Speaking at the Cathedral of Our Dear Lady, which is the Munich Catholic Archbishop's own cathedral and one of the most important Catholic churches in Germany, Käßmann warned against demonising birth control.
Contraception, including the pill, is forbidden under the Catholic Church's strict moral code.
“We can however also see it as God's gift, for it is about the preservation of life, of freedom, which doesn't have to immediately degenerate into pornography, as much as the sexualisation of our society is, of course, a problem.
“It's about love without fear and about responsible parenthood. And for women, in fact, it's about concern for their own lives and those of their own children.”
It was also about the decision not to have children, “which our Churches should not always devalue,” she added.
Käßmann was speaking as part of the 2nd Ecumenical Church Congress, which is Europe's biggest interfaith gathering. Hundreds of thousands of believers of all denominations are in Munich to put aside theological differences and find common ground.
Käßmann, herself a mother of four children, stepped down as leader of Germany's Protestants in February after she was caught driving drunk.
The strict sexual code of the Catholic Church has been the subject of robust debate lately, owing to the child sexual abuse scandal that has rocked the Church. Earlier this week, Alois Glück, president of the Central Committee of German Catholics, which is the Church's largest lay organisation, called for a complete review.
“We must openly grapple with, for example, the question that some 90 percent of Catholics deal with birth control other than the Church instructs,” he told daily Frankfurter Rundschau.
A recent poll found a massive 81 percent of Catholic thought celibacy for priests should be abolished.
In her speech, Käßmann went on to highlight the mortality rate for mothers and infants. Each year more than 300,000 women die as a result of pregnancy or childbirth, 99 percent of them in poor countries, she said.