After graduation she worked as a registrar specialising in
obstetrics and gynaecology at
Simpson's maternity hospital, Edinburgh, under the supervision of Professor
Robert James Kellar. which has continued as a popular text for doctors working in the field - the fifth edition, edited by University of Edinburgh colleagues including
Professor Anna Glasier, was published shortly before she died. She was chairperson of the UK National Association of Family Planning Doctors, and held many other national medical roles. She was not afraid to challenge the establishment when the needs of women were threatened. In her time, the medical specialty of Family Planning has become firmly established in the UK, now known as the
Faculty of Sexual and Reproductive Healthcare. Loudon retired in 1988. == Awards and honours==