Physical Development

Conventional wisdom has it that most babies sleep through the night--loosely defined as six to eight hours--by 12 weeks of age. If this is true for your child, congratulations! Ironically, you may find that your baby has trained you to get up every three hours, whether he cries or not. Two a.m. may find you waking in a panic, rushing into his room, and rousing him out of a sound sleep to make sure he's all right!

If your little one isn't an "all-nighter" at this age, don't lose hope: Many babies continue to wake every few hours for another month or so, then suddenly amaze their parents by sleeping 10 hours or more without a break. To help reduce the number of night wakings, increase the size of his bedtime feeding. Don't change his diaper during the night unless it's absolutely necessary, and try not to rush to his room the minute you hear his voice. Everyone wakes several times during the night, and your baby needs to learn how to fall back asleep on his own. You may find that, left to his own devices, he nods off again after a minute or two.

Social Development

Just as your baby is starting to sleep more consistently, he's also crying a lot less when he's awake. There are several reasons for this miraculous change:

• You've learned to anticipate and meet many of his needs, making crying less necessary.
• His nervous system is maturing, and with it, the ability to cope with stress.
• He is finding new ways to communicate: squeals of frustration, joyous giggles, whimpering when he's tired.
• If he's had colic, symptoms generally start to ease around this time.

Experts agree that the more promptly and consistently you respond to your child during the first six months of his life, the less demanding he is likely to be when he is older. Once he is completely secure in your affections, he'll be able to separate from you over time and become a happy, independent person.

Intellectual Development

It's been said that, for babies and toddlers, "repetition is the soul of wit". In addition to amusement, the repetition of simple activities has another important function: It helps build memory. The more an act is performed, the more likely it is to be remembered and a memory trace established in the brain. Once a baby can remember things from one day to the next, he'll be able to add new behaviors to his existing repertoire rather than "reinventing the wheel".

A study by the Educational Testing Service suggests that 3-month-olds have developed short-term memory--they're able to recall repeated signals well enough to become bored by them. At the same time, it's clear that your baby remembers you well enough to brighten when you enter the room. From this point on, he'll be constantly enhancing his memory skills.

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.