Postpartum hemorrhage is called postpartum hemorrhage when the amount of blood in the vagina is ≥500ml within 24 hours after delivery of the fetus; massive uterine bleeding that occurs during the puerperium after 24 hours of delivery is called late postpartum hemorrhage. Postpartum hemorrhage is one of the serious complications during labor and delivery, and still ranks first in maternal mortality in China. Once it occurs, the prognosis is dangerous, and those in severe and prolonged shock may still develop secondary hypopituitarism – Sheehan syndrome – even if they are rescued. When conservative treatment fails to endanger maternal life, internal iliac artery ligation or hysterectomy is usually used as the final means of hemostasis. With the popularization of interventional radiology in clinical practice, it has been successfully applied to the treatment of postpartum hemorrhage since 1979, and now has achieved recognized results as the method of choice for refractory postpartum hemorrhage. Vascular interventional therapy has shown obvious advantages in the treatment of postpartum hemorrhage, with the characteristics of minimally invasive, precise hemostatic effect and preservation of uterine and reproductive functions, especially for patients with coagulation dysfunction in obstetric hemorrhagic shock, providing a new and safer method of resuscitation. I. Indications and contraindications (a) Indications 1. various refractory postpartum hemorrhages that have been invalidated by conservative treatment; 2. postpartum hemorrhages of up to 1000 ml that still have bleeding tendency after active conservative treatment; 3. various refractory late postpartum hemorrhages that have been invalidated by conservative treatment. (2) Contraindications 1. Patients with DIC who have bleeding from other organs; 2. Patients whose vital signs are extremely unstable and cannot be easily moved. The choice of surgical modality and treatment mechanism (a) The choice of surgical modality There are two types of vascular interventions for postpartum hemorrhage, one is percutaneous double internal iliac artery embolization (IIAE) and the other is percutaneous double uterine artery embolization (UAE), both of which belong to the category of transcatheter arterial embolization (TAE). At present, patients who choose interventional treatment in China are critically ill, therefore, IIAE is preferred; for some patients with postpartum hemorrhage in good general condition, or those who are quite skilled in intubation by the operator, UAE can be chosen to reduce the occurrence of complications. Because of the obvious unilateral nature of uterine blood supply, that is, under normal conditions, one uterine artery supplies the ipsilateral uterine body, and although there are abundant traffic branches in the middle of the uterine body, most of them are normally closed, and only when the contralateral uterine artery is unable to supply blood does the traffic branch open to supply the contralateral uterine body, so embolization of only one uterine artery or the anterior trunk of the internal iliac artery will lead to treatment failure. (2) Treatment mechanism IIAE or UAE selectively embolizes the bleeding artery, the embolic agent not only occludes the bleeding artery, but also causes a significant decrease in arterial pressure in the bleeding organ – uterus, which slows down the blood flow and facilitates thrombus formation; at the same time, due to the reduction of uterine blood supply, the contraction of uterine smooth muscle fibers is strengthened due to ischemia and hypoxia, which controls the bleeding from the other side. DSA images vary in different types of postpartum hemorrhage cases, but in general, they show signs of hemorrhage. DSA imaging shows diffuse or focal contrast spillage in the uterine cavity, thickening and distortion of the superior branches of the uterine arteries bilaterally, and no obvious signs of vascular rupture. 2.Placental implantation postpartum hemorrhage DSA imaging shows significant thickening and outward displacement of the uterine arteries bilaterally, and intrauterine equivalent to placental implantation out of the uterus is seen as focal contrast dye thickening and overflow. 3.Postpartum hemorrhage caused by incisional dehiscence after cesarean section Most commonly seen in lower uterine segment transverse incisional cesarean section, often due to vascular injury on both sides of the incision or incision too low secondary to infection and poor healing of the incision.DSA imaging shows blood in the superior or inferior branch of uterine artery on one side, and at the incision of lower uterine segment, obvious contrast agent spillage is seen, and there is still contrast agent retention in the venous phase. In general, typical bleeding with contrast spillage and pooling is seen in the arterial phase, and the spillage is more pronounced during serial imaging. At the end of the contrast phase when the intravascular contrast is completely washed away by the blood flow, the contrast spillage is more clear. The more frequent bleeding is a continuous small amount of blood spillage. The application of digital subtraction technique can more clearly detect small vessel bleeding and the site of bleeding, but intestinal artifacts often interfere with the quality of DSA images. The radiographic signs of contrast spillage depend on the rate of bleeding and the collection of exudate in the tissue spaces. In very active continuous bleeding, a wide range of contrast aggregation is easily seen. A small amount of contrast spillage often appears as irregular focal aggregation, and signs of contrast spillage from the vessels can be seen when the bleeding rate reaches 0.5 ml/h. If there is a clot around the bleeding site, then as bleeding continues a duct may be flushed out between adjacent clots. The extravasated contrast agent flows into it and produces a tubular shadow that resembles a vein. This tubular shadow is slow to disappear, unlike the signs that disappear quickly after venous angiography. In patients with postpartum hemorrhage, it is worth paying special attention to the fact that due to the enlargement of the pregnant uterus, the course of the uterine artery also changes, from the original internal iliac artery, which first travels downward along the pelvic wall and then inward, to first travel downward along the pelvic wall, then outward and then upward. The choice of embolic agent for postpartum hemorrhage should pay attention to two issues in the choice of embolic agent: firstly, stopping hemorrhage as soon as possible is the primary problem in patients with postpartum hemorrhage, and the preference of IIAE in the procedure determines that the choice of intraoperative embolic agent is mainly medium-effect; secondly, the characteristics of pelvic blood supply should be noted in the choice of embolic agent. The internal iliac artery is divided into uterine artery to supply the uterus, and there are also upper and lower bladder arteries and inferior rectal artery to supply blood to the bladder and rectum respectively, so the above problems should be taken into account when choosing embolic agents. Fresh gelatin sponge granules are absorbable medium-acting embolic agents, which can be absorbed by blood vessels and reopen the blood in 2-3 weeks after embolization. And it can only embolize to the peripheral arteries, not the precapillary arteries and capillary beds, which ensures the smooth circulation of the small capillary arteries, so that the uterus, bladder, rectum and other pelvic organs can get enough nutritional blood supply and no pelvic organ necrosis can occur. Certain very fine materials such as gelatin sponge powder and liquid materials such as anhydrous alcohol, which can destroy capillary beds, are extremely effective for embolization of renal tumors, but are inappropriate or contraindicated for hemostatic embolization of postpartum hemorrhage, which can cause ischemic necrosis of pelvic organs. Fresh gelatin sponge granules are dissolved into a paste with contrast and antibiotics to embolize the internal iliac artery via catheter, and the contrast can clearly observe the site of vascular embolization to prevent misembolization or regurgitation. For patients with postpartum hemorrhage in good general condition, UAE is also an option for the procedure. Due to the super-selective access to the uterine artery, there are relatively few complications and the choice of embolic agents is more lenient. Both medium-acting embolic agents – gelatin sponge particles and some permanent embolic agents with larger particles such as PVA, KMG, real silk wire segments, etc. can be chosen, but it is still recommended that medium-acting embolic agents are safer. Fifth, the choice of drugs in patients with postpartum hemorrhage, due to the large amount of bleeding, while the patient is postpartum weakness, low body resistance, very easy to lead to pathogenic invasion, so intraoperative in the arterial cannula in place after the push injection of broad-spectrum antibiotics is necessary. A certain amount of antibiotics should also be added to the embolic agent in order to have a high concentration of potent antibiotics acting on the local tissues for a longer period of time. VI. Clinical efficacy and evaluation Traditionally, for refractory postpartum hemorrhage that has failed to respond to conservative treatment, two surgical procedures are often used. One is bilateral internal iliac artery ligation, which is technically difficult and has a low success rate, with an efficiency of 42% as reported in the literature. After internal iliac artery ligation, the terminal arterial pressure at the distal end of the ligated internal iliac artery decreases by up to 84%, the mean arterial pressure decreases by 24%, and the blood flow decreases by 48%. Since the distal lumen of the internal iliac artery is not occluded, blood flow can enter the unoccluded lumen of the internal iliac artery through the remaining larger traffic branches to the uterine artery, and rebleeding occurs. The other is subtotal or total hysterectomy, with significantly increased surgical risk and the fact that most patients with postpartum hemorrhage are young women and hysterectomy means permanent loss of the uterus. Removal of the uterus will inevitably affect the endocrine function of the ovaries, which affects the physical and mental health of the woman, since 50-70% of the ovarian blood supply comes from the ovarian branch of the uterine artery. Vascular intervention can be performed by introducing a catheter into the bleeding artery through the femoral artery puncture to avoid opening the abdomen, and using gelatin sponge pellets to embolize the trunk of the bleeding artery starting from the end, thus effectively controlling the bleeding. The gelatin sponge only embolizes the terminal artery, not the precapillary artery and capillary bed, and a small portion of the blood supply can be obtained through other traffic branches without tissue necrosis. The vascular interventional technique is relatively simple, with short operative time, rapid and complete hemostasis, high success rate, no recurrence, and preservation of the uterus, making it a new and effective alternative to hysterectomy in the treatment of refractory postpartum hemorrhage, easily accepted by patients of childbearing age, and of great clinical significance in the treatment of postpartum hemorrhage. For postpartum hemorrhage caused by implanted placenta and incomplete placental abruption, vascular intervention can not only stop the hemorrhage quickly, but also the implanted or residual placenta can be delivered naturally through the vagina due to ischemic necrosis, which avoids hysterectomy or further removal of the placenta, fully reflecting the advantages of vascular interventional technology in the treatment of refractory postpartum hemorrhage. The effect of vascular interventional treatment for postpartum hemorrhage has been called “dramatic effect” and has become the first choice of treatment in hospitals with conditions. Seven, complications and their prevention and treatment of postpartum hemorrhage vascular interventions are not many complications, the following are common in clinical practice: 1, pain pelvic, lumbosacral, perineal, anal, buttock pain, generally tolerable, 3-11 days natural relief, no special treatment, but also can take anti-inflammatory pain drugs symptomatic treatment. If available, PCA analgesia can be done for patients on the day of surgery and the day after surgery. 2.Low fever Mostly below 38℃, lasting 4-9 days and disappearing without special treatment, and can also be treated symptomatically with anti-inflammatory drugs. 3.Lower limb pain, weakness and numbness are relatively mild and will be relieved within two weeks, no special treatment is needed. 4.Other complications such as arterial intima injury, arterial spasm, ectopic embolism, etc., as long as the operation is standardized, skilled and gentle, generally rarely occur. VIII. Prospects of application and outlook Vascular interventional techniques for refractory postpartum hemorrhage are undoubtedly the best treatment means at present, and this method should be recommended in hospitals with conditions. However, it is undeniable that since the history of this technology for the treatment of postpartum hemorrhage is not long, it has not been widely accepted and applied in the field of obstetrics, and there are still many issues that need to be explored and studied, such as: the exact indications and contraindications of vascular intervention for postpartum hemorrhage, how many milliliters of postpartum hemorrhage should be treated with vascular intervention, the timing of vascular intervention, the selection of embolic agents and new types of embolic agents, the screening of embolic agents, and the treatment of postpartum hemorrhage. embolic agents, improvement of embolization techniques, the time of endometrial repair and the effect on ovarian function, etc. The vast majority of scholars believe that when the amount of postpartum bleeding reaches 1000 ml, when late postpartum bleeding reaches 500 ml at one time after conservative treatment is ineffective and there is a tendency to continue bleeding, when the effect of using contraction agents is not good, and when placental residue or soft birth canal laceration is excluded, vascular interventional treatment should be considered promptly to stop bleeding.