The pig will be in the first trimester. Its gestation period would be about one hundred and fourteen days. The average of pigs pregnancy is 114 days or simply you can say it is three months, three weeks, and three days the length of an adult guinea pig is twenty centimeters but mostly it will depend on size and type of the parent a guinea pig lasts seventy-five days for pregnancy. The symptoms of a pregnancy pig are the side of the belly gets bigger it takes 68-72 days before the piglets are born.