Congenital heart disease (CHD) remains a leading cause of infant mortality, which is even higher in infants with undiagnosed duct-dependent CHDs. Up to 39%–50% of infants with critical CHD are being discharged undiagnosed from the hospital. Infants with duct-dependent critical CHD remain well during the fetal period and may deteriorate when the ductus arteriosus (commonly called ‘duct’) closes after birth. It is critical to open or maintain ductus arteriosus patent in infants with duct-dependent CHDs. Prostaglandin E1 (alprostadil marketed as ‘Prostin VR ’) and prostaglandin E2 (dinoprostone) are used to maintain a patent ductus arteriosus and the dose of medication depends on the clinical presentation. Delay in starting prostaglandin infusion can have deleterious effects on infants and can even lead to death. These infants often present as an emergency, and professionals caring for these infants need to have a good understanding of these conditions and medications used for ductal patency.