**2.2.2 Pulmonary atresia**

During pregnancy the oxygen necessary is not supplied through the fetal lungs but by the placenta. The Foramen Ovale is an opening between the right and the left atrium, that allows blood to pass by the ventricles. After birth this opening is usually closed. Pulmonary Atresia is a malfunction that may appear during pregnancy: it is an incorrectly developed pulmonary valve. Instead of a valve there is just a membrane. Thus no blood supply to the lungs is possible, and this causes the death of newborns when oxygen supplied by the placenta is not supplied anymore. Pulmonary atresia occurs in about one out of every 20,000 live births. (Daubeney et al., 2005) (Litovsky et al., 2005)

Anatomic obstruction to the right or left ventricular outflow tract may cause ventricular dysfunction, can divert fetal blood flow in the uterus and result in cardiac chamber hyperplasia. Thus severe aortic or pulmonary stenosis can result in a hypoplastic left or right ventricle with an inability for the ventricular chambers to support the systemic or pulmonary circulation. Theoretically early relief of the fetal aortic or pulmonary stenosis may prevent such occurrence and might preserve the right or left ventricular function .

Pulmonary atresia can be diagnosed in the 12-14th week of gestation. The surgical intervention should be performed as soon as possible. In the 14th week the fetus size is about 9-14cm and has a weight in the range of 60 - 200g. In this development stage the pulmonary membrane has a diameter of approximately 1mm.

In the case of pulmonary atresia an early surgical intervention is the only alternative to abortion and could allow normal development of the pulmonary valve and the right ventricle. A suitable surgical procedure for the treatment of pulmonary atresia is by accessing the right ventricle with a steerable micro catheter, identifying the pulmonary valve/membrane and then perforating it. However one must consider that tissues in this early development state are very fragile and can be damaged easily, thus haptic force feedback is a important safety feature in order to avoid to damage to the vessels or the heart when navigation the catheter, which would be life threatening for the fetus.
