I suggest a thesis that focuses on the oppression and destruction of the female characters that originates in the male characters' faulty perceptions of the female characters physical, mental, and/or social make up. You may also consider tying in the irony in both of these stories.
Maybe something like:
The oppression and destruction of the protagonists in "Desiree's Baby" and "The Yellow Wallpaper" originate in the male characters' inaccurate perceptions of the protagonists. The men in these stories eventually ruin the protagonists based on faulty assumptions related to the protagonists' physical, mental, and/or social stature.
Or, to tie in the irony:
It is ironic that the protagonists who are oppressed and destroyed in two short stories, "Desiree's Baby" and "The Yellow Wallpaper", are really not the ones who are flawed or otherwise abnormal.