Is it a seizure? About 2 to 5 percent of children will have one before they're 3. More kids, though, have what looks like a seizure but isn't. "If your child isn't sick, and seems fine before and after the incident, it may not be a seizure," says Kevin Chapman, M.D., a pediatric neurologist with the Barrow Neurological Institute in Phoenix. How to tell:

What it looks like: Around feeding, your infant arches his back and extends his arms.
What it is: Gastroesophageal reflux (GER), a common digestive problem
What to do: Ask your doctor; he may suggest a new feeding schedule or formula.

What it looks like: Your infant shakes his head back and forth rapidly.
What it is: Benign infant shuddering, a reflex often triggered by happiness
What to do: Mention it to your pediatrician, just to make sure that's what it is.

What it looks like: Your infant or young child twitches a few times as he falls asleep.
What it is: Benign sleep myoclonus, a sleep disorder that usually goes away on its own by the time a child is 3 years old
What to do: Gently wake your infant to stop the movements. Mention it to your pediatrician, just to be safe.

What it looks like: Your child gets upset and holds his breath. He might turn blue, stiffen, or pass out, but he's fine in less than a minute.
What it is: A breath-holding spell, an involuntary reaction to anger, fear, or pain. These spells can begin in infancy and usually stop around age 5.
What to do: Call 911 if your child turns blue and you're not sure why. These spells are usually harmless, but tell your doc.

What it looks like: Your infant or child develops a fever, then twitches, jerks, and stiffens.
What it is: A febrile seizure. Three to 5 percent of kids will have one by age 5.
What to do: After the seizure, try to reduce the fever, and call your pediatrician right away to rule out a more serious problem.

What it looks like: Your child suddenly becomes unresponsive and might move his eyes, face, or body uncontrollably. Afterward, he's sleepy or weak.
What it is: An epileptic seizure, which occurs in only about 1 percent of children (the risk increases for developmentally delayed children)
What to do: Don't restrain him or put anything in his mouth. Call the doctor immediately, and time the seizure to tell your doc.