What signs appear before a sow is about to give birth?

Two weeks before a sow gives birth, the udder gradually swells. From 2 to 3 days before farrowing, squeezing the front teats shows a small amount of milk. If the milk comes out in a spray, birth will occur in no more than one day. If the last pair of teats can also be squeezed to release a large amount of milk, birth will occur in about 6 hours. From 6 to 12 hours before farrowing, the sow often carries straw in her mouth to make a nest; when there is no straw, she will also root at the ground with her snout and paw at the ground with her front hooves as if making a nest. If she is restless, standing and lying down uneasily, sometimes sitting like a dog, curling her tail, urinating frequently, and discharging thin blood-tinged mucus from the vulva, commonly known as "water breaking," it indicates that she is about to farrow. Preparations for assisting the birth should be made.