulatory care settings during pregnancy defined exposure. Outcomes concerned any serious infections in offspring aged between 3 and 12 months. Adjusted odds ratios (aORs) were estimated using logistic regression with multivariable models to control for potential confounders. RESULTS: Of the 2,485,545 infants included, 497,060 (23.3%) were prenatally exposed to PPIs and 97,767 (4.6%) had PPI use during the first three months of life. Prenatal PPI exposure was associated with serious infections in offspring (aOR, 1.09 [95% CI, 1.07-1.10]) in infants without early-life PPIs use. No association was found for infants with early-life PPI use (aOR, 1.05 [95% CI, 1.00-1.11]). Gastrointestinal infections were the sole site with persistent significance. CONCLUSION: Prenatal PPI exposure is common and is not associated with a major risk of serious infections in infants during their first year. However, even after adjusting for several confounding factors, a weak association remains, especially in infants without early-life PPI use. While offering reassurance, adherence to clinical guidelines is still crucial.