How long after sows start contractions do they start delivering the pigs?

There are three phases to parturition. The first is the preparatory phase which can last 2-12 hours. During this period the cervix and pelvic canal softens and dilates. At the end of stage 1, complete dilation is achieved. Stage 2 begins with the expulsion of the fetus and can last 1-4 hours. Stage 3 is the expulsion of the afterbirth and this takes 1-4 hours also. Contractions actually begin as very low strength and low frequency uterine contractions. These may only cause the sow to show some slight discomfort or restlessness. As the contractions become more frequent and more intense, the sow will show even more behavioral changes, such as frequently getting up and down. When the contractions have been hard enough and frequent and the cervix has dilated enough, a piglet will just enter the pelvic canal. This then initiates a reflex in the sow to begin pushing. This is visible by watching the sow contract her abdominal muscles. This is when the sow enters phase 2. Piglets should typically come at 15-30 minute intervals once the sow begins delivering. But, the first piglet may take some time to come as dilation must be completed.