RecruitingDevice studyTrial of FETO for Severe Congenital Diaphragmatic HerniaThis is a single site pilot trial to study the feasibility of Fetoscopic Endoluminal Tracheal Occlusion (FETO) therapy in the most severe group of fetuses with congenital diaphragmatic hernia (CDH) at Ann \& Robert H. Lurie Children's Hospital of Chicago (Lurie Children's). This procedure aims to increase fetal lung volume before birth and improve survival after birth. This study will enroll 10 pregnant women who meet study criteria.