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    Growth and Development, Ages 1 to 12 Months - What to Expect

    Babies usually grow in natural, predictable steps, moving from one milestone to the next. During the first year you will see gains in five major areas:

    Milestones by age

    Each baby grows and gains skills at his or her own pace. It's common for a baby to be ahead in one area, such as language, but a little behind in another.

    By around 2 months, most babies:

    • Smile as a way to engage others.

    By 4 months, most babies:

    • Start using their arms with purpose. For example, babies may move their arms and squirm when excited or "swipe" at dangling objects.

    By 6 months, most babies:

    • Have doubled their birth weight.
    • Are able to sit with little or no support.

    By 9 months, most babies:

    • Get upset when you or another caregiver leaves.
    • May have begun to crawl.

    By 12 months, most babies:

    • Have tripled their birth weight.
    • Are expressive and have formed a close attachment to their parents.
    • Understand some words and begin to figure out the meaning of many others.
    • May be able to say a few words.
    • May be walking.

    Premature infants typically reach milestones later than others of the same age. But they are usually on schedule for their expected time of birth. For example, a baby born 2 months early might reach milestones 2 months later than a full-term baby born at the same time.

    Healthy babies who were born prematurely usually reach normal developmental levels for their age by the time they are about 24 months of age. Learning and thinking skills usually are first to catch up. Motor skills are often the last to catch up.

    WebMD Medical Reference from Healthwise

    Last Updated: September 09, 2014
    This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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