She's been trying to have a baby for years. Her and her husband have been trying for so long that even the attempts are starting to lose their luster. It's hard to escape the conclusion though that whatever reason they're not having a baby is a problem at her husband's end. That's been all but confirmed with her latest visit to the fertility clinic.
So it's some strange combination of a godsend and tragic when she finally does get pregnant. Not from her husband, though. No, all those years of trying to get pregnant and when it finally does happen it's from getting raped in an alley by a stranger...
This is sort of a back-to-basics idea for me. The basic premise is a simple one - a serial rapist has become so obsessed with impregnating his victims that he is targeting women in and around fertility clinics.
Needless to say, hijinks ensue. Looking for victims of his mad urge to breed women willing to have children, then possibly getting pregnant in the last way they expected. If more then one is interested in this we can work out something still.