Lateral incision is not always necessary for a normal birth, but most first-time mothers choose to undergo it. Lateral incision is a type of perineotomy, where the bleeding is stopped by gauze compression after incision and sutured immediately after delivery of the placenta. The reasons for lateral incision in normal labor are as follows: 1. Some special conditions occur in primiparous women, such as tight perineum during labor, narrow vaginal opening, poor perineal elasticity, emergency delivery or perineum with edema and inflammation, etc. In order to avoid tearing the perineum and serious damage when the fetal head is delivered, so an incision is made at the left posterior side of the perineum during contraction; 2. The fetus is relatively large, the fetal head is not correct, the force of delivery is not strong, the fetal head is blocked in the perineum, also 3, if the fetus in the process of delivery has a lack of oxygen, in order to accelerate the progress of labor, you can choose to make a lateral incision; 4, the mother has high blood pressure, diabetes and other diseases, need to shorten the second stage of labor, as soon as possible to deliver the fetus, will also do a lateral perineal incision to help delivery. Of course, in addition to lateral incision, you can also choose perineal median incision during normal delivery, but the disadvantage of this surgery is the risk of natural prolongation of the incision tearing to the anal sphincter, so it is generally preferred to perineal lateral incision.