Reducing intraoperative hemorrhage in type II caesarean scar pregnancy: a study protocol comparing high-intensity focused ultrasound (HIFU) pretreatment vs. hysteroscopy-guided suction curettage-an open-label, 1:1 parallel-group, superiority-design investigator-initiated trial (IIT).

Following participant recruitment, a trained researcher will collect baseline data. This dataset will include key participant characteristics, such as age, parity, gravidity, number of prior caesarean deliveries, interval since the last caesarean delivery, fertility intentions, history of caesarean scar pregnancy (CSP) or placenta accreta spectrum (PAS), gestational age at admission, gestational sac (GS) size, presence of foetal cardiac activity, residual myometrial thickness (RMT), serum β-hCG levels, and clinical symptoms (e.g. vaginal bleeding or lower abdominal pain). Clinical outcome data will encompass: uterine depth; pituitrin administration and Foley catheter balloon placement; intraoperative blood loss; presence/absence of intrauterine adhesions; surgical duration; length of hospitalization (calculated as discharge date minus admission date); post-treatment vaginal bleeding duration; time to β-hCG normalization; resumption of normal menstruation; and pregnancy outcomes. Data related to HIFU treatment will include total ablation energy, total treatment time, median treatment power, sonication time, and treatment intensity. Safety indicators will include intraoperative complications (e.g. uterine perforation, water intoxication, massive haemorrhage, or surgical procedure modification) and HIFU treatment complications (e.g. lower abdominal pain, sciatica or gluteal pain, haematuria, skin injury, and nerve injury). Adverse events (AEs) will be graded for severity—from mild to moderate (Grades 1–2) to severe (Grades 3–5)—according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0 criteria [ 25 ]. The results of the ultrasound examination will be reviewed and approved by two experienced physicians, while the laboratory tests will be conducted by the hospital’s qualified laboratory department. Emphasize the importance of follow-up through repeated communications prior to discharge. Remind participants to attend follow-up appointments via the official WeChat account and hospital follow-up system. Streamline the workflow with advanced scheduling, enabling participants to select weekend or off-peak hours for follow-up visits. Emphasize the importance of follow-up through repeated communications prior to discharge. Remind participants to attend follow-up appointments via the official WeChat account and hospital follow-up system. Streamline the workflow with advanced scheduling, enabling participants to select weekend or off-peak hours for follow-up visits. Research data will be stored in Microsoft Excel files on hospital intranet computers, which are password-encrypted and accessible only to authorized researchers. During data collection and management, researchers will ensure meticulous, timely, accurate, and comprehensive documentation of all relevant study data. Data will undergo regular checks by the quality controller, and participant personal information will not be recorded. Each participant will be assigned a unique study number, which will be utilized across all study-related documentation. Such documentation will remain accessible exclusively to the study investigators. N/a.

The protocol versionand date: V-1.0 29th May, 2020. The recruitment began on July 12, 2020, and the recruitment work has been completed, but the follow-up of some participants’ secondary assessment indicators (the pregnancy outcomes within two years) has not yet been carried out.

The trial will be conducted at Qingdao Women and Children’s Hospital. The diagnostic criteria for caesarean scar pregnancy will be confirmed through transvaginal ultrasound examination [ 3 ]. The ultrasound diagnostic report will be reviewed and finalized by two ultrasound physicians. Diagnostic criteria of CSP [ 5 ]: An empty uterine cavity and endocervix. A thin or absent layer of myometrium between the GS and the bladder. GS located anteriorly at the level of the internal os covering the previous lower uterine segment caesarean section scar. An abundant peritrophoblastic blood flow within the area of the GS, as demonstrated by low-pulse repetition Doppler study. An empty uterine cavity and endocervix. A thin or absent layer of myometrium between the GS and the bladder. GS located anteriorly at the level of the internal os covering the previous lower uterine segment caesarean section scar. An abundant peritrophoblastic blood flow within the area of the GS, as demonstrated by low-pulse repetition Doppler study. Diagnostic criteria of type II CSP [ 5 ]: The gestational sac is partially implanted at the uterine scar site, with a portion or the majority of it lying within the uterine cavity; in rare instances, it may even extend to the fundal region of the uterine cavity. The gestational sac is notably deformed and elongated, with its lower pole forming an acute angle. The myometrium between the gestational sac and the bladder is thinned out, measuring ≤ 3 mm in thickness; CDFI (Color Doppler Flow Imaging): Trophoblastic blood flow signals (low-resistance blood flow) are detected at the site of the uterine scar. The gestational sac is partially implanted at the uterine scar site, with a portion or the majority of it lying within the uterine cavity; in rare instances, it may even extend to the fundal region of the uterine cavity. The gestational sac is notably deformed and elongated, with its lower pole forming an acute angle. The myometrium between the gestational sac and the bladder is thinned out, measuring ≤ 3 mm in thickness; CDFI (Color Doppler Flow Imaging): Trophoblastic blood flow signals (low-resistance blood flow) are detected at the site of the uterine scar. All participants must be at least 18 years old and must voluntarily decide to terminate their pregnancy and sign the surgical informed consent form. Participants with a history of caesarean section. Participants who have experienced menopause (within eight weeks) and have serum β-hCG levels exceeding 10,000 mIU/mL. The maximum diameter of the gestational sac is less than 50 mm [ 21 ]. Participants must voluntarily agree to participate in this study and sign an informed consent form. All participants must be at least 18 years old and must voluntarily decide to terminate their pregnancy and sign the surgical informed consent form. Participants with a history of caesarean section. Participants who have experienced menopause (within eight weeks) and have serum β-hCG levels exceeding 10,000 mIU/mL. The maximum diameter of the gestational sac is less than 50 mm [ 21 ]. Participants must voluntarily agree to participate in this study and sign an informed consent form. Participants with vaginitis or vaginal bleeding exceeding menstrual volume before interventions. Participants with severe coagulation dysfunction, severe internal or external diseases, or contraindications to anaesthesia. Participants with a history of allergy to contrast agents. Participants who are lactating. Participants who do not want to receive surgical treatment. The other types of CSP. Participants with vaginitis or vaginal bleeding exceeding menstrual volume before interventions. Participants with severe coagulation dysfunction, severe internal or external diseases, or contraindications to anaesthesia. Participants with a history of allergy to contrast agents. Participants who are lactating. Participants who do not want to receive surgical treatment. The other types of CSP. Informed consent will be obtained from authorized investigators, who are required to have more than 6 years of experience in performing induced abortion surgery. N/a.

Qingdao Women and Children’s Hospital Ethics Committee and the State Key Laboratory of Ultrasound in Medicine and Engineering Academic Committee. A Data Monitoring Committee (DSM) composed of one clinician, one statistician, and the secretary of the Ethics Committee of Qingdao Women and Children’s Hospital will be established. DSM members will conduct regular study monitoring, with the process maintained independently from investigators. All AEs shall be collected, managed proactively in line with established treatment protocols, and serious adverse events (SAEs) reported to the Qingdao Women and Children’s Hospital Ethics Committee in a timely manner. The frequency and procedures for auditing trial conduct will be annual, and the audit process will be independent of the investigators. The communication plan for protocol amendments will be developed by researchers, formulated in accordance with internal hospital procedures and Good Clinical Practice (GCP) requirements. This plan aims to ensure transparent dissemination of amendment information to all relevant stakeholders, thereby safeguarding the study’s scientific validity as well as the rights and interests of trial participants.

Blinding was not applicable, as this was an open-label study. N/a.

In clinical practice, our primary goal has consistently been to identify safe, effective, minimally invasive, and fertility-preserving treatment modalities for participants with CSPs. Treatment decisions must be customized individually, considering the severity of symptoms, future family planning goals, physician expertise, and institutional resources. Hysteroscopy has demonstrated a relatively high success rate in treating type I CSP, with surgical bleeding effectively controlled [ 23 ]. However, the risk of complications, particularly massive haemorrhage, is heightened during hysteroscopic treatment, especially in grassroots-level hospitals or among physicians with limited clinical experience. HIFU delivers energy precisely to the implantation site of the GS at the caesarean scar through real-time ultrasound monitoring. It destroys trophoblastic cells and damages small blood vessels with diameters less than 2 mm by generating temperatures of 60–100 ℃ [ 13 ]. No statistically significant difference was observed between HIFU and UAE in terms of treatment success rate [ 14 , 16 ]. Furthermore, HIFU has a reduced impact on post-operative menstrual blood loss (MBL), making it a favourable treatment option for participants with fertility intentions [ 19 , 20 ]. Therefore, in this randomized clinical trial, our primary objective will be to assess the necessity of HIFU as a treatment option for type II CSP to control intraoperative blood loss. Characteristics such as gestational age, size of the gestational sac, RMT, and pre-treatment serum β-hCG levels are identified as risk factors associated with intraoperative blood loss [ 26 ]. Subsequently, we will analyze these characteristics and develop classifications to optimize the treatment strategy.

High-intensity focused ultrasound pretreatment combined with hysteroscopy-guided suction curettage reduces intraoperative bleeding in type II caesarean scar pregnancy.

Per-protocol analyses will be conducted. Intercurrent events include: study-unrelated events (such as upper respiratory tract infection) occurring during participants’ hospitalization leading to prolonged length of hospital stay, and unplanned pregnancy occurring before the resumption of postoperative menstruation leading to inability to track menstrual resumption time. The secondary outcome indicators of such participants will not be included in the statistical analysis. To be included in the analysis, a participant must provide data from the baseline and the intraoperative blood loss. If a participant meets the withdrawal criteria, no data will be included in the analysis. Normally distributed quantitative data will be expressed as mean and SD. Non-normally distributed variables will be expressed as median (interquartile range). Qualitative data will be expressed as counts and percentages. Comparisons between groups will be conducted using the Student’s t -test, Wilcoxon rank test, or χ 2 test. Two-sided p  < 0.05 will be considered statistically significant. Given the low risk associated with the study content, interim analysis will not be conducted. N/a. Per-protocol analyses will be conducted. Missing data will be handled using multiple imputation. Results derived from complete-case data (without missing observations) will be compared with those from imputed data to conduct a sensitivity analysis. The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request 3 months after the official publication of the research paper.

Caesarean scar pregnancy (CSP) is a unique type of ectopic pregnancy in which the gestational sac (GS) is implanted into the scar tissue from a previous caesarean delivery [ 1 , 2 ]. The estimated incidence of CSP ranges from 1 in 1800 to 1 in 2216 pregnancies [ 3 , 4 ]. The rising caesarean delivery rate and the increasing use of reliable imaging techniques for CSP diagnosis have led to a significant increase in reported cases over the last decade. CSP is associated with a high incidence of severe maternal morbidity, such as life-threatening haemorrhage, placenta accreta spectrum (PAS), uterine rupture, and even maternal mortality. Achieving optimal management of CSP remains a significant challenge for gynaecologists. The Gynaecology Subcommittee of the Chinese Medical Association issued updated guidelines in the Expert Opinion of Diagnosis and Treatment of Caesarean Scar Pregnancy in 2016 [ 5 ]. The treatment principles for CSP are early detection, early diagnosis, and early intervention. The guidelines classify CSP into three types—type I, type II, and type III—based on the growth direction of the gestational sac (GS) and the residual myometrium thickness (RMT) between the GS and the bladder, as assessed by ultrasound, with specific treatment recommendations provided for each type. For type I CSP, ultrasound-guided suction curettage exhibits favourable therapeutic outcomes with a relatively low risk of massive haemorrhage. For type III CSP, the risk of residual tissue retention and bleeding during curettage is high, making this procedure unsuitable. Alternatively, pregnancy tissue removal combined with uterine scar repair may be considered. For type II, GS is partially implanted in the uterine scar, and the RMT is less than 3 mm. Despite the availability of various treatment modalities—including medication, dilation and curettage, hysteroscopic and laparoscopic surgery, uterine artery embolization (UAE), high-intensity focused ultrasound (HIFU), and combinations of these approaches—significant risks of complications remain, even when strategies are tailored to individual participants and clinical manifestations. Mounting evidence indicates that CSP is a precursor to abnormally adherent placenta in the second and third trimesters [ 3 ], increasing the risk of severe haemorrhage or hysterectomy during operation or delivery. Surgical hysteroscopy provides direct visualization of the competent detachment of the decidua basalis from the steep concavity of the caesarean scar defect (CSD) in CSP. Hysteroscopic surgery has been reported to achieve a high success rate and low complication rate in CSP, particularly in cases with RMT greater than 3 mm [ 6 , 7 ]. However, patients with RMT < 3 mm undergoing hysteroscopic surgery or curettage may encounter intraoperative uncontrollable bleeding accompanied by a high incidence of required secondary treatment [ 8 ]. Pre-assessment of blood loss in CSP is crucial for gynaecologists. Effective preoperative management is essential to minimize the risk of excessive bleeding during surgery. HIFU ablation, a novel non-invasive treatment, has been widely employed in the treatment of various solid tumours and benign disorders, particularly gynaecological diseases, such as uterine fibroids and adenomyosis [ 9 – 12 ]. During HIFU ablation, ultrasound beams generated by the transducer penetrate through the abdominal skin, subcutaneous tissue, and bladder before focusing on the targeted tissue around the CSP lesion. Coagulative necrosis occurs when the target temperature increases to over 60 °C. The cavitation effect of HIFU may also loosen the adhesion between the GS and the myometrium at the uterine scar [ 13 ]. Numerous recent studies have demonstrated that HIFU is an effective therapeutic option for participants with type I, II, and III CSP [ 14 , 15 ], reducing intraoperative blood loss [ 14 , 16 ]. In comparison with UAE, HIFU treatment for CSP offers advantages such as lower pain scores, fewer adverse effects, and minimal impact on post-operative menstrual blood loss [ 17 , 18 ]. HIFU is a favourable treatment option for participants with fertility preservation requirements [ 19 , 20 ]. However, HIFU may not be necessary in cases with a low risk of massive haemorrhage. To date, no randomized controlled trials (RCTs) have evaluated intraoperative blood loss and postoperative outcomes of surgical modalities—including suction curettage and hysteroscopy, with or without HIFU pretreatment—in women with type II CSP. Herein, we aim to conduct a prospective RCT to primarily evaluate the necessity of HIFU in the management of type II CSP.

Data collection is anticipated to be finalized by June 2026. Research findings will be published in alignment with agreements with the funding body and institutional guidelines. Upon acceptance of the research findings for publication, the relevant data will be made publicly accessible via the website at http://www.cpc.unc.edu/projects/china .

Eligible participants will be randomly assigned to the control or HIFU groups. The control group will undergo suction curettage guided by hysteroscopy, while the HIFU group will receive HIFU therapy followed by suction curettage guided by hysteroscopy. The HIFU treatment will use a JC200 focused ultrasound tumour therapeutic system (Chongqing Haifu Medical Technology Co. Ltd., Chongqing, P.R. China), which offers real-time sonographic monitoring. Participants will be instructed to undergo bowel preparation, which includes consuming semi-liquid and liquid foods, taking polyethylene glycol (PEG) orally the night before treatment, fasting for 6–8 h, and abstaining from drinking fluids for 2–4 h before the procedure. The abdominal wall, from the umbilicus to the upper margin of the pubic symphysis, must be shaved, degreased with 75% ethanol, and degassed using degassed water. A catheter will be inserted into the bladder for volume control. HIFU treatment will be performed by two experienced doctors who have completed over 200 HIFU procedures. During the procedure, participants will be placed in the prone position on the high-intensity focused ultrasound treatment table, with the anterior abdomen in contact with the degassed water. The sagittal ultrasound scanning mode will be used for pre-treatment planning and sonication. A water balloon will be placed between the transducer and abdominal wall to displace the bowel from the acoustic pathway. The point-by-point scan mode will be selected, with the power set between 350 and 400 W. The focus will be adjusted to target the embedding area of the GS, which will be treated from deep to superficial layers. Criteria for terminating HIFU treatment include the following: (1) Significant large-scale changes or generalized changes observed via real-time ultrasound monitoring; (2) Color Doppler showing a reduction in blood flow grading of the embedding area to grade 0 or grade 1 (Adler grading). A contrast-enhanced ultrasound using a microbubble agent (Sonovue, Bracco, Milan, Italy) will be performed 10 min before and immediately after HIFU to evaluate blood supply alterations in the embedding area. The bladder will be infused with cold saline (0–4 °C) to lower the local temperature immediately after HIFU, after which the urinary catheter may be removed. All participants will undergo pre-surgical preparation, including blood transfusion and the establishment of dual intravenous channels, and will be primed for potential conversion to laparoscopic or open surgery if necessary. The surgery will be performed by a single surgeon with extensive experience, including over 10 years in hysteroscopic surgery and more than 100 cases of hysteroscopic treatment for CSP. Participants in the HIFU group will undergo curettage guided by hysteroscopy within 0 to 1 day after HIFU ablation. The procedure will be performed under general anaesthesia. A prostaglandin drug (Carboprost suppositories, 1 mg, NORTHEAST PHARM) is inserted into the vagina 30 min before surgery to prepare the cervix. Participants empty their bladder and are placed in the lithotomy position. After sufficient cervical dilation, an 8-mm suction cannula will be gently inserted into the uterine cavity, and the vacuum pressure will be set at 400 mmHg. The cannula will be carefully maneuvered around the GS embedding area to detach the pregnancy tissues. The suction will be applied for 3 to 5 min. Following tissue aspiration, oxytocin (10 U in 500 mL of 0.9% NaCl, 60 drops/min) will be administered intravenously to promote uterine contractions. A 10-mm electrosurgical hysteroscope with 0.9% NaCl will subsequently be inserted into the uterine cavity. The uterine distention fluid will be injected into the cavity at a pressure ranging from 80 to 100 mmHg. The surgeon will perform a thorough examination of the uterine cavity and subsequently withdraw the hysteroscope to the CSD. The scar flap will be excised electrically with a ring electrode to fully expose the bottom of the incision (Fig.  2 ). The CSD will be examined systematically in a clockwise or counterclockwise direction. A wire-loop electrode may be utilized to remove retained pregnancy tissues, and electrocoagulation will be employed to control bleeding from the wound surface. If necessary, and provided there are no contraindications to anaesthesia, dilute vasopressin (6 U in 60 mL of 0.9% NaCl) will be injected into the cervix at the 4 o’clock and 8 o’clock positions, with a total volume of 20–60 mL, to control perioperative blood loss. If active uterine bleeding occurs, a Foley catheter balloon injected with normal saline will be promptly employed. Fig. 2 Crucial surgical procedures of hysteroscopy treatment. A Observation of the uterine cavity. B Observation of CSD. C Implantation site of the villi in CSD. D – F Scar flap of CSD. Abbreviation: CSD caesarean scar defect Crucial surgical procedures of hysteroscopy treatment. A Observation of the uterine cavity. B Observation of CSD. C Implantation site of the villi in CSD. D – F Scar flap of CSD. Abbreviation: CSD caesarean scar defect For intraoperative active bleeding that is unresponsive to conservative treatment, timely combined use of laparoscopy or UAE is required. For cases where postoperative HCG decreases slowly or rises again after a decrease, and ultrasonic examination reveals a lesion at the scar site, re-hospitalization for supplementary drug (Methotrexate, MTX) treatment or repeat hysteroscopic surgery is necessary. For intraoperative active bleeding that is unresponsive to conservative treatment, timely combined use of laparoscopy or UAE is required. For cases where postoperative HCG decreases slowly or rises again after a decrease, and ultrasonic examination reveals a lesion at the scar site, re-hospitalization for supplementary drug (Methotrexate, MTX) treatment or repeat hysteroscopic surgery is necessary. Participants will be withdrawn from the study, and no further data will be collected if they meet the following criteria: Participant experiencing an emergency, such as severe bleeding or intense pain before interventions required by the study, will be withdrawn from this study and carry out intervention immediately, such as UAE. Unexpected cancellation of surgery. Intraoperatively, the surgical approach is modified as needed (e.g. by incorporating laparoscopy or UAE). Postoperative pathology indicates gestational trophoblastic neoplasm. Participant asks to withdraw from the study. Participant experiencing an emergency, such as severe bleeding or intense pain before interventions required by the study, will be withdrawn from this study and carry out intervention immediately, such as UAE. Unexpected cancellation of surgery. Intraoperatively, the surgical approach is modified as needed (e.g. by incorporating laparoscopy or UAE). Postoperative pathology indicates gestational trophoblastic neoplasm. Participant asks to withdraw from the study. Pre-trial training All study personnel (including nursing staff) will complete standardized training prior to trial initiation. Training modules covered: study protocol and standard operating procedures (SOPs)/operational steps and safety precautions/data collection methodology/completion of case report forms (CRFs)/use of Excel-based data collection templates. In-trial process optimization Progress monitoring: Regular team meetings will be held to review trial progress, troubleshoot operational challenges, and implement workflow refinements to enhance efficiency and data quality. Pre-trial training All study personnel (including nursing staff) will complete standardized training prior to trial initiation. Training modules covered: study protocol and standard operating procedures (SOPs)/operational steps and safety precautions/data collection methodology/completion of case report forms (CRFs)/use of Excel-based data collection templates. In-trial process optimization Progress monitoring: Regular team meetings will be held to review trial progress, troubleshoot operational challenges, and implement workflow refinements to enhance efficiency and data quality. If active uterine bleeding occurs, dilute vasopressin and/or a Foley catheter balloon injected with normal saline will be permitted. Drug treatment (mifepristone or MTX) before surgery or before discharge after surgery is prohibited. N/a. Intraoperative blood loss. Ratio of near haemorrhage *Near haemorrhage is defined as any of the following: an estimated intraoperative blood loss of ≥ 100 mL [ 20 ], the utilization of a Foley catheter balloon [ 22 ], or a discrepancy in haemoglobin levels before and after the surgical intervention of ≥ 20 g/L [ 23 ].  Therapeutic success rates Success is defined as the complete removal of pregnancy tissue, normalization of serum β-hCG levels, and no need for readmission. Subsequent pregnancy outcomes within a 2-year follow-up period. Ratio of near haemorrhage *Near haemorrhage is defined as any of the following: an estimated intraoperative blood loss of ≥ 100 mL [ 20 ], the utilization of a Foley catheter balloon [ 22 ], or a discrepancy in haemoglobin levels before and after the surgical intervention of ≥ 20 g/L [ 23 ]. Therapeutic success rates Success is defined as the complete removal of pregnancy tissue, normalization of serum β-hCG levels, and no need for readmission. Subsequent pregnancy outcomes within a 2-year follow-up period. Hospitalization duration, intraoperative complications*, duration of vaginal bleeding after treatment, time to achieve normal β-hCG levels, and time to normal menstrual recovery. *Intraoperative complications include sacrococcygeal pain, treatment area pain, haematuria, fluid overload, symptomatic dilutional hyponatremia, uterine perforation, or hysterectomy. Once participants have signed the informed consent form and completed the review of inclusion and exclusion criteria, preoperative preparation will commence. Participants in the HIFU group will undergo hysteroscopic surgery 24 h after HIFU treatment. On the first postoperative day, blood routine and β-HCG levels will be rechecked. If no special conditions occur, patients will be discharged on the 2nd postoperative day. Following discharge, β-HCG levels will be tested weekly until they return to normal. Ultrasound re-examination will be performed after menstruation concludes. Strict contraception will be required for six months postoperatively. For participants with fertility intentions, a follow-up call will be made two years postoperatively to inquire about pregnancy outcomes (Fig.  3 ). Fig. 3 SPIRIT figure SPIRIT figure The primary outcome of this study is the intraoperative blood loss. The mean intraoperative blood loss for type II CSP treated with suction curettage under hysteroscopic guidance was 32.56 mL (standard deviation (SD) of 25.32 mL) [ 24 ], compared to 20.6 mL (SD of 21.8 mL) for cases treated with HIFU followed by suction curettage under hysteroscopic guidance between November 2019 and May 2020 at Qingdao Women and Children’s Hospital. Using an independent sample t -test with a type I error rate of 5% and a type II error rate of 20%, the calculated sample size per group was 63. Considering a 10% attrition rate, we will need 70 participants for each group (63/0.9). Attrition factors include withdrawal during the study period, loss to follow-up, non-compliance with study protocols, and invalid or unreliable recorded data. Consequently, this randomized clinical trial is designed to recruit a total of 140 participants diagnosed with type II CSP, who will be randomly assigned to two equally sized groups. Recruitment will be carried out through multiple approaches, including direct outreach to potential participants via outpatient clinics and departmental promotion at Qingdao Women and Children’s Hospital, as well as referrals from community hospitals. Participants diagnosed with type II CSP will be identified via medical record.

Note: the numbers in curly brackets in this protocol refer to SPIRIT checklist item numbers. The order of the items has been modified to group similar items (see http://www.equator-network.org/reporting-guidelines/spirit-2013-statement-defining-standard-protocol-items-for-clinical-trials/ ) Title {1} Reducing Intraoperative Hemorrhage in Type II Caesarean Scar Pregnancy: A Study Protocol Comparing High-Intensity Focused Ultrasound (HIFU) Pretreatment vs. Hysteroscopy-Guided Suction Curettage—An Open-Label, 1:1 Parallel-Group, Superiority-Design Investigator-Initiated Trial (IIT) Trial registration {2a and 2b}. Registration number: ChiCTR2000034332 Registry name: A randomized controlled clinical trial for the effect of FUAS combined with suction curettage and simple suction curettage in the treatment of type II cesarean scar pregnancy Protocol version {3} Version and Date: V-1.0 29th May, 2020 Funding {4} Foundation of the State Key Laboratory of Ultrasound in Medicine and Engineering (Grant No:2020KFA3002) Author details {5a} a State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing, 400,016, China; b School of Public Health and Management, Chongqing Medical University, Chongqing, P.R. China; c Qingdao Women and Children’s Hospital, Qingdao, Shandong, P.R. China Name and contact information for the trial sponsor {5b} Zhibiao Wang, e-mail: [email protected], State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing, 400,016, China Shuping Zhao, e-mail: [email protected], State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing, 400,016, China; Qingdao Women and Children’s Hospital, Qingdao, Shandong, P.R. China Role of sponsor {5c} The role of funding sources in the study design process, encompassing data collection, management, analysis, and interpretation; report writing; and the decision to submit the report for publication—including the ultimate authority over these activities. Note: the numbers in curly brackets in this protocol refer to SPIRIT checklist item numbers. The order of the items has been modified to group similar items (see http://www.equator-network.org/reporting-guidelines/spirit-2013-statement-defining-standard-protocol-items-for-clinical-trials/ ) Registration number: ChiCTR2000034332 Registry name: A randomized controlled clinical trial for the effect of FUAS combined with suction curettage and simple suction curettage in the treatment of type II cesarean scar pregnancy Zhibiao Wang, e-mail: [email protected], State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing, 400,016, China Shuping Zhao, e-mail: [email protected], State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing, 400,016, China; Qingdao Women and Children’s Hospital, Qingdao, Shandong, P.R. China