Eight week old foetus. Illustration of a human foetus in side view, 8 weeks old, in the womb. It has a human-like appearance and is seen surrounded by the inner amnion membrane. Blood vessels of the placenta (at left) are linked to the foetus by an umbilical cord. At lower left is the yolk sac (yellow). The foetal head is large, with eyes, ear auricle, and the long limbs have differentiated toes and fingers. The genital organs develop at 7 weeks, and the male sex of this foetus is evident. At this stage the foetus is about 30 mm long (crown-rump length) and under 10 grams in weight. Most organs have formed, but require growth. After the eighth week the embryo becomes a foetus.