Lauren Miertschin My assumption was this, and I may be way, way off: but Esther was fitted for something, and that something was probably a diaphragm. And something went wrong with that -- possibly was not fitted correctly, or whatever else can go wrong with this device (don't know, but I do recall learning that there were some dangers with this birth control method). Right away, the doctor saw what the problem was, and he said that he could fix it. I just envisioned he was looking at a crooked or misplaced diaphragm -- however, I am really uneducated about this device, so maybe I'm way off.
Sarah She was in fact hemorrhaging. She does mention it very very briefly that that is what she thinks it is, when she shows up at joans but they never talk about it again.
Jaime I'm fairly certain she was hemorrhaging. I'm not sure why this wasn't made clear to the reader. Maybe Plath didn't think it was important to focus on the medical aspect of the bleeding, and instead wanted the reader to focus more on the symbolism-- the destruction and difficulty that came with all of Esther's romantic relationships.
Anabella I don't know much other than I assumed it was an IUD or birth control device not inserted properly and led to her hemorrhaging. The author isn't very clear what this "fitting" is supposed to be. I've never heard of it.