Infants with congenital heart disease have impaired weight gain during the first several months of life. Efforts have focused on improving weight gain and nutritional status during the first months of life. Close examination of the data suggests that the immediate postoperative period is problematic. Etiology of this early growth failure should be identified to develop effective interventions. This is a retrospective study of neonates who underwent modified systemic-to-pulmonary artery shunt, including Norwood palliation, at Children's Healthcare of Atlanta between January 2009 and July 2011. We analyzed growth from time of surgical intervention to hospital discharge. Measures of calculated weight-for-age Z-score (WAZ score) were performed using the World Health Organization's Anthro Software (version 3.2.2, January 2011; WHO, Geneva, Switzerland). Seventy-three patients were identified. Eight patients did not meet inclusion criteria. Complete data were collected on the remaining 65 patients. Median caloric intake patients received was 50.4 [interquartile range (IQR) 41.6 to 63.6] calories/kg/day while exclusively on parental nutrition. At hospital discharge, the median WAZ score was -2.0 (IQR -2.7 to -1.2) representing an overall median WAZ score decrease of -1.3 (IQR -1.7 to -0.7) from time of shunt palliation to hospital discharge. Despite studies showing poor weight gain in infants with congenital heart disease after neonatal palliation, this study reports the impact of hospital-based nutritional practices on weight gain in infants during the immediate postoperative period. Our data demonstrate that actual caloric intake during the cardiac intensive care unit stay is substantially below what is recommended.