Adopted female living with a male

I just picked up 3 pigs needing a home because the couple is moving and could not take the pigs. They had an add on Craigslist to sell them and did not. As it turns out...it was a male and 2 females. Would love some guidance to figure out if either of the females are pregnant, the owner said that one had a litter about 3 months ago. All three pigs were living together in pet store cage! I build a temporary C&C for the females today, I have found a new home for the girls, but I would like to observe and be sure they are not pregnant. Does anyone have and advice on signs?