Baby's first year of physical development


Brain development

Your newborn’s brain is only about a quarter developed, which makes sense when you compare the size of her head to that of an adult.

The fontanelles

She has 2 soft spots, known as fontanelles, on her head. These are areas where the bones of her skull have not yet fused together, which allows for rapid brain growth in her first few months. Her fontanelles will close after about 18 months.

By age 1

By the time she is 1, your baby’s brain has reached two thirds of its adult weight. Her senses and skills have developed at an amazing rate and she should be able to say 1 or 2 words. The rapid growth of her brain indicates how much she has learnt in this short period.

Head and hair

Shape of the head

Your newborn baby’s head might look a bit distorted and elongated. This is due to the immense pressure that was exerted on it during birth, and after a few weeks it should return to a normal shape.

Size of the head

Her head may also look a bit out of proportion when compared to her body size. The circumference of her head is an indicator of her growth and development.

Your baby's hair

The hair your baby was born with will probably fall out within a few weeks, and the hair that grows back will look very different.

By age 1

By the time she is 1, your baby’s fine hair has thickened and grown in length. She might even have a few wispy curls framing her face.


Baby's eye colour

Most newborns are born with dark blue or greyish eyes. Your baby’s true eye colour won’t develop until she is 6 months old.


She can’t see much at birth, but she can distinguish light, shadows, shapes, contours and movement. Her vision will develop as her brain matures and the muscles around her eyes get stronger.

By age 1

By the age of 1, your baby’s vision is nearly fully developed. It might still be a bit difficult for her to judge speed and distance, but she should be able to follow fast-moving objects.


Rapid weight gain during the first 6 months

A newborn’s weight ranges from 2.3kg to 4.9kg, and during the first 6 weeks your baby’s weight will increase by approximately 0.9kg to 1.6kg.

Weight gain begins to slow by age 1

Your baby probably gained a lot of weight during her first 6 months, with her weight gain slowing down after this period. By the end of her first year it would have reduced even more and she should only be gaining about 280g a month by now.


Growth spurts

Most babies measure between 35cm to 57cm. By 6 weeks of age your baby will probably measure between 51cm to 62cm. She will also go through several growth spurts during her first 6 months, and her body size will soon become proportionate to her head, which may initially seem a bit big.

Growth begins to slow down during her second year

Your baby’s growth will slow down in her second year of life. This is because babies grow faster in their first year than they ever will again. The average baby grows by about 25 to 30cm in the first year.


The diaphragm is the hardest working muscle in your baby's body

Most of your baby’s muscle power goes towards her breathing – her diaphragm is the hardest working muscle in her body. As she grows, her muscles will develop from the inside out, and from top to bottom.

Her head will fall back if it’s not supported, but by the time she’s 6 weeks old, she could be able to lift it slightly.

By age 1

By the time she is 1, your baby has enough control over the muscles in her legs and feet to support herself while standing.


Increasing self-awareness and development

By kicking her legs up into the air, your baby is discovering the space around her. These movements are all reflexes that help her to increase her self-awareness and development.

As she learns to identify her body and the space around it, as well as how to control her limbs, she will love toys that encourage movement, like a baby gym.

By age 1

With increased muscle control comes increased mobility. At 1 year your baby should be standing on her own and may even cruise along while holding onto some furniture or you.


Newborns have little control over their limbs, and are incapable of intentional movement. This means that pretty much every movement they make is a reflex.

The grasp reflex

Your baby’s grasp reflex allows her to grab onto your fingers tightly.

The rooting reflex

Her rooting reflex is responsible for helping her feed by turning her head towards you and opening her mouth.

The Moro reflex

She also has a Moro reflex, which causes her to stiffen and extend her arms and legs, bringing them close to her chest, when she is startled.

Developing fine motor skills

As she grows older she will learn how to control these reflexes and develop fine motor skills with which to grasp and hold onto objects.

By age 1

By a year old your baby will be able to hold onto a crayon and maybe even scribble a bit on a piece of paper, or your walls! She’ll have developed strong enough motor skills to hold onto objects and enough coordination to use a utensil at mealtimes.

Baby fat

Muscle tone

From the time she is a newborn, your baby will be gaining weight faster than she’ll be growing in length. This contributes to her cuddly plumpness. She might even have quite a prominent belly, which is due to her lack of muscle tone and not an indication of fat. Her muscle tone will develop as she grows older.

Your baby will have lost a lot of her plumpness as she grew taller, but her stomach may still be protruding a bit.

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