Fetal development week by week
Up to 20 weeks the fetus is measured from crown (top of the head) to rump (bottom). From 20 weeks onwards the fetus is measured from head to heel.
The feet are around 2mm long. Body muscles are almost developed. Ears and nose can now be seen. Starts to move around although too small to feel it.
Taste buds start to develop as well as tooth buds. The heart is almost completely developed and the brain is growing fast. Can stick out tongue and suck.
The feet are around 1cm long. Fingernails and toenails start to appear. Can suck thumb and get hiccups. Heart rate can be up to 160 a minute which is double that of a healthy adult.
Can open and close its mouth. Bone starts to replace cartilage, and ribs begin to appear. The unique fingerprint is already developed.
Ears are fully developed. First hair – head and eyebrow hair develop. Eyes move towards the centre of the face.
Taste buds are now fully developed. Can move arms and make a fist. Legs longer than arms and body now larger than head.
Baby hears external voices, sleeps and dreams. Grasps with hands and can kick. Facial muscles are more developed so first expressions appear like frowning.
Retina is now sensitive to light.
Recognisable active and resting periods now. Can hear external sounds and be startled by loud noises.
Scalp hair has sprouted and continues to grow.
Can recognise the mother’s voice. Skin is getting thicker. Senses start to develop at this time with specialised areas of the brain for each sense.
27cm head to heel
The bone marrow starts to make blood cells. Weight is steadily gained.
Regular sleeping and waking periods and mother’s movements can wake the baby. Baby reacts to loud noises.
Baby can successfully suck. Eyebrows are now visible and skin pigment is forming.
Eyelids now clearly visible. Baby can react to strong or bitter flavours eaten by the mother.
Hands now fully developed and dexterity improving. Brain growing fast. Baby touches hands to face, hand to hand and foot to leg.
Baby’s eyes start to open around this time. Feet now around 5cm long.
Eyes can now open, close and blink. Head now over 7cm diameter.
Milk teeth start developing under the gums. Eyes start to move in the sockets. Feet around 5.5cm long.
Can respond to pain. The brain is developing millions of neurons.
The baby can now control its own body temperature. Wrinkled skin starts to smooth out.
Eyes now respond to light and darkness.
The baby sleeps most of the day at this stage. Toenails and fingernails are now completely formed.
Head diameter is now around 8.5cm
Fat is building up, plumping out the arms and legs.
Lungs are almost fully developed.
The baby is growing rapidly. Head diameter is now on average over 9cm.
Development is now complete. The baby continues to gain weight.
Generally now in the final birth position.
Head around 10cm diameter.
Disclaimer This is for general information only and any concerns should be directed to a medical practitioner.
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