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

A recent study aimed to design a standardized sonographic evaluation and reporting system for Cesarean scar pregnancy (CSP) in the first trimester, for use by both general gynecology and expert clinics.

The study utilized a modified Delphi procedure and invited 28 international obstetric and gynecological ultrasonography experts who had extensive ultrasound experience to evaluate Cesarean section (CS) scars in early pregnancy and/or publications concerning CSP or niche evaluation. The study determined relevant items for detecting and assessing CSP based on the literature search results. The predefined consensus was a level of agreement of at least 70% for each item and a minimum of three Delphi rounds (two online questionnaires and one group meeting).

16 experts participated in the Delphi study and performed four Delphi rounds. They determined 58 relevant items and differentiated basic measurements for general practice and advanced measures for expert centers or research purposes. The experts agreed on all 58 items on the definition, terminology, and relevant articles for evaluating and reporting CSP. Further, they also developed advice on indications for referral to an expert clinic. 

They recommended that the first CS scar evaluation to determine the location of the pregnancy should be performed at 6-7 weeks' gestation using transvaginal ultrasound. Magnetic resonance imaging did not add value in diagnosing CSP (defined as a pregnancy with implantation in close contact with the niche). They agreed that a CSP could occur only when a niche is present and not with a healed CS scar. Relevant sonographic items to record included:

• Gestational sac (GS) size.
• Vascularity.
• Location with the uterine vessels.
• The thickness of the residual myometrium and location of the pregnancy concerning the uterine cavity and serosa.

Classification of CSP according to its location can be done as:

1. CSP in which the most significant part of the GS protrudes towards the uterine cavity.
2. CSP in which the largest part of the GS is embedded in the myometrium, not crossing the serosal contour.
3. CSP in which the GS is located partially beyond the outer contour of the cervix or uterus.

The type of CSP may variate with advancing gestation. Future studies are required to validate this reporting system and the value of the different CSP types.

Thus, the experts achieved a consensus regarding the sonographic evaluation and reporting of CSP in the first trimester. 

Jordans IPM, Verberkt C, De Leeuw RA, Bilardo CM, Van Den Bosch T, Bourne T, Brölmann HAM, Dueholm M, Hehenkamp WJK, Jastrow N, Jurkovic D, Kaelin Agten A, Mashiach R, Naji O, Pajkrt E, Timmerman D, Vikhareva O, Van Der Voet LF, Huirne JAF. Definition and sonographic reporting system for Cesarean scar pregnancy in early gestation: modified Delphi method. Ultrasound Obstet Gynecol. 2022 Apr;59(4):437-449. doi: 10.1002/uog.24815. PMID: 34779085; PMCID: PMC9322566.