Fetal Turner Syndrome Nuchal

A 24-year-old primigravida presents for first-trimester combined screening at 13 weeks and 1 day of gestation. Transabdominal ultrasound demonstrates a live fetus with crown-rump length appropriate for dates. The structure marked **B** in the diagram shows a large bilobed cystic collection with internal linear septations extending from the occiput to the upper thorax, accompanied by diffuse skin edema greater than 5 mm, bilateral pleural effusions, and ascites. The three-vessel-trachea view reveals a narrowed transverse aortic arch. Karyotyping confirms 45,X monosomy. Which of the following best describes the ultrasound findings most characteristic of this diagnosis?