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Development of a 9-Month-Old

By Juniper Russo ; Updated June 13, 2017

During a baby's ninth month of life, she experiences fairly rapid growth and development. Children's Hospital Boston notes that a 9-month-old will gain an average of 1 lb. in a month and may achieve the developmental milestones that indicate a state of physical, cognitive and social well-being. Each child will experience his own pattern of growth and developmental function; however, most 9-month-olds fall within the broad spectrum of normal development.

Areas of Development

The American Academy of Pediatrics recognize five basic categories of early childhood development, and a baby experiences rapid development in all these areas during the ninth month of life. Social skills involve a child's ability to interact with adults and other children. Linguistic skills apply to his ability to verbally communicate. Cognitive development is how a child learns to understand concepts. Gross motor skills involve a child's use of his large muscle groups, including his torso and legs and fine motor skills involve the use of the hands and other small muscles.

Physical Milestones

Children's Hospital Boston states that at the end of the ninth month, a baby generally displays the pincer grasp, a fine motor skill that enables her to pick up a small object using her thumb and forefinger. A 9-month-old may sometimes develop key gross motor skills, including the ability to crawl, pull up on furniture, bang a toy against a table and sit unsupported. Parents of bottle-fed babies may begin the process of weaning from the bottle to a cup; children may require several months to master this fine motor skill.

Cognitive Development

The ninth month of life is a critical phase in a baby's linguistic, social and cognitive development. By nine months of age, most babies can babble with two-syllable sounds (such as "ma-ma" or "da-da") and some will intentionally speak intelligible "words" or names. A 9-month-old baby is busy rapidly expanding her understood vocabulary; she may learn to associate words with actions, objects and people. At this age, many children have strong bonds with their parents and demonstrate fear of strangers. Additionally, most babies develop the concept of object permanence—the ability to understand that objects exist even when they are hidden—by the end of the ninth month.

Cognitive and Social Development

The U.S. National Institutes of Health recommend that children attend well-child visits—also called preventative care visits or screening visits—at certain key stages of early childhood development, including the ninth month of life. At a baby's nine-month well-child visit, a pediatrician will ask parents questions regarding her physical development. Abnormal development may rarely indicate the presence of a serious condition; if a baby has not reached certain critical milestones, the doctor may refer parents to an expert for further evaluation or treatment.


No one can change the way a baby is wired—most children will reach developmental milestones at roughly the same time regardless of which parenting styles are used. However, parents and caregivers can encourage a 9-month-old baby's development using exercises and interactive play. Parents should use a wide variety of words and sounds when talking to a baby. Games like pat-a-cake, peek-a-boo and "so big" can help a child learn concepts and interactions. Nine-month-old babies also tend to enjoy daily reading; picture books can help to expand a baby's understood vocabulary. If a baby seems to be developing slowly or abnormally, parents should address these concerns with a qualified practitioner.

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