Physical & Motor Development:
Babies' physical milestones refer to body growth, particularly changes in weight and length. Motor milestones refer to their ability to move their bodies, particularly by walking.
The WHO explains that, by the age of 6 months, most babies will double their birth weight.
Here’s a rough guideline of walking milestones.
Birth to 2 months: If held in a standing position on a hard surface, your baby will move his legs as if he's walking. This walking reflex disappears around 6 weeks of age.
3 to 4 months: Does mini-pushups—lies on tummy and raises head and chest off the ground, using arms for support.
5 months: Bounces up and down when held in a standing position.
6 to 8 months: Learns to sit. Most babies also learn to crawl between 6 and 10 months, although some move straight to walking.
Cognitive development, which begins in infancy, pertains to the development of intelligence, conscious thought and problem-solving ability.
Newborn to 1 month: When awake, your baby is using his senses to get to know the world around him. He responds to the tone of your voice, your smile, and the comfort of your touch when you feed him.
2 to 3 months: Your baby’s favorite activity is watching what goes on around him. He'll delight you with his first genuine smile. By 3 months, he'll coo and gurgle, a primitive form of conversation with you.
4 to 7 months: Your baby knows his name now. When you say it, he'll even turn toward you. More attuned to your tone of voice, he either reacts joyfully or becomes distressed and cries. Able to tell apart strangers and people he knows, he may cry in the arms of someone he doesn't recognize.
Babies respond to other people from the moment they're born. Here are the steps that children typically go through.
Birth to 3 months: Makes eye contact, coos, makes faces at you. He may mimic some of your expressions.
3 to 6 months: Smiles readily and responds to her name. Interacts with new people and enjoys a game of peek-a-boo.
Language skills usually develop in an orderly fashion—a little early or a little late.
Birth to 3 months: Makes quiet cooing sounds when pleased, typically a single vowel, like ahhhh.
2 to 3 months: Cries differently in different situations. You may be able to distinguish a hunger cry from his cry when tired, for example.
3 to 4 months: Vocalizes mostly vowels; cooing becomes a little more sophisticated, with more varied sounds.
5 to 6 months: Makes his voice rise and fall, often in response to baby talk and your facial expressions.