If you take a look at page 102 of the April, 1933 issue of the Birth Control Review (Sanger's Journal of her Birth Control League which, after the war, morphed into Planned Butcherhood) you will note an interesting article titled, Eugenic Sterilization: An Urgent Need. The doctor was Dr. Ernst Rüdin. In case you're not familar, Dr. Ernst Rüdin was honored by Hitler as being the "pioneer of the racial-hygienic measures of the Third Reich." He was one of the collaborators of Margaret Sanger.
Sanger was a child of the sexual revolution 50 years before the sexual revolution was even conceived. She believed the birth of a child was a shame and a large family was a catastrophe:
Many, perhaps, will think it idle to go farther in demonstrating the immorality of large families, but since there is still an abundance of proof at hand, it may be offered for the sake of those who find difficulty in adjusting old-fashioned ideas to the facts. The most merciful thing that the large family does to one of its infant members is to kill it.
Margaret Sanger, Woman and the New Race, (New York: Eugenics Press, 1920), chapter 5.
(btw, if you click on the link, there's even worse to read in that book)
Here's another one from her 1926 "epic" Pivot of Civilization (available on the Web Archive:
And then there's this, from the February, 1919, edition of the Birth Control Review (available here):
What a quote: …seeking to assist the race toward the elimination of the unfit.