Congenital diaphragmatic hernia (CDH) is associated high mortality and morbidity, mainly in those cases with severe forms where there are extremely reduced lung volumes, liver herniation and decreased abnormal pulmonary vascularization. Fetal endoscopic tracheal occlusion performed between 26 and 30 weeks (standard FETO) has been shown to increase fetal pulmonary size and vascularity, and to improve infant survival in isolated severe CDH. Fetal pulmonary response followed FETO can be used to predict outcome and is dependent on the size of the fetal lung prior to the procedure.

We hypothesize that performing an earlier FETO, between 22-24 weeks, fetuses with severe form of CDH will have a better fetal pulmonary response and higher chance of surviving.

We pretend to investigate if "early FETO" will improve the survival rate and the fetal pulmonary response, by conducting a randomized controlled trial comparing the results with those fetuses that undergo to "standard FETO" (between 26-28 weeks).

Inclusion Criteria:

• Fetuses with isolated congenital diaphragmatic hernia (normal fetal karyotype and absence of any associated structural anomaly);
• Gestational age established by last menstruation and/or first trimester ultrasonography;
• Prenatal diagnosis of congenital diaphragmatic hernia before 24 weeks of gestation
• Severe congenital diaphragmatic hernia (at 24 weeks, lung-to-head ratio <1.0 and at least 1/3 of the liver herniated into the fetal thorax)
• written informed consent (by the patient)

Exclusion Criteria:

• Preterm premature rupture of the membranes before randomization
• Preterm labor before randomization