I personally have no experience of this condition, so hopefully someone else will come along with more info. Here's what I found on the emedicine web site:
Mortality/Morbidity: Morbidity and mortality resulting from diaphragmatic disorders are associated with the etiology of the dysfunction. Individuals with anatomic defects are much more likely to survive than individuals with unresolving defective or absent neurologic impulses. Persons with unilateral dysfunction are much more likely to remain asymptomatic when compared with individuals with bilateral involvement.
Patients with neurologic involvement generally recover if dysfunction is not due to neuropathic process. Recovery can take up to 2 years or longer.
Patients with anatomic defects generally do well once the defect is repaired. The outcome of neonates with congenital diaphragmatic hernias generally relates to the pulmonary development after repair of the hernia.
Patients with congenital diaphragmatic hernias generally present in the neonatal period and have a mortality rate of 45-50%. The morbidity and mortality associated with congenital diaphragmatic hernias relate mostly to hypoplasia of the lung on the affected side. Thus, timely diagnosis and proper management remains the key ingredient to survival.