Infants born with congenital heart disease (CHD) may require emergent treatment in the newborn period. These infants are likely to benefit the most from a prenatal diagnosis, which allows for optimal perinatal planning. Several cardiac centers have created guidelines for the management of these high-risk patients with CHD. This paper will review and compare several prenatal CHD classification systems with a particular focus on the most critical forms of CHD in the fetus and newborn. A contemporary definition of critical CHD is one which requires urgent intervention in the first 24 h of life to prevent death. Such cardiac interventions may be not only life saving for the infant but also decrease subsequent morbidity. Critical CHD cases may require delivery at specialized centers that can provide perinatal, obstetric, cardiology and cardiothoracic surgery care. Fetuses diagnosed in mid-gestation require detailed fetal diagnostics and serial monitoring during the prenatal period, in order to assess for ongoing changes and identify progression to a more severe cardiac status. Critical CHD may progress in utero and there is still much to be learned about how to best predict those who will require urgent neonatal interventions. Despite improved therapeutic capabilities, newborns with critical CHD continue to have significant morbidity and mortality due to compromise that begins in the delivery room. Fetal echocardiography is the best way to predict the need for specialized care at birth to improve outcome. Once the diagnosis is made of critical CHD, delivery at the proper time and in appropriate institution with specific care protocols should be initiated. More work needs to be done to better delineate the risk factors for progression of critical CHD and to determine which newborns will require specialized care. The most frequently described forms of critical CHD requiring immediate intervention include hypoplastic left heart syndrome with intact or severely restricted atrial septum, obstructed total anomalous pulmonary venous return and transposition of the great arteries with restrictive atrial septum.