The main mechanism of contractions is to make the uterus contract, so that the exposed capillaries and small blood vessels can be contracted accordingly, so that the uterine bleeding can be reduced and gradually stopped, so the contractions are a protective mechanism. After the contraction, the woman will experience pain in the lower abdomen, which is generally tolerable and therefore does not require special pain management. After the contractions last for a certain period of time, the contractions will disappear as the vaginal bleeding gradually decreases.