While you don't really get pregnant FROM anal sex, you can get pregnant from the semen dripping into the vagina, as duke and Casper have pointed out... so by the same token, you could get pregnant from sitting in the wet spot.

__________________
Put me on wheels and I'll turn tricks.

Clever? Nah, I ran out of that years ago. But if you find this, let me know, k?
"The road goes ever on..." ~ Tolkien

In memory of my friend skip...
Go then, there are other worlds than these