Definition and sonographic reporting system for Cesarean scar pregnancy in early pregnancy: modified Delphi method.

OBJECTIVE To develop a standardized sonographic evaluation and reporting system for a cesarean scar pregnancy (CSP) in the first trimester for both general gynecology and expert clinic. METHODS A modified Delphi procedure. Twenty-eight experts in obstetrics and gynecology ultrasonography were invited to participate. Extensive experience in the use of ultrasound to evaluate cesarean section scars in early pregnancy and/or publications concerning CSP or niche evaluation was required to participate. Relevant items for detection and evaluation of CSP were determined based on the results of a literature search. Consensus was predefined as a level of agreement on at least 70% per item, and minimum of three Delphi rounds were planned (two online questionnaires and one group meeting). RESULTS Sixteen experts participated in the Delphi study and four Delphi rounds were performed. In total 58 items were identified to be relevant. We differentiated between basic measurements to be performed in general practice and advanced measurement for expert centers or for research purposes. The panel also formulated advice on indications for referral to an expert clinic. Consensus was reached for all 58 items on the definition, terminology, relevant items for evaluation and reporting of CSP. First cesarean scar evaluation to determine the location of the pregnancy is recommended to be performed at 6-7 weeks of pregnancy using transvaginal ultrasound. MRI is not needed. It was agreed that a CSP is defined as pregnancies with implantation in or in close contact with the niche. Relevant items to register include gestational size, vascularity, localization in relation to uterine vascularity, thickness of the residual myometrium and its localization in relation to the uterine cavity and serosa. According to its localization a CSP can be reported as: (1) CSP in which the largest part of the GS protrudes towards the uterine cavity; (2) CSP in which the largest part of the GS is embedded in the myometrium; and (3) CSP in which the GS is partially located outside the outer contour of the cervix or uterus. Type of CSP may change with advancing gestation. Future studies are needed to validate this reporting system and the value of the different CSP types. CONCLUSION Satisfactory consensus amongst experts was achieved regarding the sonographic evaluation of the uterine scar and CSP. This article is protected by copyright. All rights reserved.