Section 3.2 Postnatal development

1.Growth in height and weight

At birth, babies weigh about 3.3 kg and are around 20 inches long. Boys are usually a little heavier than girls. In the first year, babies double their weight by 4 months and nearly triple it by their first birthday. They grow about 1 inch per month and increase length by 1.5 inches by age one.

2. Infants’ reflexes

Reflex behavioural patterns are manifested by a normal infant after birth. They are considered to be self-induced reflexes.

• Sucking reflex: This happens when newborns automatically suck anything placed in their mouth. It helps them get nourishment before they learn to connect the nipple with feeding.
• Rooting reflex: This takes place when an infant’s cheek is stroked, or the side of the mouth is touched. The infant turns the head towards the side that is touched with an attempt to suck.
• Moro reflex: This occurs when a neonate is startled and responds to a sudden intense noise or movement around it. When startled the neonate stretches its arms and legs, arches its back and throws his head sideways. All these behaviours disappear between 4^th - 6^th months.
• Babinski reflex: This takes place when a gentle stroke is applied on the sole of the foot whereby the neonate bends its toes and flexes the bigger toe with an effort to withdraw from the source of the stroke.
• Grasping reflex: This occurs when the neonate holds tightly onto objects placed in their palm and disappears around 4 months as they learn to grasp voluntarily.

3. Body proportions

The baby’s head grows more slowly after birth, while the body and limbs grow faster. This makes the baby less chubby and slenderer by age two.

4. Muscle and fat development

Muscles are weak and grow slowly, but fat develops quickly because milk is high in fat, helping the baby stay warm and nourished.

5. Bone development

Bones increase in number and harden over time. The soft spot on the skull (fontanel) usually closes by 1.5 to 2 years of age.

6. Teeth development

By age one, babies usually have 4 to 6 baby teeth, mainly front teeth. By age two, they have about 16 teeth, with molars appearing in early childhood.

7. Development of gross motor abilities in infancy

Gross motor skills involve the use of large muscles, like those in the arms and legs.

• In the first month, babies can lift their heads while lying on their stomach.
• By 3 months, they can lift their chest and support themselves using their arms.
• Around 3–4 months, babies can roll over.
• At 4–5 months, they can hold some weight on their legs.
• By 6 months, babies can sit without help and reach for objects easily.
• Between 7–8 months, they can crawl and stand without support.
• At 8 months, they can pull themselves up to a standing position.
• By 10–11 months, babies can walk by holding onto furniture or walls.
• By 12–13 months, most babies can walk without help.
• Between 13–18 months, toddlers can pull toys on a string
• At 10 - 11 months, infants can walk with support of furniture or by touching a wall.
• At 12 - 13 months most infants walk without assistance.
• By 13 - 18 months, toddlers pull toys attached to a string.
• By 18 - 20 months, toddlers walk or run for a short distance, walk backward without losing direction, stand and kick a ball or throw a stone or jump without falling.
• In the 2nd year, infants are capable of exploring their surrounding extensively.

8. Development of fine motor abilities in infancy: 

By age 2, infants begin to use their arms, hands, and fingers more skillfully. Coordination of hands and eyes improves significantly, helping them perform more precise actions grasping.