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-expectedlung-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 agenomograms. For severe right sided CDH o/e LHR less than 30 % between 22 and 29 6/7weeks' gestation, liver herniation, MRI lung volumes less than 30% expected based ongestational age nomograms.

• Normal genetic karyotype or microarray testing by amniocentesis or chorionic villussampling (CVS)

• Absence of associated fetal structural cardiac anomalies by a dedicated fetalechocardiogram

• 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 bleedingdisorder, 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 psychosocialcriteria) 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 ofpreterm birth, short cervix (measuring < 20mm), significant uterine anomaly or otherrisk 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. BMIis 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 fetalmorbidity 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 livercompletely down in abdomen

• Significant placental abnormalities (abruption, chorioangioma, accreta) known at thetime of enrollment and/or surgery

• Maternal-fetal Rhesus isoimmunization, Kell sensitization or neonatal alloimmunethrombocytopenia, affecting the current pregnancy.

• Maternal HIV, Hepatitis B with positive surface antigen, Hepatitis C with presenceof virus in maternal blood due to risk of fetal transmission during the procedure

• No safe or feasible fetoscopic approach to balloon placement.