Prenatal Intervention for Congenital Diaphragmatic Hernia
Congenital diaphragmatic hernia (CDH) is typically diagnosed at the second trimester screening US examination. Initial antenatal counselling and prognostication is essentially based on the presence or absence of additional structural or genetic anomalies and the degree of pulmonary hypoplasia and intrathoracic liver herniation by two dimensional (2D) ultrasound (US) and magnetic resonance imaging (MRI). In fetuses with moderate (observed-to-expected lung-to-head ratio [o/e LHR] of 25-35% or 35-45% with intrathoracic liver herniation) or severe (o/e LHR < 25%) CDH, prenatal intervention with tracheal occlusion to reverse pulmonary hypoplasia may be contemplated within the context of the ongoing international randomized controlled trial (RCT) (Tracheal Occlusion to Accelerate Lung Growth [TOTAL] Trial), as preliminary evidence seems to suggest an improvement in survival and morbidity particularly in severe CDH. Recent advances in minimally invasive techniques have made it possible to achieve percutaneous fetal endoscopic tracheal occlusion (FETO) therapy through a 3-mm access port with local anesthesia alone. An endoluminal balloon is inserted into the trachea with sonoendoscopic guidance at 26-28 weeks for severe CDH and 30-32 weeks for moderate CDH with reversal of tracheal occlusion at 34 weeks. Response to therapy may be predicted by o/e LHR prior to intervention, and pulmonary and vascular indices post procedure. However, further standardization is required in prenatal prognostication indices in fetuses conservatively managed and those undergoing fetal intervention. Although preliminary observational studies appear to be promising, FETO comes with a significant risk of preterm premature rupture of membranes (PPROM) and preterm delivery. It is anticipated that the TOTAL trial will provide insight into many of these clinical questions regarding the antenatal management of moderate to severe CDH and the role of fetal intervention. Furthermore, delivery of infants in experienced paediatric CDH centers with standardized clinical care pathways for postnatal management are necessary to optimize perinatal outcomes. Additional data are required to evaluate long-term morbidities in CDH survivors, particularly in the era of fetal therapy. Additional prenatal therapeutic options, such as sildenafil and miRNA warrant further investigation, and may prove to be promising non-invasive therapeutic antenatal approaches.
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