The goal of this observational study is to determine whether the subjective assessment of the quality of obstetrical ultrasonography pictures can be similar to that of an objective tool.

The main question it aims to answer is:

Is the subjective assessment of the quality of obstetrical ultrasonography pictures by a young practitioner and an experienced one can be similar to that of an objective tool, such as the contrast-to-noise ratio (CNR)? The contrast-to-noise ratio is commonly used in radiology to evaluate image quality by assessing the ability to distinguish differences between two elements.

The investigators selected a retrospective cohort of 198 patients, including three pictures per fetus screened between 18 and 18 weeks and 6 days. For each picture, the investigators assessed the quality of two different elements and the entire image, and then calculated the CNR using software. The investigators will compare the three assessment between them

Inclusion Criteria:

• Patient who underwent ultrasound between 18 weeks and 18 weeks + 6 days for prenatal diagnosis
• Ultrasound performed by the same practitioner
• Ultrasound performed on the same ultrasound machine "Voluson E10", with the "RM6C" probe

Exclusion Criteria:

• Patient's refusal
• Use of another ultrasound device other than the "Voluson E10", and/or an ultrasound probe other than the "RM6C"
• Intrauterine fetal deaths

Women having undergone an ultrasound between 18 weeks and 18 weeks + 6 days at the Multidisciplinary Prenatal Diagnostic Center of Poitiers University Hospital