Your 4-month-old is growing more and more alert by the day. Babies at this age love to express themselves through smiles, laughs, gurgles, and coos.
Fourth-Month Baby Milestones: Growth | By month four, your baby’s weight will likely have doubled from birth. If you’re concerned that your child isn’t eating well or isn’t gaining enough weight, talk to your pediatrician.
Fourth-Month Baby Milestones: Motor Skills | Your baby is becoming more dexterous and doing more with her hands. Her hands now work together to move a toy or shake a rattle. In fact, those hands will grab for just about anything within reach, including a stuffed animal, your hair, and any colorful or shiny object hanging nearby. You might want to remove any earrings or necklaces if you don’t want to experience a painful tug.
Anything your baby is able to pick up will likely end up in her mouth — tasting is one of the ways she explores her world. It’s crucial that you don’t leave small items lying around that your baby could choke on. Anything that can fit inside a toilet paper tube is too small to be within finger’s reach of your 4-month-old. By now, your baby’s head should no longer be wobbly. Four-month-olds have pretty good head control while sitting supported, and they can hold their head and chest upright while lying on their stomach during tummy time. They also can kick and push with their feet. Some babies have even figured out how to roll from tummy to back at this point.
Fourth-Month Baby Milestones: Sleep | By your baby’s fourth month, you both should be enjoying a full night’s sleep. At this age babies typically can sleep seven to eight hours in a row. Add in two naps, and your baby should be sleeping a total of 14 to 16 hours a day.
Fourth-Month Baby Milestones: The Senses| During the first three months, babies have a lot of trouble distinguishing color contrasts, which was why your newborn preferred bright colors and black-and-white objects. Now at four months, your baby’s vision has sharpened to about 20/40. Babies at this age can pick out more subtle color contrasts, such as a red button on a red shirt. They also can see across the room, although they still prefer looking at people close-up.
Your baby’s eyes should move together smoothly and follow objects and people around the room. If you notice crossed eyes or any other vision problems, be sure to mention them to your pediatrician. You also may notice that your baby’s eyes are starting to change color. Lighter-colored eyes may go through several changes before settling on their final shade at about six months.
Resource from : http://www.webmd.com