Gertrude Jefferson (née Flumerfelt) was born in Winnipeg, Canada. She entered Manchester medical school, in 1907 and qualified MRCS LRCP in 1912. In 1913 she married the neurosurgeon Geoffrey Jefferson.
During the First World War she was in St Petersburg with her husband at the British Red Cross Hospital. After the war she settled with her family in Manchester and worked part-time in maternity and child-welfare centres. In 1937 she took the DPM and was appointed an assistant psychiatrist at MRI in 1939. In 1948 she started the Family welfare service. This was an innovative development, sponsored by Manchester Corporation's public health department, to offer preventive mental health treatment.