Balloon in the womb could save babies with rare birth defect

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * 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 persons age 18 years and older * Singleton pregnancy * Absence of life-limiting genetic anomalies on microarray or karyotype on amniocentesis. Results by fluorescence in situ hybridization (FISH) will be acceptable if the patient is \> 26 weeks gestation * Fetal echocardiogram with changes expected with CDH and no major structural cardiac defects (small ventricular septal defect (VSD)/atrial septal defect (ASD) may be included as they will not alter outcome and are not life-limiting) * Left or Right CDH with liver up without presence of concomitant life-limiting anomalies. * Gestational age for Left-CDH at enrollment prior to 29 weeks plus 6 days for O/E LHR \<30%; for Right-CDH with O/E LHR \<45% gestational age at enrollment prior to 29 weeks plus 6 days. * Meets psychosocial criteria * Willing to reside within 30 minutes of Children's Mercy Hospital Fetal Health Center and ability to maintain follow up appointments * Patient has a support person (e.g. spouse, partner, friend, or parent) that is available to stay with her for the duration of the pregnancy. * Willing to comply with restrictions of daily living including inability to exercise, have intercourse or return to work. Exclusion Criteria: * Pregnant persons \< 18 years of age * Multi-fetal pregnancy * Rubber latex allergy * History of preterm labor, cervix shortened (\<15mm at enrollment or within 24 hours of FETO balloon insertion procedure) or uterine anomaly strongly predisposing to preterm labor, placenta previa * Psychosocial ineligibility precluding consent: * Inability to reside within 30 minutes of Children's Mercy Hospital Fetal Health Center until balloon removal or delivery (if clinically indicated) * Patient does not have a support person (e.g., spouse, partner, parent) available to stay with the patient until balloon removal or duration of the pregnancy (if clinically indicated) * Adult unable to consent * Prisoners * Social work or health psychology will meet with each patient to evaluate the social situation and support system. Identifiable issues of social instability or compliance with the protocol will exclude the patient as a potential candidate. * Bilateral CDH, isolated left-sided with O/E LHR ≥30% (measured at 18 weeks 0 days to 29 weeks 5 days) as determined by ultrasound, isolated right-sided CDH with O/E LHR ≥45% (measured at 18 years 0 days to 29 weeks 5 days) as determined by ultrasound. * Additional life-limiting fetal anomaly by ultrasound, MRI or echocardiogram that may affect outcome. These include chromosomal or anatomic abnormalities, associated anomalies recognized to alter survival prognosis (i.e., CDH and severe congenital heart disease) or presence of an underlying genetic syndrome (e.g., Fryns). No cases will be removed post hoc if abnormalities are discovered in the course of post-operative monitoring. * Patient contraindication to fetoscopic surgery or severe medical condition in pregnancy * History of incompetent cervix with or without cerclage * Placental abnormalities (previa, abruption, accreta) known at the time of enrollment * Pregnant person-fetal Rh isoimmunization, Kell sensitization or neonatal alloimmune thrombocytopenia affecting the current pregnancy * Pregnant person tests positive for HIV, Hepatitis-B, Hepatitis-C. Due to of the increased risk of transmission to the fetus during maternal-fetal surgery the patient must test negative for these conditions prior to enrollment. * Uterine anomaly such as large or multiple fibroids or mullerian duct abnormality * There is no safe or technically feasible fetoscopic approach to balloon placement * Participation in another intervention study that influences maternal and fetal morbidity and mortality or participation in this trial in a previous pregnancy. * Patient refusal to receive blood products * Additional major anomaly or abnormality that would prevent successful FETO, per discretion of the Principal Investigator