Female pig had stillborn piglets

Question
I live on a farm and about 7 months ago rescued a female pig from a lady who had bred her in a residential home. I took the mother and piglets, and was able to find homes for all of the babies. I kept the mother and she has been living with me. This morning I awoke to find that she had given birth to stillborn piglets on my floor. I have no idea how this could be possible, because she is the only pig I have, and she has had no contact with any male pigs for the past 6 months.  I searched online and could find nothing about this. They are not mummified, and their coloring looks normal. The mama is acting normal and has been eating well the whole time as well. Do you know how this could have happened?

Answer
The gestation period for pot-bellied pigs is three months, three weeks and three days. If this sow has really, truly not been near any boar for the past six months -- then I am at a total loss.

Pigs can and do mate through wire fencing. If you live in an area where wild pigs are present, then your sow may have been exposed to a boar without your knowledge. It's also possible that an intact pet boar escaped from a neighbor and mated with your sow through a fence, that has happened before.

The only way to know for sure why they were stillborn is to have a veterinarian do a necropsy on one of the stillborns. The three most common natural causes for spontaneous abortion or stillbirth are severe congenital defects, trauma (dog attack or a hard kick to the stomach) and malnutrition.

I highly recommend having your sow spayed. Spayed pigs make better pets, they don't go into heat and there's no risk of pregnancy or uterine tumors. There's a list of vets that see pot-bellied pigs here www.farec.org   Sheperds Green Sanctuary http://www.9sites.org/ has a Helping Hoof fund that helps spay and neuter rescued pigs.