Until the seventies, it was nearly impossible to investigate inside the womb. Twenty years later, fascinating progress has been made.André Boué, who directs a research unity at the INSERM, has lived day by day the development of prenatal medicine. He recalls the steps of its history and teaches us about the actual knowledge of the foetus, the diseases which threaten it or those it carries in its genetic capital and which means of investigation and treatment are available today.