Bicuspid Aortic Valve

The bicuspid aortic valve is the most common congenital heart valve defect.

During development in the womb, two of the three valve leaflets grow together, typically the left and right coronary leaflets. 1.3% of all newborns have this form of congenital aortic valve malformation.

https://en.wikipedia.org/wiki/Bicuspid_aortic_valve _([1])