EP01.36: Spotlight on impaired acoustic window: time to agree on a scientific definition

This study aimed to evaluate the impaired acoustic window (IAW) reported during the second and third trimester obstetric ultrasound scans. This retrospective observational study was conducted between April 2022 and February 2024. According to the viewpoint software, sonographers systematically reported their evaluation of the exam conditions as good or unsatisfactory. The study sample comprised 9036 consecutive and unselected obstetric scans, including 2547 (28.2%) level III, 2752 (30.5%) level II, and 3735 (41.3%) level I ultrasounds. All scans were performed using General Electric Medical Systems, Zipf, Austria machines. The ultrasound conditions were estimated to be good in 6787 scans (76.5%) and unsatisfactory because of an IAW in 1243 scans (14%). The individual reporting rates of IAW ranged from 7.6% to 55.6%. IAW was reported more frequently by midwives and residents than by doctors (18.3% vs. 12.6%, p < .001). IAW was significantly lower in the more than 10-years-experienced group than in the group with less than 5-years-experience (17% vs. 11%, p < .001). Multivariate regression analysis demonstrated that maternal obesity, gestational age, sonographer experience, and grade significantly contributed to IAW reporting. (R2 = 0.276, p < 0.001). This study revealed highly subjective reporting of an IAW. The lack of standardisation could lead to misuse of this term, indicating a need for further studies to enhance the understanding and grading of IAW.