AuthorCarolyn A Altman, MDSection EditorsDavid R Fulton, MDLeonard E Weisman, MDDeputy EditorMelanie S Kim, MDDisclosuresAll topics are updated as new evidence becomes available and ourpeer review processis complete.Literature review current through:Aug 2013.|This topic last updated:Aug 21, 2013.INTRODUCTIONCongenital heart disease (CHD) is the most common congenital disorder in newborns [1-3]. Critical CHD, defined as requiring surgery or catheter based intervention in the first year of life, occurs in approximately 25 percent of those with CHD [4]. Although many newborns with critical CHD are symptomatic and identified soon after birth, others are not diagnosed until after discharge from the birth hospitalization [5-7]. In infants with a critical cardiac lesion, the risk of morbidity and mortality increases when there is a delay in diagnosis and timely referral to a tertiary center with expertise in treating these patients [8].Factors that should lead clinicians to suspect CHD and screen for critical congenital heart lesions will be reviewed here. The evaluation and management of specific cardiac conditions are discussed separately [9]. (See"Cardiac causes of cyanosis in the newborn"and"Diagnosis and initial management of cyanotic heart disease in the newborn".)EPIDEMIOLOGYThe reported prevalence of congenital heart disease (CHD) at birth ranges from 6 to 13 per 1000 live births [10-15]. Variation is primarily due to the use of different methods to detect CHD, such as referral to a cardiac center or fetal echocardiographic data [14,16].The following studies provide a global perspective on the incidence of neonatal CHD: In one English health region, reported prevalence of cardiovascular malformations was 6.5 per 1000 live births [5,13]. In a population-based study from Atlanta, the prevalence of CHD was 8.1 per 1000 live births from 1998 to 2005 [12]. The most common diagnosis was muscular and perimembranous ventricular septal defect (VSD), followed by secundum atrial septal defect (ASD) (prevalence of 2.7, 1.1, and 1 per 1000 live births, respectively). Tetralogy of Fallot was the most common cyanotic CHD (0.5 per 1000 births). In a population-based study of all Danish live births from 1977 to 2005, the prevalence of CHD was 10.3 per 1000 live births [17]. Chromosomal defects were detected in 7 percent of those patients, and extracardiac anomalies in 22 percent. In a population-based study, the prevalence of CHD in Greater Paris was 9 per 1000 live births [15]. With the exclusion of VSD, 40 percent of the patients were diagnosed prenatally. The highest prevalence for CHD was observed in a population-based study from Taiwan with a prevalence of 13.1 per 1000 live births between 2000 and 2006 [9]. The most common defect was VSD, followed by secundum ASD and patent ductus arteriosus (prevalence of 4, 3.2, and 2 per 1000 live births, respectively).In preterm infants (gestational age 3g/dL.Therefore, cyanosis may not be apparent in those with mild desaturation (>80 percent saturation) or anemia (hemoglobin of 10, would require to have a saturation