Kielgass won her first major title in 1985 in the East German 4×100 m relay team at the World Championships.

She also won as a member of the 4×200 m relay teams in the 1991 and 1998 World Aquatics Championships.

In the 200 m freestyle at the 1992 Summer Olympics, Kielgass won the bronze medal.

In the 4×100 m freestyle relay at the 1992 Summer Olympics, she was a member of the team in the heats but did not take part in the final, in which Germany won the bronze medal.

In the 4×200 m freestyle relay at the 1996 Summer Olympics, she was a member of the German team who won the silver medal, and in the 4×200 m freestyle relay in the 2000 Summer Olympics, she was a member of the German team who won the bronze medal.