The objective of this observational study is to identify maternal and fetal characteristics that impact image quality in prenatal ultrasonography. The investigators have assembled a retrospective cohort of 198 patients, each contributing three ultrasound images taken between 18 and 18 weeks and 6 days of gestation. For each image, the investigators assess the quality of two distinct elements as well as the overall image through both subjective and objective evaluations.

The primary questions the study seeks to address are:

What maternal and fetal characteristics influence image quality in prenatal ultrasonography?

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