Pigs are pregnant for about 114 days, which is a little less than four months. A pregnant pig, often referred to as a piggy sow, sometimes delivers a couple of days early or late.
Farmers often use ultrasound to determine if a pig is pregnant because a pregnancy is not physically obvious until near the end of the term. A sow has a litter of at least four piglets each time she delivers. If she does not have at least four embryos during gestation, her body causes the pregnancy to end spontaneously. The sow nurses her piglets for up to six weeks before they are weaned.