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Baby’s First Year: How Infants Develop

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WebMD Feature
Reviewed by Renee A. Alli, MD

From helpless newborn to active toddler: It takes just 12 short months for your baby to undergo this incredible transformation. Babies grow and change at an astounding pace, and every month brings new and exciting developments.

New moms and dads often wonder what to expect next and how to know if their baby’s development is on target. Instead of focusing too much on developmental milestones, however, it’s important to remember that babies all develop at their own pace. There’s a fairly wide “window” for when it is normal for a baby to reach a particular developmental stage.

“If your baby reaches one milestone sooner, she may reach another one later, because she’s so busy perfecting the other skill,” says Jennifer Shu, MD, pediatrician and co-author of Heading Home with Your Newborn.

Some babies may say their first word at eight months, while others don’t talk until a little after the one-year mark. And walking may start anytime between nine and 18 months.

Keeping those kinds of variations in mind, here’s what your baby may be doing during each three-month stage of the first year.

Baby Development: One to Three Months

During this first development stage, babies’ bodies and brains are learning to live in the outside world. Between birth and three months, your baby may start to:

  • Smile. Early on, it will be just to herself. But within three months, she’ll be smiling in response to your smiles and trying to get you to smile back at her.
  • Raise her head and chest when on her tummy.
  • Track objects with her eyes and gradually decrease eye crossing.
  • Open and shut her hands and bring hands to her mouth.
  • Grip objects in her hands.
  • Take swipes at or reach for dangling objects, though she usually won’t be able to get them yet.

Baby Development: Four to Six Months

During these months, babies are really learning to reach out and manipulate the world around them. They’re mastering the use of those amazing tools, their hands. And they’re discovering their voices. From 4 to 6 months old, your baby will probably:

  • Roll over from front to back or back to front. Front-to-back usually comes first.
  • Babble, making sounds that can sound like real language.
  • Laugh.
  • Reach out for and grab objects (watch out for your hair), and manipulate toys and other objects with her hands.
  • Sit up with support and have great head control.

 

Baby Development: Seven to Nine Months

During the second half of this year, your little one becomes a baby on the go. After learning that he can get somewhere by rolling over, he’ll spend the next few months figuring out how to move forward or backward. If you haven’t baby-proofed yet, better get on it!

  • During this time period, your baby may:
  • Start to crawl. This can include scooting (propelling around on his bottom) or “army crawling” (dragging himself on his tummy by arms and legs), as well as standard crawling on hands and knees. Some babies never crawl, moving directly to from scooting to walking.
  • Sit without support.
  • Respond to familiar words like his name. He may also respond to “No” by briefly stopping and looking at you, and may start babbling "Mama" and "Dada."
  • Clap and play games such as patty-cake and peekaboo.
  • Learn to pull up to a standing position.
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