Fetal Endoscopic Tracheal Occlusion (FETO) for Severe Congenital Diaphragmatic Hernia

Inclusion Criteria: * Maternal Age: 18-50 * Singleton gestation * Gestational age before 29 weeks 6 days * Severe left or right-sided CDH: For severe left sided CDH observed-to-expected lung-to- head ratio (o/e LHR) less than 25% between 22 and 29 6/7 weeks' gestation, liver herniation, MRI lung volumes less than 30% expected based on gestational age nomograms. For severe right sided CDH o/e LHR less than 30 % between 22 and 29 6/7 weeks' gestation, liver herniation, MRI lung volumes less than 30% expected based on gestational age nomograms. * Normal genetic karyotype or microarray testing by amniocentesis or chorionic villus sampling (CVS) * Absence of associated fetal structural cardiac anomalies by a dedicated fetal echocardiogram * Absence of other structural anomalies by ultrasound or MRI * Appropriate multi-disciplinary counseling performed with maternal-fetal medicine, neonatology, pediatric surgery, genetics, pediatric otolaryngology (ENT). * Must be willing to remain near LPCH Stanford (within 30 minutes from the hospital) for the duration of the balloon placement. * No maternal and/or fetal contra-indications to fetal surgery such as a bleeding disorder, poorly controlled diabetes or hypertension, short cervix (measuring \< 20mm), risk for preterm birth etc. * Planned pregnancy surveillance at LPCH Stanford * Planned delivery at LPCH Stanford * Able to provide written consent * Willingness to comply with all study procedures and availability (meets psychosocial criteria) for the duration of the study including having a support person Exclusion Criteria: * Contraindications to fetal surgery including poorly controlled hypertension, diabetes or other maternal medical condition including hematological disorder * High risk for preterm labor and/or delivery based on either significant history of preterm birth, short cervix (measuring \< 20mm), significant uterine anomaly or other risk factor, incompetent cervix (requiring cerclage) * Non-isolated CDH - CDH with additional structural anomalies * Significant maternal obesity defined as a body mass index (BMI) greater than 40. BMI is a calculation which includes a person's height and weight * History of natural rubber latex allergy * Uterine anomaly such as large or multiple fibroids or mullerian duct abnormality * Participation in another intervention study that influences maternal and fetal morbidity and mortality. * Bilateral CDH, left-sided CDH with O/E LHR \>25%, or left-sided CDH with O/E LHR \<25% but liver completely down in abdomen * Right-sided CDH O/E LHR \>30% or right-sided CDH with O/E LHR \<30% with liver completely down in abdomen * Significant placental abnormalities (abruption, chorioangioma, accreta) known at the time of enrollment and/or surgery * Maternal-fetal Rhesus isoimmunization, Kell sensitization or neonatal alloimmune thrombocytopenia, affecting the current pregnancy. * Maternal HIV, Hepatitis B with positive surface antigen, Hepatitis C with presence of virus in maternal blood due to risk of fetal transmission during the procedure * No safe or feasible fetoscopic approach to balloon placement.