Gianna was born in 1922 in Magenta, Italy as Gianna Francesca Berretta. She was born into a family of 13 children as the 10th one. Only nine of the children in her family survived into adulthood.

She began studying medicine in Milan in 1942 and received a medical diploma in 1949 where she opened an office specializing in pediatrics close to her home of Magenta.

Gianna had hopes of working with her missionary priest brother in Brazil, though her chronic poor health made this impossible, so she remained practicing in Italy. She married and had two children and then suffered two miscarriages. When she became pregnant again, she developed a uterine tumor. She opted to have it removed, without terminating the pregnancy. Her baby was born healthy but Gianna died of complications a week later.

St. Gianna is the patron saint of preborn children, mothers, and physicians. Her feast day is April 28 and she was beatified by Pope John Paul II.