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Can fetal ultrasound and MRI predict outcome after fetal endoscopic tracheal occlusion for isolated severe congenital diaphragmatic hernia?

Congenital diaphragmatic hernia (CDH) is a severe congenital anomaly that occurs in approximately 1 in 2500 live birth, accounting for 8% of overall fetal malformations. CDH may be associated with other congenital anomalies in 40% of cases, leading to worse prognosis. While the mild and moderate forms of isolated CDH have favorable prognosis, the severe forms of CDH are associated with high perinatal mortality and morbidity due to severe pulmonary hypoplasia and severe pulmonary arterial hypertension. Although the disease can be treated by neonatal surgery in surviving infants, mortality rate remains high and of the order of 75%, especially for severe forms. The prenatal ultrasound is important not only to confirm the diagnosis but also to evaluate the prognosis, by calculating the so-called lung area-to-head circumference (LHR) in fetuses with CDH, and by comparing to healthy fetuses LHR in order to obtain the observed-toexpected LHR (o/e-LHR). When an o/e-LHR < 15% is observed, then an extremely severe CDH is diagnosed, representing 1% of all CDH patients, with a mortality rate higher than 60%–70%. If an o/e-LHR between 15% and 25% is observed, then we are facing a severe form of CDH, representing 14% of the CDH fetuses, with a mortality rate higher than 50%–60%. Values of o/e-LHR in the range of 25%–36% are classified as moderate type of CDH, with expected good survival rate. Another prenatal parameter that is significantly associated with prognosis is the liver herniation, so called “liver-up”. The amount of liver herniation into the fetal chest can be evaluated by fetal ultrasound and MRI, and studies have demonstrated that both the amount of liver herniation and fetal lung sizes could be used together as independent factors to predict prognosis (mortality and need for ECMO). Werneck Britto et al. evaluated the amount of liver herniation by calculating the ultrasound liver area-to-thoracic area ratio (US-LiTR) comparing to the MRIliver volume-to-thoracic volume (MRI-LiTR). These investigators demonstrated that first there was good correlation between US-LiTR and MRI-LiTR (r = 0.87; P < 0.001), and that both ratios were significantly associated with mortality and the need for ECMO (P < 0.01). The investigation about the feasibility and effectiveness of fetal surgery for CDH started in the 80's, and has considerably progress. Now, the procedure is usually performed with local maternal skin anesthesia, mild fetal anesthesia and the introduction of a tiny telescope of 1.3 mm into the amniotic cavity, fetal mouth, and fetal trachea. Inside the fetal trachea, a detachable balloon is inflated and left there from 26 to 28 weeks' gestation to approximately 34 week's gestation. Some studies suggest even to perform an early tracheal occlusion at around 24 week's gestation based on the embryological development of the lungs. In 2021, the TOTAL-trails (Tracheal Occlusion to Accelerate Lung Growth) conducted as intention-to-treat analysis, randomized controlled trials, that included 80 mothers, drawn firm conclusions: FETO does not improve survival rate in moderate CDHs, whereas FETO improves significantly the postnatal survival rate in isolated severe left-sided CDH (survival to discharge and survival to 6 months from 15% in the expectant care group vs. 40% in the treatment arm), supporting a previous study. As clinically expected, the enhanced percentage of infants surviving, either to discharge from neonatal intensive care unit (NICU) and to 6 months were at the expensive of a higher rate of preterm premature rupture of membrane (pPROM) and with premature delivery. The current observation by Dr. Ruano's team in the present issue of the Journal of Clinical Ultrasound has been carried out in seven fetuses undergoing FETO procedure at a mean gestational age of 28.5 ± 0.5 weeks. Longitudinal ultrasound examinations were performed to evaluate fetal lung development/response after FETO. Received: 4 December 2021 Accepted: 6 December 2021