1 to 4 Months
When your infant is between 1 and 2 months old, he'll briefly pull his head back and turn it from side to side when you hold him against your shoulder or chest. This strengthens the muscles in his neck, shoulders, and upper back. Eventually, these muscles -- along with a maturing nervous system that can send messages from his brain to the nerves of his arms and hands -- will enable him to push up on his forearms and lift his chest off the floor.
How to Help: Even at 6 weeks old, a baby can spend a few minutes each day belly-down across your lap with his head to the side. Starting at 3 months of age, give your baby tummy time when he's awake and alert, and you're there to watch. For ten minutes several times a day, place him on a blanket on the floor, and lie down next to him.
4 to 8 Months
All that pushing up will soon pay off. Your baby's upper-body strength makes it possible for her to lean to one side and reach for toys. Her leg and abdominal muscles have developed as well, thanks to her love of kicking in the air and bringing her toes to her mouth. The result? Your baby will soon find herself rolling from her tummy onto her back. She'll master moving from back to stomach about a month later.
How to Help: Give your baby plenty of opportunities to kick her legs when she's on her back or stomach (a baby gym often encourages this motion). When your baby is playing on her stomach, sit beside her and talk -- it will encourage her to lift her head and reach for you. Or hold some toys just out of reach so she'll shift her weight and pivot to get to them. When your baby does roll over, applaud her -- she'll be eager to try it again.
5 to 8 Months
Hello, world! Your baby has a whole new view of her surroundings now that her back and abdominal muscles are strong enough to enable her to sit upright. At first, she'll need assistance from you. Soon after, she'll adopt the "tripod pose" and use her arms for support so she doesn't topple over. Only when your baby's vestibular system -- parts of the inner ear that regulate stability and balance -- has fully matured will she be able to sit with her hands resting in her lap. It will be another month before your baby is coordinated enough to move from lying on her back to sitting upright.
How to Help: Regularly hold your baby in your lap or prop her up using cushions or pillows. Research has shown that providing support around a baby's hips encourages her to sit up with confidence. In addition, rocking back and forth with your baby or holding her and letting her bounce or "dance" on your lap provides a sense of propulsion vital to the development of her vestibular system.
4 to 6 Months
Your baby's ability to reach for and hold on to an object marks a major advance for his brain and fine motor skills. Until recently, his hand could close around an object such as a finger, but the motion was pure reflex. Now, his hand-eye coordination has matured enough so that he can see a favorite toy and decide he wants it, then use the muscles in his limbs to reach out, grab it, and bring it to his mouth. Of course, his attempts will be clumsy at first -- he may use his whole hand to rake across an object when trying to pick it up. Soon, though, his coordination will be so advanced that he'll be able to transfer items from one hand to the other.
How to Help: Put soft, easy-to-grasp toys in his hands; this kind of touch stimulates the nerves in his fingers and gives him practice holding things. When your infant is on the floor, put some toys by his sides, within his reach -- it'll encourage him to turn his body to get to them. Finally, play basic games like pat-a-cake with your baby to help improve his coordination.
7 to 10 Months
Your baby is now less top-heavy, more cylindrical, and better able to coordinate his muscles -- all necessary for crawling. In addition, pushing up and using his arms to sit up has increased his upper-body strength. Still, he may not do much in the beginning besides rock back and forth on all fours. With time, however, your little one will adopt one of the 25 forms of crawling in order to make his way across the floor. (Some babies never crawl and instead move straight from sitting up to standing. This is normal and no cause for concern.) The most popular crawling styles include the "combat crawl" (forearms flat on the floor and bottom up in the air), the "crab crawl" (moving backward or sideways before forward), and the standard creep on hands and knees.
How to Help: Beginning when your baby is a month old, gently "bicycle" his legs after diaper changes to stimulate the nerves and muscles in his legs and feet. Give your baby plenty of chances to crawl on all types of safe surfaces with plenty of supervision.
8 to 12 Months
Your little one now has the strength and coordination to use furniture to pull himself into a standing position. But because his legs might not yet be sturdy enough for him to walk unassisted, he'll make do with cruising -- shifting his weight from side to side to take a short, tentative step with one foot, then bringing the other foot over to meet it, all the while holding on to furniture for support.
How to Help: Holding his hands in the air, let him walk between your legs -- this will strengthen the muscles of his legs and feet and reinforce the alternating movement needed for walking. Or stand on the other side of a long piece of furniture, such as a couch, and encourage your child to walk toward you. Steer clear of walkers, which can slow the development of the muscles in your baby's legs and are also a safety hazard. Finally, encourage cruising by placing favorite toys on low tables so your child will have to pull himself up to reach them.
8 to 12 Months
Your baby's pincer grasp -- his ability to pick up small objects using only his thumb and forefinger -- plays a major role at feeding time. To get to this point, your baby must first be able to move each finger independently, in addition to having a well-developed sense of sight and unwavering determination. At first, he'll use his thumb and two or three fingers to pick up small objects, but with trial and error he'll quickly hone this skill.
How to Help: Offer your baby small, easy-to-grasp foods such as cereal, cooked vegetables, or fruit cut into very small pieces by holding them between your thumb and index finger. He'll imitate your pincer grasp and reach for the food.
11 to 18 Months
Even at birth, your baby's body is designed for walking. If you hold your newborn in the air, her legs will move in the "stepping" pattern: a toe-heel-toe motion with alternating legs, the same pattern she will later use to walk. What she doesn't have at birth -- or for nearly a year -- is the muscle strength and balance to support her entire body and walk without help from Mom or Dad. Once your baby does start to take her first steps, watch out. She'll likely weave and lurch with her legs wide apart, her arms held out to her sides, and her feet frantically slapping with each step. But the more she walks, the sooner her awkward gait will be replaced by a fast-moving, confident stroll.
How to Help: Wheeled toys that your child can push are a great way to encourage those first steps. And playing movement games (such as the hokey-pokey) will challenge your child's balance and posture.
Your baby isn't sitting up or walking on schedule. Should you be concerned? Probably not: Your child may just be a late bloomer. Still, talk to your doctor about the following delays or warning signs.
SOURCES: Silvia Fajardo-Hiriart, M.D., medical director of the Early Steps Early Intervention Program at the University of Miami Mailman Center for Child Development; Lucy Crain, M.D., M.P.H., clinical professor of pediatrics at the University of California, San Francisco; and Karen Adolph, Ph.D., associate professor of psychology at New York University.