Early diagnosis of congenital heart diseases (CHD) is of great importance in the morbidity and mortality of the newborn. Physical examination is not always helpful in diagnosis. Screening for critical congenital heart disease with pulse oximetry is useful for early diagnosis of asymptomatic babies.

In this article, 3 cases who were diagnosed with congenital heart disease due to low oxygen saturation without respiratory problems after hospitalization in the neonatal intensive care unit for different reasons were discussed. Two patients were diagnosed with pulmonary atresia with ventricular septal defect, and one patient was diagnosed with truncus arteriosus type 4. One of the patients in whom prostaglandin E1 infusion was initiated after the diagnosis was made by echocardiography died. Surgical treatment was planned for the other two patients.

A baby without significant cyanosis who has low saturation with critical CHD screening may have ductus dependent heart disease, if respiratory distress is not observed when followed up in hospital, if a lung-induced ventilation-perfusion disorder is not considered, CHD should be considered first. In the second level neonatal intensive care units or when the opinion of a pediatric cardiology physician is not available, starting prostaglandin E1 infusion without waiting for ecocardiography and the patient is transfer to a center with a pediatric cardiology unit can be life-saving.