Which ultrasound finding indicates conditions like Turner's syndrome and Noonan syndrome?

Cystic hygroma is an ultrasound finding that is particularly associated with conditions such as Turner syndrome and Noonan syndrome. This abnormal collection of fluid, typically located at the back of the neck or along the spine, can be detected during routine prenatal ultrasound screenings.

The presence of cystic hygroma suggests chromosomal abnormalities, which is why it is closely linked to Turner syndrome, where there is a partial or complete absence of one of the X chromosomes (45,X), and Noonan syndrome, which is caused by mutations in genes that are involved in cellular signaling and growth. The association of cystic hygroma with these syndromes signals a need for further diagnostic evaluation, such as karyotyping or genetic testing, to confirm any underlying genetic conditions.

In contrast, conditions represented by the other options have different associations and implications. Choroid plexus cysts, for example, are often considered isolated findings that do not typically indicate an increased risk for chromosomal abnormalities. Amniotic band syndrome is linked to physical deformities from bands of tissue, while oligohydramnios refers to decreased amniotic fluid without direct implications for specific chromosomal syndromes like those seen with cystic hygroma. Therefore, cystic hygroma stands out as