Write down the exact date you begin mating your sow. The first three weeks of mating is the most likely time she will conceive. This is because a sow's estrus cycle lasts for this amount of time. Look for signs of pregnancy once mating is complete. Your sow may become easily irritated, the vulva will be red and swollen or the sow may start nesting by gathering straw for a bed to give birth.
Check your sow's progress weekly and record your findings. Date each examination to help you keep track of her pregnancy and the fetus' potential age.
Check your sow's pregnancy through ultrasound. Ultrasound machines are available to farmers and veterinarians for use on pregnant livestock. Measure the fetus from snout to anus using the ultrasound machine controls. Measurements will lend to the gestational age. For example, a fetus that is 40 cm. is approximately 56 gestation days old.
Watch your sow for signs of impending delivery. Signs can begin two to three weeks before actual delivery takes place. Your sow may take birthing positions such as lying down with legs outstretched, heavy, rapid breathing and restlessness which increases as labor nears.