Objectives: To describe trends and correlates of acid-suppressant therapy usage during the first year of life. Study design: A population-based cohort in a large state-mandated health fund in Israel, including members born between 2005 and 2020, was conducted. Acid-suppressant therapy initiation was defined by any purchase within the first year of life. The association between acid-suppressant therapy initiation with medical and sociodemographic characteristics was assessed via logistic regression. Results: Among 595 860 children, acid-suppressant therapy was initiated in 22 412 (37.6 per 1000). The incidence rate increased by 2.8-fold from 18.2 per 1000 in 2005 to 51.0 per 1000 in 2020, furthermore the median age at initiation decreased. Primary care providers accounted for 74.8% of prescribing physicians in 2005 vs 96.1% in 2020, whereas the prevalence of prescribing gastroenterologists decreased from 18.8% to 2.8%. Preterm birth and small weight per gestational age were associated with acid-suppressant therapy usage, with an aOR of 4.23 (95% CI 3.59-4.99), 3.05 (95% CI 2.72-3.42), and 1.65 (95% CI 1.58-1.74) for extreme, very, and moderate preterm vs term birth and aOR 1.22 (95% CI 1.16-1.28) for small weight per gestational age. Birth order was inversely associated with acid-suppressant therapy initiation, with aOR 0.62 (95% CI 0.60-0.65) for third born vs firstborns. High socioeconomic status was linearly associated with initiation, with aOR 1.12 (95% CI 1.11-1.12) per 1-point increase on a 10-point score. Conclusions: Our analysis demonstrates a substantial increase in early life exposure to acid-suppressant therapy during recent years in Israel. Correlates for initiation in early life were identified to define a population for intervention to reduce potential unnecessary use.