Question about Sylvia Plath's The Bell Jar.?

I am extremely fond of Sylvia Plath's works, but one thing has always plagued me about The Bell Jar. Why does the character Esther Greenwood bleed so profusely after having with Irwin. I understand that she was a virgin, but when she went to the hospital the doctor said that she was "one in a million" and that he could fix her problem. What happened? I truly hope that I am not the only person who has wondered this same thing. Thanks to all who can help.