Twenty week old foetus Coloured ultrasound scan of a week five month old human foetus in side view The head is at right seen in profile facing upwards The torso is at lower centre with vertebrae of the spine seen A hand is visible above the torso and a leg is at left The crown rump length sitting height of a foetus at weeks is about centimetres and its weight about grams Growth in length is particularly striking during the rd th and th months The foetus is covered with fine hair called lanugo eyebrows and head hair have also developed and movements of the foetus are felt by the mother