Babies have cries for hunger, pain, mild discomfort — even boredom. There's even a specific cry for the bewildered state your baby is in before he falls asleep or fully wakes up. And then there's the cry that means colic. Every baby — starting as early as 3 weeks and lasting up to 3 months of age — has an upset period sometime during the day when he just needs to blow off tension. But some babies cry for three hours a day or more, three or more days a week, for three or more weeks in a row. These kids — about 15 percent of all babies — have colic.

Babies who are temperamentally sensitive and a bit intense seem most likely to be colicky — their excitement about life just seems to spill over at the end of each day. But not all children develop colic. You'll know if your child has it by the time he's 4 to 6 weeks old. Colic crying seems intense, loud, and inconsolable. Colicky babies sometimes seem to be in pain: Since crying infants swallow air, colicky babies often have distended stomachs and pass gas.

Learn more about crying and colic.