Physical Development

It's been a busy year for your little one--he's grown approximately 50 percent taller and tripled his weight. The average height for a 12-month-old is 28 to 32 inches, and his weight may range from 18 to 24 pounds. (If he kept growing at this rate, he'd weigh almost a ton by the time he turned 5! Luckily, weight gain tapers off around now.) Most pediatricians don't give vaccinations at one year, so your doctor probably won't schedule an appointment until your child is 15 months old. However, you may want to request an appointment if you have questions or concerns.

Social Development

Up until now, chances are you were able to distract your baby from things that were off-limits--the VCR, for instance, or his older brother's Lego set--by offering alternatives. But one day soon, he may respond to an attempt to redirect him by turning bright red, falling to the floor, pounding his fists and feet as hard as he can, and screaming loud enough to rattle the windows.

Welcome to the world of the toddler tantrum. Although tantrums are disturbing, try to distance yourself by viewing them as a dramatic performance--your child is using every tool at his disposal to make his displeasure known. Unless you want the performance to repeat itself several times a day, however, don't give in to his demands. Don't spank him or yell at him--just stand there and let him scream himself out without responding. (If you're in a public place, this may be embarrassing, but it really is essential.) After a few minutes, he will calm down. Most important, he will get the message that this particular tool does not do the job, and he'll eventually drop it from his repertoire.

Intellectual Development

Although he may be selective in his responses, your baby understands "no" and many other instructions by this time. After a year of intense study, he can read your expressions, gestures, and tone of voice with great accuracy even if he doesn't yet understand your words. Some babies turn the process into a game--they'll approach a forbidden area, then back off, shaking their heads and repeating "no, no, no" all the while. Praise your child to the skies if you see him exhibiting these early signs of self-control, but don't be surprised if he reverts to his earlier behavior tomorrow.

Note: The information above offers general guidelines, but all babies develop differently, and few hit their milestones precisely when the conventional wisdom says they should. If your child was born prematurely, you may want to use your due date as a baseline for following baby's development.