When an unborn baby has a hole in the diaphragm (congenital diaphragmatic hernia or CDH), organs from the abdominal cavity can move into the chest cavity. As a result, the lungs do not have enough space to develop properly, which can make it difficult for the baby to breathe after birth and may even lead to death.
In severe cases of CDH, doctors insert a small balloon into the unborn baby’s windpipe during pregnancy via keyhole surgery. This balloon retains fluid in the lungs, allowing them to grow more effectively. UZ Leuven Leuven is known around the world for this FETO-techniek, which was co-developed in Leuven by an international research team led by UZ Leuven and KU Leuven. The treatment increases the survival rate for severe CDH from around 15 to 40 per cent.
Additional surgery increases risks
But the balloon needs to be removed again prior to birth. Until now, this has been done by means of a second surgical procedure, usually around 34 weeks into the pregnancy. If this does not happen in time, the baby will be unable to breathe after birth. This procedure carries further risks, such as premature rupture of the membranes and preterm birth. Furthermore, around one in three pregnant women go into labour spontaneously whilst the balloon is still present. In such cases, doctors must remove the balloon as a matter of urgency, before the baby is born.
As the procedure on unborn babies is only carried out in specialist centres, expectant mothers often stay near the hospital for weeks at a time. In 2025, around two-thirds of the patients treated came to UZ Leuven from abroad for FETO treatment. This makes the period particularly difficult for families and, at the same time, requires specialist teams to be on call at all times.
From two surgical procedures to one
One minor modification to the balloon means that a second procedure is no longer necessary. Positioning the balloon remains the same, but inside there is a small magnetic ball that closes a valve. To deflate the balloon, the pregnant woman now simply walks around an MRI scanner. The magnetic field sets the ball into motion causing the valve to open and the balloon to deflate automatically. After the procedure, doctors use an ultrasound scan to check that the airway is completely clear. In the study, the balloon was successfully deflated in all cases. Thanks to this new ‘smart’ balloon, some of the follow-up care can be provided closer to home in future. This makes the process safer and less burdensome for families and care teams.
"This technique makes an existing treatment a lot simpler. We're replacing a surgical procedure by a smart balloon that we can deflate using an MRI scanner. This means fewer risks for the baby, less uncertainty for the parents and care that is easier to plan for the team.”
The study was carried out thanks to collaboration between multidisciplinary teams from Leuven and l’hôpital Antoine Béclère AP-HP, together with the developers of the SMART-TO-balloon at the Université de Strasbourg. The results were published in the journal The Lancet.
