In 1944 she continued her studies at the University of Toronto where she wanted to get a master's degree in social work. Her professors encouraged her to pursue a career in genetics, and as a result she completed PhD in human genetics at the University of Toronto in 1951 and worked at the Hospital for Sick Children in Toronto. At the Hospital for Sick Children she studied twins and children with Down syndrome. In the 1960s she helped identify the link between pregnant women who had undergone abdominal X-rays and chromosomal birth defects such as Down syndrome in their subsequent pregnancies. She was also amongst those researchers in the 1960s who showed that the extra chromosome associated with Down Syndrome is not always from the mother, but he father may be responsible for 25 per cent of the births.