At last, your baby's sleep patterns may start to settle down, giving you some rest. Many 4-month-olds sleep for a six-hour stretch through the night, though others still wake for an occasional feeding. Some babies take until age 6 months or later to sleep through the night.
Your baby's starting to draw conclusions about the world around him. He's looking at everything with curiosity, even his own reflection. Prop an unbreakable mirror next to him or sit him in front of your mirror when you're getting ready. Your baby won't realize that it's actually his image in the mirror, but that doesn't matter. He'll love to stare at his or anyone else's reflection. Your baby may stop sucking his thumb or bottle to listen to your voice. By cooing or making noises at him, and by describing even the most mundane household chore, you're not only connecting with him but also encouraging him to express himself. Wait and see if he "answers." When you're with friends, keep your baby nearby so he can hear the richness of human interaction. He'll enjoy watching the antics of other babies, toddlers, and pets, but keep up your guard: Neither he nor they know the rules of safe engagement just yet.
Anything within your baby's reach is fair game now. While he's mastering his grabbing skills, give your baby interesting things to hold: lightweight rattles that are easy to grasp, a plastic or rubber ring to hold with both hand, squeaking toys, or soft stuffed animals. Your baby will start to favor one hand for a while and then switch to the other, but you can't really tell whether he's a lefty or a righty until he's about 2 or 3 years old
Just when the days of colic and ceaseless crying seemed to be behind you; when your baby was maybe, just maybe, sleeping through the night; when she was starting to settle into a regular routine…here comes the tooth fairy to throw you both for a loop.