The days after a baby is born are some of the most special for a parent, but they can also be frightening. That was the case for late night host Jimmy Kimmel recently after he said a nurse noticed that his newborn son was slightly purple in color.

Physicians at Cedars-Sinai hospital determined that he had a congenital heart defect (CHD) called Tetralogy of Fallot that required surgery. While nurses were able to identify the condition early, in some cases, it can take a few days to become symptomatic.

Experts say one sign to keep an eye out for is a rapid breathing pattern. “Some newborns may be breathing so fast, and working so hard to breathe, that they do not eat,” says Frank Counselman, MD, EVMS Foundation Distinguished Professor in Emergency Medicine Professor and Professor and Chair of Emergency Medicine. “A blue tint to the skin, like the nurse noticed, is also a prominent sign because it suggests that there’s a lack of oxygen in the blood.”

Fortunately, many CHDs are treatable. In this case, Mr. Kimmel’s son was transferred to Children’s Hospital Los Angeles where he had open-heart surgery. He says the procedure went well, but his son is expected to undergo future surgeries.