Cesarean scar pregnancy (CSP) is a pregnancy in which the pregnant egg is implanted in the scar of the uterus after cesarean delivery. For more than 10 years, the incidence of CSP has been on the rise as the rate of cesarean delivery has been increasing year by year. If patients with CSP are not diagnosed early and treated appropriately, severe bleeding may occur and even hysterectomy may be possible, which can be life-threatening in severe cases and cause serious health damage to women. The risk of placental implantation, abdominal pregnancy, uterine rupture and hemorrhage is greatly increased if CSP continues into the middle and late stages of pregnancy. Therefore, in order to better diagnose and treat CSP and reduce its harm to women’s reproductive health, the Chinese Medical Association Family Planning Section has formulated the Consensus on the Diagnosis and Treatment of Cesarean Scar Pregnancy with reference to relevant literature at home and abroad, which is recommended to be implemented with reference by medical and family planning technical service institutions at all levels, and to accumulate experience and gradually improve in practice. I. Clinical typing of CSP There are two different forms of CSP, one is that the embryo sac is planted in the scar of the previous cesarean incision, but the whole grows toward the official cavity, with the possibility of continuing pregnancy, but often to the middle and late stages of complications such as placental implantation and severe bleeding. In the other case, the embryo sac is completely implanted in the scar defect and grows toward the bladder and abdominal cavity, and bleeding or even uterine rupture occurs in early pregnancy, which is extremely dangerous. (1) Uterine bleeding: Embryo sac abruption can cause uterine bleeding, because of the weak muscle layer and scar tissue at the place of implantation, poor contraction of the muscle wall, the broken blood vessels cannot be easily closed, bleeding is dripping or continuous, sometimes more and sometimes less, or sudden massive bleeding, even rapid as a spring, leading to blood pressure drop and shock. (2) Bleeding local stasis: bleeding mixed with the stopped developing embryo sac to form a mass, which increases with bleeding and eventually leads to uterine rupture and intra-abdominal bleeding. (3) Bleeding into the official cavity: expansion of bleeding into the uterine cavity can lead to accumulation of blood in the rich cavity, which can be easily misdiagnosed as embryonic abortion, inevitable miscarriage, incomplete miscarriage and gravidity. (4) Bleeding sludge in the cervical canal: bleeding does not flow out in time and sludge in the cervical canal, the cervical swelling, which can be misdiagnosed as cervical pregnancy, inevitable miscarriage, etc. 2. Continued development of embryo: (1) Early uterine rupture: the pregnant egg lays and develops deep in the scar fissure and breaks through the thin muscular layer due to the expansion of the sac cavity. Even the plasma membrane layer, resulting in uterine rupture and intra-abdominal bleeding. (2) Mid- and late-term hemorrhage: If the embryo sac continues to develop and grows toward the isthmus and official cavity, placenta previa, placenta implantation and a series of related mid- and late-term pregnancy and delivery complications will occur, such as late-term abortion, uterine rupture, and placenta non-detachment or hemorrhage on the detached surface after delivery. The clinical manifestations of cesarean scar pregnancy vary according to the depth of implantation of the embryo sac and the development of the embryo, and are not clearly specific. Ultrasonography is the main diagnostic basis. 1.History: history of cesarean delivery, onset is not related to the number of years after cesarean delivery and patient’s age. 2. Symptoms: (1) Early pregnancy reaction: the same as early pregnancy reaction of intrauterine pregnancy. (2) Vaginal bleeding: About half of the patients visit the clinic with vaginal bleeding, which is manifested in the following forms: ①Vaginal bleeding after menopause is constant, with little or menstrual-like bleeding, or suddenly increasing, or it may start with sudden heavy bleeding with large blood clots, blood pressure dropping, or even shock. ②Intraoperative or post-operative abortion: It is manifested as heavy bleeding during the operation, gushing and even difficult to control, with a drop in blood pressure or even shock within a short period of time. It can also be manifested as continuous or sudden increase of bleeding after the operation. ③After medication abortion: There is often no obvious tissue discharge or only a small amount of membrane-like tissue discharge after medication. Vaginal bleeding persists or suddenly increases after medication abortion, and heavy bleeding occurs when performing clearance surgery. (3) Accompanying symptoms: Most patients have no abdominal pain, and a few have mild abdominal pain. If there is more bleeding in a short time, symptoms of hemorrhagic shock may appear. (3) Physical signs: Most of them have no special physical signs, and the isthmus of the uterus is found to be enlarged during gynecological examination in individual cases. Transvaginal ultrasound is good for observing the size of the embryonic sac, the relationship with the cesarean scar and the thickness of the base layer between the embryonic sac and the bladder; transabdominal ultrasound is good for understanding the relationship between the embryonic sac or mass and the bladder and measuring the thickness of the local muscle layer to guide the treatment; the combination of the two types of ultrasound can provide a more comprehensive The combination of the two types of ultrasound can provide a more comprehensive understanding of the condition. The main features of ultrasound imaging are as follows: (1) the embryonic sac is not seen in the uterine cavity and cervical canal, and the endometrial line is visible. (2) The embryonic bursa is seen in the anterior wall scar of the isthmus or in a heterogeneous mass. ③The continuity of the myometrium at the scar is interrupted, the myometrium is thinned, and the interval with the bladder is narrowed. The CDFI and ultrasound images can help to diagnose and guide the treatment. (2) Blood B-Human chorionic gonadotropin (β-HCG) measurement: clinically, blood β-HCG measurement is useful for the diagnosis of pregnancy, but not for the diagnosis of CSP, and is mainly used to guide the choice of treatment and monitor the effect of treatment. (3) Other examinations: e.g. 3D ultrasound, MRI and laparoscopy, are generally not used as routine examination methods, but only in special difficult cases and when the diagnosis is difficult. IV. Differential diagnosis 1. Isthmus pregnancy: Pan refers to all pregnancies in which the pregnant egg is deposited in the isthmus of the uterus including the lateral or posterior wall, so there can be no history of cesarean delivery. The embryo sac grows towards the official cavity, the isthmus continuity is mostly uninterrupted, and the uterine morphology is basically normal. 2, Cervical pregnancy: the clinical presentation is similar to CSP and easily confused, relying mainly on ultrasound examination to identify it. In the case of cervical pregnancy, the cervical canal is uniformly enlarged so that the whole uterus is in the shape of a gourd with a small upper and a large lower part, and the lesion is confined to the cervix and does not exceed the internal opening. The embryonic sac-like echogenicity is visible in the cervical canal, and the embryonic bud and fetal heart are rarely seen, and the embryo mostly stops developing. If there is bleeding, it may be a heterogeneous medium or low echogenic mass. The endometrial line of the cavity is clear without the embryonic sac. The isthmus of the uterus is continuous and normal in structure. The differential diagnosis of early pregnancy is easy, but as the gestational months increase, the differential diagnosis between cervical pregnancy, CSP or isthmic pregnancy implanted in the lower uterine segment can be difficult. The diagnosis of refractory miscarriage in intra-uterine pregnancies: in refractory miscarriage, vaginal bleeding is often accompanied by paroxysmal abdominal pain that gradually worsens, and less often by severe and heavy bleeding. ultrasound imaging helps to identify the embryo sac, which is usually in the official cavity, but can also move to the lower part of the uterine cavity or even to the cervical canal, but is connected to the tissue in the official cavity. The uterine cavity may have blood accumulation, the internal cervical opening is mostly open, but the isthmus is not significantly enlarged and the anterior wall of the isthmus is continuous. The bleeding decreases significantly after expulsion of the embryo sac, the abdominal pain disappears, and the uterus soon returns to its normal shape on ultrasound follow-up. 4, Incomplete abortion of intra-uterine pregnancy: vaginal bleeding with tissue discharge, continuous bleeding thereafter, slight abdominal pain, ultrasound image shows uterine size less than the number of weeks of menopause, heterogeneous echogenicity in the cavity, also may be accompanied by liquid dark areas, no dilatation of the isthmus, local blood flow is not abundant, the anterior wall of the isthmus is continuous. Blood β-HCG decrease is more obvious. 5. Trophoblastic disease: CSP may be confused with staphylocytosis when there is intrauterine hemorrhage. The uterus can be significantly enlarged and soft in case of staphylocytosis, and the ultrasound image of the uterine cavity is mostly honeycomb or snowfall-like with heterogeneous echogenicity, and embryonic sac-like structures can be seen in partial staphylocytosis fashion without isthmus dilation and expansion, and the myometrium of the anterior wall of the uterus is continuous. In cases of CSP with embryonic abortion and uterine bleeding, the embryonic sac is no longer visible and there is a risk of misdiagnosis of choriocarcinoma with myxomatous infiltration. Choriocarcinoma is more likely to metastasize distantly, and blood beta-HCG levels are usually high and tend to increase. Regular follow-up ultrasound and blood β-HCG measurements, combined with medical history and examination of excreted tissues, will assist in the diagnosis. The goal of treatment is to terminate the pregnancy, remove the lesion, and ensure the safety of the patient. The principles of treatment are early detection, early treatment, reduction of complications, and avoidance of expectant treatment and blind scraping. The following treatment plan is provided according to the patient’s age, condition, ultrasound imaging, blood β-HCG level and requirements for fertility. The patient must be fully communicated with, fully informed of the disease and the risks of various treatments and sign an informed consent form before treatment. 1. Uterine artery embolization followed by uterine clearance: Injection of embolic agents into the uterine artery via a femoral artery cannula provides rapid and effective hemostasis. Gelatin sponge granules are the most commonly used absorbable embolic agent. Uterine artery embolization can be combined with methotrexate, i.e., an appropriate amount of methotrexate is injected intramuscularly before or after surgery or an appropriate amount of methotrexate is injected into the bilateral uterine arteries before embolization to enhance the therapeutic effect. After embolization of the uterine arteries, it is necessary to perform the clearance procedure under ultrasound surveillance, preferably within 3 d after the procedure, and ultrasound again before scraping to check the blood flow at the embryonic sac bed of the medaka. The risk of intraoperative hemorrhage is greatly reduced at this time, but one should still be prepared for resuscitation, especially if local blood flow is still abundant. The risk of uterine perforation can be reduced under ultrasound surveillance. 2. Ultrasound-supervised curettage: The curettage of CSP patients may lead to severe and uncontrollable uterine bleeding, therefore, it should not be done easily. For CSP with small embryo sacs, shallow chorionic villus implantation, local blood flow is not abundant, and blood β-HCG level is not high or growing into the uterine cavity, clearance can be performed under ultrasound surveillance. The operation should be performed in a hospital with conditions for blood transfusion and emergency open surgery, and a preoperative emergency plan should be available, such as blood preparation, local pressure hemostasis plan such as official gauze tamponade, Foley’s urinary catheter (18F) uterine insertion with local pressure injection of 30-90Inl saline and retention for 12-24h) and uterine artery embolization, etc. . 3.Clearance after methotrexate treatment: methotrexate is suitable for patients with good general condition, gestational age <8 weeks, ultrasound suggesting myometrial thickness between embryo sac and bladder wall <2mm, and serum β-HCG <5000 IU/L. After conservative treatment with methotrexate, clearance was performed under ultrasound supervision after the blood β-HCG dropped to normal. To shorten the treatment time and reduce the risk of hemorrhage. (1) Methotrexate administration: ① Systemic administration: the dose is calculated according to body weight 1ms/kg, or according to body surface area such as 50mg/n12, single or multiple intramuscular injections. Repeat once a week, blood β-HCG drop > 50%, stop the drug for observation. (2) Local application: the dose varies from 5-50mg and is injected intracapsularly or within the mass with a 16-20 gauge puncture needle. (2) Precautions for methotrexate treatment: Methotrexate treatment is effective, but the course of treatment is long and there is a possibility of treatment failure. Serious uterine bleeding may occur at any time during treatment and must be performed in a hospital that is equipped for further treatment; vaginal color Doppler ultrasound must be used to monitor changes in blood flow signals around the embryonic sac or mass during drug treatment, and blood β-HCG levels must be measured regularly to understand the effect of treatment. If the treatment effect is satisfactory, the mass is significantly reduced and the blood flow is significantly reduced or even disappeared. Unsatisfactory decrease of blood β-HCG or persistence of high speed and low obstruction blood flow signal suggest that the patient has poor response to treatment, the number of times or dose of drug treatment should be increased or the treatment method should be changed, and attention should be paid to the possibility of haemorrhage at any time old1; methotrexate has teratogenic effect, and it takes several months after treatment before another pregnancy can be carried out. 4. laparoscopic or open uterine partial excision and suturing: the embryonic sac is removed under direct vision and the wound is closed directly or the original scar is removed and re-sutured. This procedure carries a risk of haemorrhage and should therefore be performed selectively. This procedure can be performed after uterine artery embolization in patients who have formed a large local mass with abundant blood vessels. 5. Local puncture: The embryonic sac is punctured with a 16-18 gauge puncture needle and the sac fluid can be simply aspirated without other medication; or the fetal heartbeat can be directly punctured and an appropriate amount of potassium chloride can be injected to induce the embryo to stop developing. This method is more suitable for those who also have combined intrauterine pregnancy and want to continue the pregnancy. 6. Subtotal hysterectomy or total hysterectomy: This method is only an emergency measure to save the patient’s life due to short time hemorrhage, and there are no other feasible methods. VI. Follow-up Patients should be followed up regularly after discharge. Ultrasound and serum β-HCG examination should be performed until β-HCG is normal and the local mass disappears. The follow-up time and frequency will depend on the changes of the disease. For women with fertility requirements, it is recommended to have another pregnancy six months after cure, and to inform the risk of CSP, late pregnancy uterine rupture and placental implantation. For women without reproductive requirements, appropriate and effective contraceptive measures should be implemented promptly. After menstruation returns to normal, compounded short-acting oral contraceptive pills and intra-officer devices are recommended as contraceptive methods. The goal of this consensus is to raise the awareness of CSP among medical personnel at all levels, to achieve early detection and diagnosis of CSP, to provide timely treatment, and to reduce the incidence of CSP complications; to provide post-treatment family planning services and to avoid the recurrence of unintended pregnancy. In order to achieve these goals, we have developed a CSP consultation and treatment process, which is shown in the figure. The following four points are required when medical personnel attend to pregnant women with a history of cesarean delivery: (1) be aware of the risk of CSP and master the basic points of diagnosing CSP; (2) once CSP is diagnosed, refer to a hospital with conditions for inpatient treatment; (3) choose appropriate treatment measures according to the patient’s specific condition; (4) instruct the patient to implement appropriate contraceptive measures immediately after CSP is cured. The patient should apply for color ultrasound examination, and the application form should indicate a history of cesarean section delivery. It is necessary to know the embryo sac or placenta attachment site, and those who suspect CSP. Immediately admit to the hospital for treatment, and transfer to a higher level hospital after fully informing the condition if there is no diagnosis and treatment. Organize consultation with clinicians and ultrasonographers. If the diagnosis is difficult, 3D ultrasound is feasible, and the patient is fully informed of the condition and the effect of various treatment options, the risk of recurrence, and the treatment plan is discussed together.