Tracheal Occlusion To Accelerate Lung Growth (TOTAL) Trial for Severe Pulmonary Hypoplasia

Inclusion Criteria: * Patients aged 18 years or more, who are able to consent * Singleton pregnancy * Anatomically and chromosomally normal fetus * Left sided diaphragmatic hernia * Gestation at randomization prior to 29 wks plus 5 d (so that occlusion is done at the latest on 29 wks plus 6 d) * Estimated to have severe pulmonary hypoplasia, defined prenatally as: O/E LHR \<25 %, irrespective of the liver position * Acceptance of randomization and the consequences for the further management during pregnancy and thereafter. * The patients must undertake the responsibility for either remaining close to, or at the FETO center, or being able to travel swiftly and within acceptable time interval to the FETO center until the balloon is removed. * Intended postnatal treatment center must subscribe to suggested guidelines for "standardized postnatal treatment". * Provide written consent to participate in this RCT Exclusion Criteria: * Maternal contraindication to fetoscopic surgery or severe medical condition in pregnancy that make fetal intervention risk full * Technical limitations precluding fetoscopic surgery, such as severe maternal obesity, uterine fibroids or potentially others, not anticipated at the time of writing this protocol. * Preterm labour, cervix shortened (\<15 mm at randomization) or uterine anomaly strongly predisposing to preterm labour, placenta previa * Patient age less than 18 years * Psychosocial ineligibility, precluding consent * Diaphragmatic hernia: right-sided or bilateral, major anomalies, isolated left-sided outside the O/E LHR limits for the inclusion criteria * Patient refusing randomization or to comply with return to FETO center during the time period the airways are occluded or for elective removal of the balloon