Throughout his anatomical career Leonardo strove for objectivity. But here, in the best known of his anatomical drawings, he makes striking use of red chalk under dense curving pen lines to evoke the coiled potential of the child in the womb. Leonardo was puzzled by the manner in which a full-term baby could fit into the uterus. Although he may have dissected a miscarried foetus and a woman who had died in childbirth, his drawings of the posture of the foetus are mainly based on guesswork. But modern imaging techniques confirm that Leonardo’s intuitions were essentially correct.