While in medical school, Sundquist and Nilsson experienced discrimination from faculty members who refused to give them higher marks than male students.

Graduating in 1900, the following January, Nilsson and Sundquist wrote a plea, signed by almost every woman doctor in the country, as well as many female medical students, protesting their inability to work even as paediatricians or on behalf of women patients, except in private practices.

[2] Simultaneously, from 1902 to 1918, she served as the physician at the private girls' Detthowska School [sv] and in 1903 began working at the Stockholm City Polyclinic specializing in sexually transmitted diseases.

From the end of 1903 until early 1904, she worked on the regulatory Committee for the Prevention of Infectious Sexually Transmitted Diseases and in 1904, was elected to membership of the newly established Dermatological Society.

[1] That year, wanting both to control immoral behaviour and address the declining birth rate in the country, the Riksdag passed a contraception law (Criminal Code, Chapter 18.

Sundquist was very critical of the Contraception Act and began writing various articles about the spread of venereal diseases,[2] as well as on improving working conditions for women and granting suffrage.

[12] Sundquist was elected to serve on the Committee of Twelve to organize the association, whose purpose was to work together internationally to advocate for women to be granted full citizenship and to create a progressive programme to promote public health.

[20] Sundquist participated in the 1922 Constitutive Assembly of the Medical Women's International Association held in Geneva and was later elected president of the organization, serving from 1934 to 1937.

[1] In 1930, along with Bascomb Johnson, an American writer, and Karol Pindór [pl], a Polish diplomat, Sundquist was appointed by the League of Nations to prepare a report on the slave trade in women and children in Asia.

[25] They began in Japan and from there travelled to China, Indochina, Indonesia and India, before moving on to Tehran, Bushehr, Baghdad, Damascus, Beirut and Haifa, and worked cooperatively with various government officials to obtain information.

[1] She is remembered as one of Sweden's most prominent pioneering venereologists in the first half of the twentieth century, actively engaged in solving social and political challenges faced by women.

[24][2] She was committed to changing laws to improve conditions for women, as well as eradicating protective legislation which treated people differently based on gender.