['Congenital heart disease is the leading cause of death in the first year after birth. Prenatal diagnosis of the disease can optimize the preoperative condition of the patient and may help in the prevention of acidosis. In this retrospective study we compared the occurrence of metabolic acidosis in patients with and without prenatal diagnosis of a congenital heart disease.', 'Data of 408 patients who needed an operation for congenital heart disease within 31 days of life were analyzed retrospectively. Arterial blood gases at fixed time intervals and worst blood gas of 81 patients with and 327 patients without a prenatal diagnosis were compared, categorizing the patients on ductus dependency, anticipated univentricular or biventricular repair, and left-sided, right-sided, or no heart obstruction.', 'In the overall group significant differences in lowest pH, lowest base excess, and highest lactate level were found, with metabolic acidosis more common among the patients with a postnatal diagnosis. In the group of patients with ductus-dependent congenital heart disease, the difference between patients receiving a prenatal and those receiving a postnatal diagnosis was more significant than in the group with non-ductus-dependent lesions. Analyzing patients with right-sided, left-sided, and no obstruction separately, significant differences were found in the group with left-sided heart obstruction for lowest pH and base excess and in the group with right-sided heart obstruction for lowest base excess.'] Does prenatal diagnosis of congenital heart disease affect preoperative acidosis in the newborn patient?