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 know 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 sex organs (male or female) have formed
- Your baby has started to kick (you can’t feel it yet)
- Your baby sucks his 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 she’s 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
- Your baby’s hair and eyebrows begin to grow
- Your baby’s fingernails and toenails have developed
- Your baby’s taste budgs and inner ears have formed (she 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 she’s 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 her skin. It will also help her pass through your birth canal
- Your baby kicks, twists and turns. She 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 she’s 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 him 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 to sing to him
- Your immunity to some diseases is being passed to your baby to protect him 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 ready to be born after 37 weeks
- Your baby’s skin is pinker and becomes less wrinkled as he gains weight
- Your baby’s lungs are ready to breathe air after 37 weeks
- Your baby has less room to move, so his movements will feel different. Ask your healthcare provider for more information about your baby’s movements
- Your baby may scratch himself with his own fingernails