We always farrowed inside. One of the first litters we built a wooden bar across one side of a wall and hung a heat lamp over, with plenty of straw in the building, the piglets went into that spot and came out when hungry, so the sow couldn't lie on them. Needless to say none died, out of the ten she gave birth to. The last farrowing was with an experienced sow and we left her to it, she gave seven and none died, she was the best mother pig ever.