The two operations were conducted on unborn children with spina bifida, a birth defect in which the backbone and spinal canal do not close before birth.
The operating team led by Martin Meuli, director of surgery at the hospital, conducted the two successful procedures in late 2010 and the middle of this year.
A particular challenge of this kind of surgical interventions is the fact that two distinct patients, the mother and the foetus, have to be anaesthetized, monitored and operated on simultaneously.
Up to now, these types of operations have only been conducted in the United States, and the mothers there suffered no serious complications although the risk of premature birth was increased.
Still, according to an American study, these kinds of operations to correct spina bifida are more successful when conducted before the birth.
Doctors say the chances are greater that a child with this condition will have better motor function in his or her legs and improved ambulatory ability later if corrective surgery takes place in the womb rather than waiting until after the baby has been delivered.