At four months old, babies usually range from 23 inches long and 11 pounds (10th percentile) to 25.5 inches long and 15.75 pounds (90th percentile).

Arta may be able to play alone with his toys for up to 15 minutes. The ability to entertain himself for longer and longer periods is a big milestone - and one for which you'll no doubt rejoice! You'll also begin hearing him happily cooing away with different toys in an attempt to copy the voice inflection and rhythm that he hears from you and others. Sometimes Arta may hold a sound while running it through an array of different pitches and volumes. In my house we called this "singing." My mother called it "screeching," but it's easier to appreciate if you call it "singing." It also makes it easier to call it that in the grocery store line when he belts one out loudly. If you say something like, "Are you going to sing for everyone in the supermarket?" people will generally laugh and forgive the ear-splitting outburst.

Your little one has come a long way in four short months. He is able to hold his head steady when he's in an upright position; and while he is probably not able to sit unassisted, he will love the view offered by being perched in a highchair if he's firmly supported by pillows, rolled towels or blankets. Your lap will be another wonderful place to sit and view the world.

Arta has probably discovered a new favorite toy: his feet! Your little contortionist will easily stick his feet in his mouth when on his back and will play with his toes. Games like "This Little Piggy Went to Market" will amuse you both.