Baby’s development in the first trimester

Learn about how your baby’s brain develops and changes each month in the first trimester.

Month 1:

  • Baby’s journey has begun.
  • Their heart is already growing.
  • Baby’s brain and spinal cord start to grow.
  • The brain starts making lots of neurons (connections in the brain). Some neurons can already connect to each other. This means baby’s brain can tell the body to do some movements, like curling up.
  • Baby is the size of a native millet seed or sesame seed (around 1mm).

Month 2:

  • An ultrasound can pick up baby’s heartbeat.
  • Baby’s head, eyes and ears have grown.
  • Baby’s brain forms its main parts.
  • Baby is about the size of an apple seed (around 1.75mm).

Month 3:

  • Baby increases in size by 10 times this month and takes on a human shape.
  • Baby has all their organs plus arms, legs, hands, fingers, feet and toes.
  • Baby can open and close fists and mouth.
  • Baby can taste and smell. Baby may learn to prefer the taste of food mum eats.
  • Baby can control how they move because the spinal cord is formed.
  • Mum probably won’t feel baby yet.
  • Baby is about as long as a passionfruit (around 6.35cm).

Read about the second trimester.

Published — 20 February 2019 Last updated — 11 March 2019

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