Final answer:
The potential causes of "blue-baby" syndrome include congenital heart defects like tetralogy of Fallot and patent foramen ovale, and possibly high levels of nitrates in drinking water.
Step-by-step explanation:
"Blue-baby" syndrome, or cyanosis in infants, is a condition that can be caused by multiple factors. One potential cause is congenital heart defects, such as tetralogy of Fallot or patent foramen ovale. These conditions can result in inadequate oxygenation of the blood. Another discussed cause has been nitrates in drinking water, though studies on this link have been mixed. Infants consuming water with high levels of nitrates are at risk for this condition. It is important to note that shaken-baby syndrome is a different form of infant condition caused by physical abuse and is characterized by symptoms such as brain swelling and retinal hemorrhage.