Watch This: A Twist On The Doppler Effect Opens New Vistas On Tiny Hearts

Surgeons need steady hands. If you’re Wolfgang Arzt, you also need nerves of steel.
Arzt performs heart surgery on unborn babies, inserting a needle into the mother’s womb and carefully pushing it through a tiny valve in the fetus’ heart that’s just 2 millimeters in diameter, or about as wide as a pinhead. Then he perforates the valve. “If I go 1 or 2 millimeters too far, I tear off the vessel and everything is over,” he says from his office at Kepler University Hospital in Austria, where as head of prenatal care he has overseen more than 140 such procedures.