Prior to switching allegiances to Sweden in 1953, Birte Christoffersen won 17 Danish national titles in diving, an Olympic bronze medal in the platform event in 1948, and European Championship bronze medals in the 3 metre springboard and platform competitions from 1950. She also finished ninth among sixteen starters in the springboard tournament in 1948. From 1954 on, as Birte Hanson, she represented Sweden internationally, winning silver medals in the 3 metre springboard and platform events at the 1954 European Championships and bronze in the platform competition in 1958, as well as numerous titles in her adopted country. She also competed in two more editions of the Olympics, but did not reach the podium, finishing ninth and eight in the springboard and platform tournament respectively in 1956 and 12th among 18 participants in the platform event in 1960. She retired from active competition in the early 1960s but remained athletically active in her career as a physical education instructor in Malmö.