Over the centuries, great interest has been devoted to the placenta and to its highly symbolic significance. The Renaissance represented the age of historical and cultural transition between classical and modern scientific paradigms. In the medical setting, Realdo Colombo represents one of the protagonists of this revolution. In his masterpiece, "De Re Anatomica", he revolutionized the former medical perspective. We present a passage from this book, which carries invaluable information on the Renaissance viewpoint on pregnancy and placental biology. The connections between Colombo's theories and the previous medical tradition are also analysed.