Cesarean section uterine incision scar pregnancy has been on the rise in the last decade or so. If not diagnosed early or handled appropriately, severe bleeding and uterine rupture may occur, resulting in the removal of the uterus in order to save the patient’s life and the loss of the patient’s ability to bear children, which causes incalculable damage to the woman’s health. I. Definition and risk The pregnancy in which the egg is deposited in the uterine scar of cesarean section is called cesarean section uterine incision keloid pregnancy, and it is an extremely rare and specialized form of ectopic pregnancy. If the gestational sac grows into the uterine cavity, the pregnancy may continue, but complications such as uterine rupture and severe bleeding often occur in the middle and late stages; if the chorionic villi are deeply implanted in the scar, bleeding or even uterine rupture occurs in the early stages of pregnancy, which is extremely dangerous. Clinicopathologic types of CSP (1) Early cessation of embryonic development (1) Localized absorption of the gestational sac: the endometrium at the scar is underdeveloped due to cesarean section injury, and the pregnant egg is planted at the scar, so the embryo will stop developing early due to malnutrition. When the gestational sac is small, it can degenerate and absorb on its own without causing obvious clinical symptoms, or only a small amount of vaginal bleeding; (2) detachment of the chorionic villi of the gestational sac: (1) uterine bleeding: when the gestational sac is large and not easy to be absorbed, the chorionic villi can cause uterine bleeding because the muscle layer at the place of implantation is thin and scarred, and the contraction of the muscle wall is poor, and it is not easy for the broken blood vessels to be closed. Bleeding dribbling or continuous, sometimes more or less, or sudden heavy bleeding, or even rapid as a spring, resulting in a drop in blood pressure, shock; ② bleeding localized pooling: bleeding and stopping the development of the gestational sacs mixed with the formation of clots, clots with the increase in bleeding and growth, ultimately leading to uterine rupture, intra-abdominal hemorrhage; ③ bleeding into the uterine cavity: bleeding to the uterine cavity to expand the uterine cavity can lead to accumulation of blood in the uterine cavity, easy to misdiagnose as abortions, difficult to avoid the miscarriage of the uterine cavity, incomplete abortion and grapes and other anomalies. Bleeding into the cervical canal: the bleeding does not flow out in time, but accumulates in the cervical canal, and the cervix is enlarged, which can be misdiagnosed as cervical pregnancy, difficult to avoid miscarriage and other anomalies. 2. Continued development of the embryo (1) Early rupture of the uterus: the pregnant egg settles and develops deep in the keloidal fissure and the cystic cavity dilates and breaks through the thin myometrium, or even the plasma membrane layer, resulting in rupture of the uterus and intra-abdominal hemorrhage. 2. If the gestational sac grows towards the isthmus and the uterine cavity and continues to develop, sooner or later placenta previa, placenta implantation and a series of related complications in the middle and late stages of pregnancy and delivery, such as late miscarriage, preterm labor, uterine rupture, and hemorrhage of the placenta that does not detach or detachment surface after delivery, will occur. The clinical manifestations of cesarean section uterine incision scar pregnancy vary according to the location of the fertilized egg, the depth of implantation, the presence or absence of bleeding, the length of bleeding time and the amount of bleeding. Symptoms (1) Normal early pregnancy reaction: no difference from normal intrauterine pregnancy; (2) Vaginal bleeding: the patient may not have any abnormal bleeding at the time of consultation. If there is bleeding, it is often the main symptom of the consultation, which can be manifested in the following different forms: ① natural situation: vaginal bleeding or continuous, bleeding is not much or like menstruation, or suddenly increased, or manifested as a sudden large amount of bleeding, with large blood clots, blood pressure drops, and even shock; ② after abortion: manifested as a large amount of bleeding during the operation, gushing or even difficult to control, and a drop in blood pressure or even shock in a short period of time. After abortion surgery: the bleeding is heavy, gushing or even uncontrollable during the surgery, with a short period of time. It can also be manifested as continuous bleeding or sudden increase in bleeding after operation; ③ After medication abortion: there is often no obvious tissue discharge or only a small amount of membrane-like tissue discharge after medication. After medication abortion: there is usually no obvious tissue discharge or only a small amount of membrane-like tissue discharge after using medication. After medication abortion, the vaginal bleeding persists or increases suddenly, and hemorrhage occurs during the purging operation; (3) Accompanying Symptoms: most of the time, the abdominal pain is slight or absent. If there is a lot of bleeding for a short period of time, symptoms of blood loss and shock may appear; 2. Signs Most of them do not have special signs, but when hemorrhage or uterine rupture occurs, corresponding signs will appear; 2. Continued development of the embryo (1) Early rupture of the uterus: the pregnant egg will be deposited and develop deep in the scar fissure, and the cystic cavity will dilate and break through the thin myometrium and even the plasma membrane layer, resulting in rupture of the uterus and intra-abdominal hemorrhage; 2. (2) Middle and late hemorrhage: if the gestational sac grows towards the isthmus and the uterine cavity and continues to develop, sooner or later placenta previa, placenta implantation and a series of related complications in the middle and late stages of pregnancy and delivery, such as late miscarriage, preterm labor, uterine rupture, and hemorrhage of the placenta that does not detach or detachment surface after delivery, will occur. （Ultrasound is a reliable and simple means to determine the diagnosis of CSP. Transvaginal ultrasound is more conducive to observing the position of the gestational sac in relation to the uterine cesarean section incision scar; transabdominal ultrasound is conducive to understanding the relationship between the gestational sac or mass and the bladder, and to measuring the thickness of the local muscular layer; a combined examination of the two types of ultrasound can provide a more comprehensive understanding of the condition. The characteristics of ultrasonography are as follows: (1) no gestational sac is seen in the uterine cavity and cervical canal, and the endometrial line is visible; (2) the gestational sac or inhomogeneous mass is seen in the anterior wall of the uterine isthmus; (3) the continuity of the muscle layer at the scar is interrupted, the muscle layer becomes thin, and the interval between the bladder and the bladder is narrowed; (4) the color doppler flow imaging (CDFI) shows that there is blood in the surrounding of the gestational sac or inhomogeneous mass; and (5) the bladder is not in the vicinity of the uterus. (4) Color Doppler Flow Imaging (CDFI) shows blood flow around the gestational sac or inhomogeneous mass, and the flow rate is increased; (5) Blood HCG test Blood HCG value does not differ from normal pregnancy, or is lower than normal due to embryonic abortion. Clinically, blood HCG measurement is mainly used to monitor the therapeutic effect; 3. Other examinations: three-dimensional ultrasound, MRI and laparoscopy are generally not used as routine examinations, and are only applied to special and difficult cases when diagnosis is difficult. （Differential diagnosis 1. Isthmus pregnancy refers to all pregnancies in which the pregnancy egg is deposited in the isthmus of the uterus, including the lateral or posterior wall, and therefore there is no history of cesarean section. The gestational sac grows toward the uterine cavity, the continuity of the isthmus muscle layer is mostly uninterrupted, and the uterine morphology is normal; 2. Cervical pregnancy: Clinical manifestations are similar to those of CSP, and it is easy to be confused, and it mainly relies on ultrasound to differentiate it. In cervical pregnancy, the cervix is uniformly enlarged so that the whole uterus is in the shape of a gourd with a small upper part and a large lower part, and the lesion is confined to the cervix without exceeding the internal osseous region, which is closed and the isthmus is not enlarged. The cervix is closed and there is no enlargement of the isthmus. A gestational sac-like echo can be seen in the cervical canal, with fewer embryonic buds and fetal centers, and the embryo mostly stops developing. In the presence of hemorrhage, there may be a heterogeneous medium or low echogenic mass. The endometrial line is clear without a gestational sac. The myometrium of the uterine isthmus is continuous and structurally normal; 3. Difficult abortion of intrauterine pregnancy Difficult abortion is often accompanied by vaginal bleeding with paroxysmal abdominal pain, which is gradually aggravated, and seldom has serious and massive bleeding. ultrasound imaging helps to identify the pregnancy sac, which is usually in the uterine cavity, but can also be moved to the lower part of the uterine cavity or even to the cervical canal, but it is connected with the tissue in the uterine cavity. The uterine cavity may be blood-soaked, the endocervical os is usually open, but the isthmus is not significantly enlarged, and the anterior wall of the uterine isthmus is continuous with the myometrium. After the gestational sac is discharged, bleeding decreases significantly, abdominal pain disappears, and the uterus soon returns to its normal shape on ultrasound follow-up; 4. Incomplete abortion of intrauterine pregnancy: vaginal bleeding is accompanied by tissue discharge, and thereafter bleeding persists, with slight abdominal pain; ultrasound visualization of an incomplete abortion shows the uterus to be smaller than the number of weeks of menopause, with heterogeneous echoes in the uterine cavity, which may be accompanied by cystic areas, with a non-expanded isthmus, and a continuous muscular layer of the isthmus of the anterior wall; 5. CSP with bleeding stasis in the uterine cavity. CSP may be confused with hyperemesis gravidarum when there is intrauterine hemorrhage. The uterus may be significantly enlarged and soft in hyperemesis gravidarum, and the uterine cavity is often honeycombed or snowy and heterogeneous on ultrasound, while partial hyperemesis gravidarum is characterized by a gestational sac-like structure without isthmus dilatation and enlargement, and the myometrium of the anterior wall of the uterine isthmus is continuous. In cases of CSP with embryonic abruption, uterine bleeding, and no visible gestational sac, the diagnosis of choriocarcinoma infiltrating the myometrium is likely to be misdiagnosed. Choriocarcinoma is prone to distant metastasis, and blood HCG levels are usually high and tend to increase. If necessary, regular follow-up of ultrasound and blood HCG measurement, combined with medical history and tissues discharged from examination, will assist in the diagnosis. The principle of treatment is to remove the lesions and ensure the safety of patients. According to the patient’s age, condition, ultrasound image, blood HCG level and fertility requirements, the following treatment plan is provided. Before treatment, patients must be fully communicated with and sign an informed consent form. 1. Anticipation is mainly applicable to patients who are in good general condition, asymptomatic, the gestational sac is growing towards the uterine cavity, and the patient strongly wants to continue the pregnancy. However, because of the risk of miscarriage, preterm labor, placenta previa, placental implantation, uterine rupture, hysterectomy, etc., it is generally not used. Patients should be advised to terminate the pregnancy at an early stage. 2. Methotrexate (MTX) treatment is suitable for all types of CSP in good general condition, and the most commonly used drug is MTX. (1) Systemic administration: Dose is calculated according to body weight of 1mg/kg or according to the surface area of the body, such as 50 mg/m2, and is injected intramuscularly in a single injection or multiple injections. Repeat once a week, if the drop of HCG is more than 50%, the drug should be stopped and observed; (2) Local application: The dose is 5-50mg, which is injected into the capsule or mass with a 16-20 needle; (3) Precautions for MTX treatment MTX treatment is effective, but the duration of the treatment is long, and there is a possibility of treatment failure. Severe uterine bleeding may occur at any time during the treatment and must be carried out in hospitals that have the conditions for further treatment; vaginal color Doppler ultrasound must be used during the drug treatment to monitor changes in blood flow signals around the gestational sac or mass, and blood HCG levels must be measured at regular intervals in order to understand the effect of the treatment. If the effect of treatment is satisfactory, the mass will shrink significantly and the blood flow will decrease or even disappear. Unsatisfactory decrease of blood HCG or persistence of high speed and low obstruction of blood flow signal suggests that the patient has poor response to the treatment, and the frequency or dose of drug treatment should be increased or the treatment method should be changed, and attention should be paid to the possibility of hemorrhage at any time; for CSP patients who are treated conservatively with MTX, after the decrease of blood HCG to 50IU/L or normal, the uterus can be cleared under the supervision of B ultrasound in order to shorten the treatment time and reduce the risk of hemorrhage; MTX has the effect of teratogenicity. MTX has a teratogenic effect and should be stopped for several months before pregnancy. Local puncture: It is suitable for those who are combined with intrauterine pregnancy at the same time and request to continue pregnancy. Use No.16-18 puncture needle to puncture the gestational sac, can simply suck the sac fluid, without other drug treatment; or directly puncture the fetal heart beat, can also be injected into the appropriate amount of potassium chloride, to promote the cessation of development of the embryo. (1) Negative pressure suction or curettage: suction or curettage for CSP often leads to severe and uncontrollable uterine bleeding, therefore, once CSP is identified, suction or curettage should not be done easily. In cases with shallow villous implantation, a small gestational sac growing into the uterine cavity, or after satisfactory MTX treatment, curettage can be performed under ultrasound monitoring. Preoperative first aid plan should be available, such as blood preparation, gauze tamponade, Foley’s ureter (18F) uterine insertion with local compression (30-90ml saline injection, retained for 12-24h), forceps cervix (3, 6, 9, 12 points) 90° rotation of the cervix, and uterine artery embolization, etc., to preserve the uterus as much as possible; (2) laparoscopic or open uterine partial incision to extract the capsule and suture surgery: under direct vision Under direct visualization, the pregnancy sac is removed and the wound is either directly sutured or the original scar is removed and re-sutured. There is a risk of hemorrhage with this procedure, so it should be used selectively. In patients with a large localized mass and abundant blood vessels, this procedure can be performed after uterine artery embolization; (3) uterine artery embolization: injection of an embolic agent into the uterine artery through a femoral artery cannula is rapid and effective in stopping bleeding. Gelatin sponge particles are the most commonly used absorbable embolic agent. Uterine artery embolization can be combined with MTX, i.e., a moderate amount of MTX is applied before or after the procedure to enhance the therapeutic effect. Twenty-four hours after uterine artery embolization, curettage is performed under B-ultrasound monitoring to remove as much of the fetal vesicle as possible and accelerate the absorption of the lesion. At this time, the operation is safe, with little bleeding, and the risk of uterine perforation can be reduced under ultrasound monitoring; (4) Internal iliac artery ligation or ligation of the upper and lower branches of the uterine artery: the ligation of the internal iliac artery is effective, but the ligation of the branches of the uterine artery is not always effective; (5) Subtotal hysterectomy or total hysterectomy: This is an emergency measure taken only in order to save the life of the patient due to a short period of hemorrhage, and when the conditions are limited and there is no other alternative feasible. (6) Follow-up After discharge from the hospital, patients should be followed up regularly with ultrasound and serum HCG examination until HCG is normal; 2. Women with reproductive requirements should be informed of the risk of CSP, late uterine rupture, and placenta implantation in the event of a second pregnancy; 3. Women with no reproductive requirements should immediately implement appropriate contraceptive measures. Guidelines for the diagnosis and treatment of cesarean section uterine incision keloid pregnancy (Chinese Medical Association, Family Planning Branch) A case of incision pregnancy was 1mm away from the plasma layer of the bladder, with almost no muscular layer, and the gestational sac was 10cm in size. The germ length was 26mm, and it had been treated with aminopterin. The uterine cavity was empty and the lower segment of the uterus was significantly enlarged with 4mm of myometrium in the posterior wall. There was abundant local blood flow.