Congenital diaphragmatic hernia is an anatomically simple birth defect in which contents of the fetal abdomen migrate into the chest due to incomplete formation of the diaphragm. Herniation of viscera into the chest prevents the fetal lungs from developing and growing to normal size. In the most severe cases, there is significant morbidity and mortality at birth. For these fetuses, fetal intervention may improve outcomes by enabling the lungs to grow enough in utero that they are capable of sustaining life after birth. This unblinded, non-randomized trial will assess the safety and efficacy of the use of the Goldvalve balloon and MiniTorquer microcatheter to perform percutaneous temporary tracheal occlusion to treat severe CDH in utero. The primary outcome variable will be fetal lung growth due to successful 'plugging/unplugging' of the trachea, as determined by serial lung-head ratio (LHR) measurements. Secondary outcome variables include maternal, fetal and neonatal variables, specifically neonatal survival at 90 days of life. For infants who survive beyond 90 days post-delivery, their families will be offered follow-up (up to 2 years of age and possibly beyond) in the Long-term Infant-to-Adult Follow-up Evaluation (LIFE) Clinic at UCSF.

General subject population: Pregnant women in the second trimester, at least 18 years of age, and of any and all ethnic backgrounds.

Inclusion Criteria:

• Confirmed diagnosis of CDH
• Normal fetal echocardiogram
• Normal karyotype
• Fetal liver herniated into the left hemithorax
• Lung-head ratio (LHR) is 1.0 or less, calculated between 24-26 weeks' gestation
• Fetus is between 26 and 28 weeks' gestation
• Singleton pregnancy
• Mother meets psychosocial criteria
• Pre-authorization from third-party payor for fetal intervention, or ability to self-pay.

Exclusion Criteria:

• Failure to meet all inclusion criteria
• Other congenital anomalies detected on ultrasound
• Contraindication to abdominal surgery or general anesthesia
• Allergy to latex
• Preterm labor, preeclampsia, or uterine anomaly (e.g., large fibroid tumor)
• Family unable or refuses to stay in San Francisco for duration of the tracheal occlusion period and for the duration of the pregnancy as medically necessary.