Impregnation is actually the fertilization process in which sperm and ovum fuse to produce a zygote.
Naturally, a human cannot impregnate a pig as there are many reproduction barriers between them.
Naturally different species cannot breed as there are many reproduction barriers most importantly there are genetic barriers. But in the laboratory, it can be produced, but human-pig chimera although still, although it is enough controversial.
So, a human can't impregnate a pig due to species barrier, genetic barrier, and reproduction barrier.