chemotherapy can result in temporary or permanent infertility. There would be no point in impregnating her while she was going through chemo because it would kill the baby, but afterward, if she wanted to become pregnant and she was told she was permanently infertile (especially if the cancer was of the ovaries), then it would make sense. It could be that she doesn't have cancer at all and that her physical appearance was due to whatever juliet was putting in her body to try and fix her infertility. Or maybe she has already gone through menopause. I'm sure there are a million more possibilities.