According to George Marlin, she was:
Yet despite her harangues against the Church and her insistence that “for the welfare of children, for the happiness of husbands and wives, and for the full realization of Women’s rights, birth control by scientific methods of contraception [should] properly and wisely be exercised,” she did make one exception to an otherwise thorough pro-choice agenda: abortion.
That’s right. Margaret Sanger actually stated that: “Birth control does not mean abortion.” Here are her exact words:
“The real alternative to birth control is abortion,” wrote Dean Inge, [Dean of St. Paul’s Cathedral, London]. It is an alternative that I cannot too strongly condemn. Although abortion may be resorted to in order to save the life of the mother, the practice of it merely for limitation of offspring is dangerous and vicious. [Emphasis added] I bring up the subject here only because some ill-informed persons have the notion that when we speak of birth control we include abortion as a method. We certainly do not. Abortion destroys the already fertilized ovum or the embryo; contraception, as I have carefully explained, prevents the fertilizing of the ovum by keeping the male cells away. Thus it prevents the beginning of life. [Source: Margaret Sanger, "Birth Control Advances: A Reply to the Pope," 1931, Margaret Sanger Papers, Sophia Smith Collection, Smith College MSM S71-243.]
I bet you never heard that Sanger considered abortion “dangerous and vicious.” You can take it to the bank that there are no posters hanging on the walls of Planned Parenthood clinics quoting those particular words of the founder.