During her stay in London, she was also associated with Women’s Indian Association and the Women’s Freedom League.  In 1938 Avabai represented All India Women’s Council in Geneva. 

Avabai moved to Bombay permanently in 1941. She became an active member of All India Women’s Conference after joining it in1944 when Kamaladevi Chattopadhyay was the President of AIWC. She developed interest in Reproductive Health and Family Planning which later became her life-long mission. With the initiative of Shrimati Dhanwanthi Rama Rao, and others Avabai Wadia, established the Family Planning Association of India on 23rd July, 1949 at Bombay.

Shrimati Dhanwanthi Rama Rao was the founder President and Avabai Wadia was the Honorary General Secretary of the Association. Avabai Wadia. She  was elected as President in 1964 on which post she continued for 34 years. She had strong ethical and moral concerns and was convinced about the role of family planning in improving the lives of women and establishing gender equality.  She thought that Family Planning was a means of helping women to get out of the trap of biological compulsions and social pressures for frequent child bearing, which leads to deterioration of the health, neglect of children and financial problems in the family. Avabai strongly believed that family planning could be successful only if it was voluntary and done through informed choice.

During her leadership, Avabai expanded her work all over India to more than 15 States. She initiated branches all over the country to reach the maximum number of people.  

Between 1963 to 1980, Avabai started family planning services for industrial workers, and low income communities in cities like Mumbai, Thane, Kanpur, and also in rural areas.  These services were broadened by adding programmes on sex education, population education, and women’s empowerment. From November 1952, she guided the work of the International Planned Parenthood Federation (IPPF) initiated in Bombay, establishing World Wide Regional Offices. She founded autonomous family planning associations, under the umbrella of the federation and raising funds for its work.  

She was the President of IPPF from 1983 for two terms when IPPF was awarded U N Population Award in 1985 and Third World Prize in 1987.  During Avabai Wadia’s term as a President of IPPF, the Federation could not avail of American aid of 17 million dollars due to the disagreement of IPPF with the American stance on abortions.

Avabai Wadia was a world trotter. She travelled across the globe, addressing many public meetings and seminars and her speeches were well appreciated by the learned audience. She was conferred an Honorary Doctorate in May 2005 by the International Institute of Population studies for her contribution to the field.

Avabai Wadia was an intelligent, sensitive and energetic person with very a strong memory and affection for human beings. She used to surprise people by recognizing them with their first names even after many years and also recalling details about their previous meetings. Avabai, throughout her life, continued to campaign and advocate human rights and greater understanding of the concept of ‘Vasudhaive Kutumbakam’ (the world is one family) among people and spread the message of unity and equality.

Avabai was a prolific writer and orator. She became the editor of the Journal of Family Welfare from June, 1956 and continued till April, 1999. In 1993 the Journal received the Golden Media Award of the Population Institute, USA. Her autobiography, The Light is Ours: Memoirs and Movements, is a detailed and fascinating personal account of one of the great revolutions after the Second World War. Avabai Wadia wrote a column for 5 years in Blitz, a weekly published in Bombay.  

Family Planning Movement in India summed up her life mission thus "I found that my own life has been so intertwined with my work with people and organizations that I find it impossible to detach the two.”

Avabai Wadia breathed her last on 11th July, 2005, World Population Day, a fitting day.