Apparently if, after a day of starving* yourself right as you’re ovulating, you give your boyfriend oral sex and then almost immediately get stabbed in the abdomen in such a way that the contents of your stomach merge with your uterus before the stomach acid has a chance to kill the sperm … there may be a small chance that you might get pregnant**.
I don’t think that it’s something you should worry about. You’re a lot more likely to get an STD from oral sex than get pregnant from a knife wound.
The Take Home Message: Avoid getting stabbed in the belly… and don’t swallow.
*People who starve themselves may have less acid in their stomachs. Sperm don’t like acid. Even the normal mild acidity of the vagina would kill them if it weren’t for the buffering capacity of semen.
**Based on the transcription of a 1988 case report from the British Journal of Obstetrics and Gynecology. I’m trying to get a copy of the paper and the follow-up article, because the sheer number of things that had to go wrong for this to happen are almost unbelievable.