Abstract A congenital heart defect (CHD) is a structural or functional abnormality of heart that is present at birth. CHD accounts for nearly onethird of all major congenital anomalies. Screening infant with noninvasive measurement ofoxygen saturation bypulse oximetry has been proposed as an aid for early detection of duct dependent circulation. Critical congenital heart defect (CCHD) is associated with hypoxemia among infants during the newborn period, and hypoxemia represents 1731 percent of all CHDs. The CCHD screening include: hypoplastic left heart syndrome, pulmonary atresia (with intact ventricular septum), tetralogy of Fallot, total anomalous pulmonary venous return, and transposition of the great arteries with Intact Ventricular Septum. The risk of morbidity and mortality in CCHD increases when there is a delay in diagnosis and referral to a tertiary center. Babies with CCHDs usually require surgery or catheter intervention in the first year of life and represent more than one third of all CHD.
Keywords: Critical congenital heart defect; Hypoxemia; Neonates.