• Provision of signed and dated informed consent form

• Stated willingness to comply with all study procedures and availability (meets psychosocial criteria below) for the duration of the study

• Pregnant women, age 18 years and older

• Singleton pregnancy

• No pathogenic variants on microarray or pathologic findings on karyotype; results by fluorescence in situ hybridization (FISH) will be acceptable if patient is \>26 weeks

• Fetal echocardiogram with changes expected with CDH and no major structural cardiac defects

• Fetal CDH (left or right) with severe pulmonary hypoplasia, defined as o/e LHR \<25% with liver up

• Gestational age at FETO procedure: if o/e LHR \<25%, will be done at 27 weeks plus 0 days to 29 weeks plus 6 days

• Meets psychosocial criteria

‣ Willing to reside within 30 minutes of NewYork-Presbyterian Sloane Hospital for Women/Columbia University Irving Medical Center (CUIMC) and ability to maintain follow up appointments. NYP/CUIMC will work with the study participant to assist in securing housing 30 minutes from the hospital if this is a challenge to her.

⁃ Patient has a support person (e.g. spouse, partner, friend, parent) that is available to stay with her for the duration of the pregnancy near NewYork-Presbyterian Sloane Hospital for Women/Columbia University Irving Medical Center (CUIMC)

⁃ Willing to comply with restrictions of daily living including inability to exercise, have intercourse, or return to work