During the nine months of pregnancy your baby will go through many changes.

First trimester

0-4 Weeks

  • Your baby is called an embryo and is about 0.6 cm (1/4 inch) long or about the size of a grain of rice.
  • The embryo sticks to (implants in) the wall of your uterus
  • The placenta, amniotic sac and fluid begin to form
  • The early structures of the brain have started to form
  • You may notice that your period will be late

5-8 Weeks:

  • The embryo is about 2.5 cm (1 inch) long and weighs less than a grape
  • The heart starts beating
  • The head and brain are taking shape
  • Internal organs are forming
  • Teeth begin to develop
  • Arm and leg buds are beginning to show
  • The spine starts to show and bones begin growing
  • The spinal cord starts to develop nerve connections (synapses) that will allow your baby to move his limbs and fingers, hiccup, stretch and yawn

9-13 Weeks:

  • Your baby is now called a fetus, is about 7.6 cm (3 inches) long and weighs about as much as a tube of lipstick
  • The eyes, ears and nose have formed
  • The mouth has formed, with lips, tongues and tooth buds
  • The hands, fingers and fingerprints, knees, ankles and toes have formed
  • The reproductive organs have formed
  • Your baby has started to kick (you can’t feel it yet)
  • Your baby sucks their thumb and makes breathing motions
  • At around 12 weeks you may be able to hear your baby’s heartbeat through a fetal doppler
  • Your baby’s basic brain cells (neurons) are developing very quickly, becoming more organized and are starting to connect to each other

Second trimester

13-18 Weeks:

  • Your baby is about 12.5 cm (5 inches) long (curled up, they are about the size of a tennis ball)
  • Your baby weighs about 90g (3 oz)
  • Your baby is starting to look more like a real baby
  • Your baby’s body is covered with lanugo (fine hair)
  • Your baby’s hair and eyebrows begin to grow
  • Your baby’s fingernails and toenails have developed
  • Your baby’s taste buds and inner ears have formed (they can hear you too!)
  • Your baby can roll over within the uterus

19-22 Weeks:

  • Your baby will grow up to 18 cm (7 inches) during these 4 weeks. By the end of 22 weeks they are about 25 cm (10 inches) long (about the distance from your elbow to your wrist)
  • Your baby weighs about 250g (8-9 oz)
  • Your baby is covered with a protective cream (vernix) that helps to conserve heat and moisturize their skin. It will also help them pass through your birth canal
  • Your baby kicks, twists and turns. They may be most active when you are sitting still
  • Your baby can grasp and suck
  • Brain cells are continuing to develop more connections with each other
  • By 20 weeks your baby’s brain and nervous system is developed enough to react to sound and light

23-26 Weeks:

  • Your baby is now about 32 cm (13 inches) long (roughly the distance from your elbow to your fingertips)
  • Your baby weighs around 1kg (2 lbs) or as much as a small melon
  • Your baby moves around. You can feel when they are high up in your abdomen or low down in your pelvis
  • Your baby has finger and toe prints
  • Your baby will develop a pattern of sleep and activity
  • Your baby can hiccup
  • Your baby’s lungs aren’t yet fully developed
  • Your baby’s eyelids can open and close
  • Your baby is growing, but looks skinny
  • Your baby’s brain stem (which controls heart rate, breathing, blood pressure and other vital functions) is now developed

Third trimester

26-31 Weeks:

  • Your baby is about 38 cm (15 inches) long
  • Your baby weighs about 1kg (2-3 lbs), or as much as a small bag of sugar
  • Your baby will be moving a lot. Other people will be be able to see and feel them moving too
  • Your baby’s eyes open, and he has eyelashes and eyebrows
  • Your baby will sense light and sound
  • Your baby can tell when you’re moving
  • Most of your baby’s billions of brain cells are formed
  • The outer part of the brain (cerebral cortex) continues to develop. The grooves and folds of the brain are formed.

32-35 Weeks:

  • Your baby is about 46 cm (18 inches) long
  • Your baby weights 2.25-2.5 kg (5-5.5 lbs), or as much as a small bag of flour
  • You might feel your baby’s heels or elbow sticking into your ribs
  • Your baby is building up layers of fat under the skin that will provide warmth after birth
  • Your baby’s brain is growing quickly now. Talk and sing to them
  • Your immunity to some diseases is being passed to your baby to protect them during the first few months
  • The soft hair on your baby’s body is going away

36-40 Weeks

  • Your baby is about 55 cm (20 inches) long
  • Your baby weights 2.7 – 4 kg (6-9 lbs)
  • Your baby may be gaining 28g (1 oz) a day
  • Your baby is not considered pre-term if they are born after 37 weeks
  • Your baby’s skin is pinker and becomes less wrinkled as they gain weight
  • Your baby’s lungs are ready to breathe air after 37 weeks
  • Your baby has less room to move, so movements will feel different to you. Ask your healthcare provider for more information about your baby’s movements
  • Your baby may scratch their face with their fingernails