After qualifying, she served in the
Royal Army Medical Corps, rising to the rank of captain. She completed her training at
Glasgow Royal Infirmary and Western General Hospital. She worked in
Sheffield and Edinburgh before moving to
Aberdeen in 1958 with her husband when he took up the position of
Regius Professor of
Materia medica at the
University of Aberdeen. In 1960, Macgregor became a research assistant in
Sir Dugald Baird's department of midwifery and gynaecology at the university and worked with his team to establishing a trial screening programme for cervical cancer. Macgregor took exfoliated cell smears using the
Papanicolaou stain, interpreted them, and trained the team in the technique. In 1963, she received an MD by thesis for her work. In an article in the
British Medical Journal co-authored by Macgregor and Baird they stated that cervical cytology has now passed beyond the experimental stage' and that cervical cancer could largely be prevented by cytological detection and treatment of a pre-invasive stage. Having seen the effects of cervical cancer in practice Macgregor took the findings of research and put them into practice, encouraging women to undergo screening. She spoke with general practitioners, convincing them that their patients should be screened. She and the team at the university kept records of the screenings, and she collaborated with statisticians to evaluate the effectiveness of screening. Within 5 years of the screen servicing being established there was a significant decrease in cervical cancer in the Aberdeen area. Such was the success of the programme in Aberdeen that it led to cervical screening services being introduced throughout the UK. The research and programme were recognised worldwide, leading to the development of cervical screening all over the world. Macgregor retired from the University of Aberdeen in 1985. She continued to work part-time as Director of Harris Birthright Research Centre in Aberdeen. Macgregor always suspected that cervical cancer was caused by an infection, and during her lifetime
human papillomavirus was found to be the agent. The
vaccine for the virus was announced on the same day that she died. == Awards and honours ==