Comprehensive fetal evaluations will be completed at the Johns Hopkins Center for Fetal Therapy to confirm eligibility. This includes an ultrasound, magnetic resonance imaging, a fetal echocardiogram and fetal genetic studies to identify cases with isolated CDH. Once eligibility is confirmed, participation for FETO treatment will be offered. The voluntary nature of participation will be stressed throughout. Willingness and logistics of the participant to remain under supervision of the Center for Fetal Therapy at the Johns Hopkins Hospital, while the fetal airway is occluded will also be discussed in detail. Informed written consent will be obtained prior to any study related procedures.