Glenn Beck says she did.
I'll revise my earlier statement: she did discuss it, but didn't advocate it.
BTW, it's a misnomer, anyway, to call the killing of a living, not-suffering, not-terminal, not-on-life-support retarded or disabled person "euthanasia". Even if the Nazis did call their T-4 Aktion program "euthanasia".
What most people mean by "euthanasia" is the passive euthanasia of people on life support like Terri Schiavo. Sanger never wrote about that. http://en.wikipedia.org/wiki/Margaret_Sanger
Sanger saw birth control as a means to prevent "dysgenic" children from being born into a disadvantaged life, and dismissed "positive eugenics" (which promoted greater fertility for the "fitter" upper classes) as impractical. Though many leaders in the negative eugenics movement were calling for active euthanasia of the "unfit," Sanger spoke out against such methods
. She believed that women with the power and knowledge of birth control were in the best position to produce "fit" children. She rejected any type of eugenics that would take control out of the hands of those actually giving birth.
Taking sharp issue in plain words with certain other eugenicists, however, Margaret Sanger completely rejected the idea of killing the unfit, expressly denouncing euthanasia as a eugenics tool
Her eugenics views are often trumpeted on many sites, but I would still maintain that calling her a "eugenicist" is mistaken. I'm not sure how much she really advocated it, versus going through the motions of it to help get wealthy WASP foundations that supported eugenics to donate money to her cause... secondly, to whatever extent she held certain eugenic views, like the above, I would say they were not her main focus. Because she spends 10% of her time discussing such matters, and 90% focusing on the rights of women, which were her main concern
. She was far more feminist than eugenicist.