"An ad that uses sports to divide rather than to unite has no place in the biggest national sports event of the year - an event designed to bring Americans together," said Jehmu Greene, president of the New York-based Women's Media Center.
The center was coordinating the protest with backing from the National Organization for Women, the Feminist Majority and other groups.
CBS said it has approved the script for the 30-second ad and has given no indication that the protest would have an impact. A network spokesman, Dana McClintock, said CBS would ensure that any issue-oriented ad was "appropriate for air."
The ad - paid for by the conservative Christian group Focus on the Family - is expected to recount the story of Pam Tebow's pregnancy in 1987 with a theme of "Celebrate Family, Celebrate Life." After getting sick during a mission trip to the Philippines, she ignored a recommendation by doctors to abort her fifth child and gave birth to Tim, who went on to win the 2007 Heisman Trophy while helping his Florida team to two BCS championships.