Objective: This study aimed to examine the association between hypo/hypercapnia and fluctuations in carbon dioxide (CO2 ) levels and severe intraventricular hemorrhage (IVH) during the initial 72 hours of life among preterm infants. Material and Methods: A retrospective study of premature infants with birth weights between 750 and 1.250 g and gestational ages of 30 weeks who required respiratory support. Blood gas measurements were collected during the first 3 days of life. Multivariate analyses were performed to assess the association between hypercapnia and carbon dioxide pressure (pCO 2 ) fluctuations and IVH. Results: Our cohort included 376 patients with a median gestational age of 28 weeks and a median birth weight of 920 g. After controlling for gestational age and birth weight, histologic chorioamnionitis and pCO 2 fluctuations remained significantly associated with severe IVH. Conclusion: Fluctuations in pCO2 over a short period may have a stronger association with severe IVH than the mere occurrence of hypo- or hypercapnia.