Every baby develops at his own rate. In "Caring for Your Baby and Young Child," the American Academy of Pediatrics notes that although it's normal to be proud when your child walks at 12 months, there probably isn't a significant developmental difference between him and a child who walks at 16 months. The time to worry, they say, is when a child fails to reach these milestones at all or reaches them and regresses.
Types
The government's Medline Plus website describes five categories of development. The first, gross motor skills, allows your baby to move, turn, sit, crawl and walk. Fine motor skills involve coordinated movements such as picking up a piece of food or holding a crayon. Sensory development occurs as your baby learns to smell, touch and use her senses to explore her environment. Language development starts as soon as your baby makes sounds and continues as she learns individual words and their meanings. Social development refers to your baby's ability to interact with others.
Verbal Development Timeline
Although every child is different, some developmental milestones fall into predictable timelines. According to the Centers for Disease Control and Prevention's Milestones Chart, by 7 months your baby should know his name, babble and express basic emotions with his voice. Expect single-word expressions by 12 months, with short sentences and full recognition of family members and many household objects by two years.
Physical Development Timeline
Gross motor skills begin to appear by three months of age, according to the CDC. Your infant should be able to stretch, kick and raise her head when lying on her belly. She'll start to sit at around 7 months, start to crawl by 12 months and walk steadily on her own by 24 months.
Cognitive Development Timeline
According to the CDC, by 7 months of age, your baby should be reaching for things and, if he gets them, investigating them with his hands and mouth. By one year, your baby will likely be able to use a cup, pick up the phone and identify familiar people and objects. Shapes and colors become distinct by age 2, while 3-year-olds can do simple puzzles and use their imaginations to invent games. Four-year-olds can learn to count, remember stories they've been told and perform tasks that require multiple steps to complete.
Negative Factors
Your baby's growth and development---both physical and mental---can be harmed by food and beverages you consume during pregnancy. According to the American Academy of Pediatrics, a mother's alcohol consumption during pregnancy can cause physical symptoms ranging from heart defects, club foot and a curved spine to mental effects such as retardation. Any non-physician-approved medications or vitamin supplements can also cause developmental problems for your baby. The AAP notes that high doses of vitamin A can trigger physical abnormalities. Similarly, the high mercury levels in certain fish can damage a fetus's developing brain and nervous system.
