Foetal genitalia at 10 weeks. At this stage of development, internal sexual difference takes place but external differences are not yet obvious. Overall, the crown-rump length (sitting height) of the foetus is 3-4.5 centimetres and it weighs around 35 grams. The face has become more human; lips, eyelids and external ears have formed. Fingers and toes are visible. Foetal movements begin at this time, but are not usually felt by the mother.