Turner Syndrome: This condition is most commonly associated with septated cystic hygroma in the first trimester. The presence of a septated cystic hygroma significantly increases the risk for Turner Syndrome, which is characterized by monosomy X (45,X) and affects female fetuses.

Trisomy 21 (Down Syndrome): While less commonly associated with septated cystic hygroma compared to Turner Syndrome, Trisomy 21 is still a significant consideration due to its overall higher incidence in the population. The presence of a septated cystic hygroma increases the risk for Down Syndrome, among other chromosomal abnormalities.
Trisomy 18 (Edwards Syndrome): This chromosomal abnormality can also present with increased nuchal translucency and cystic hygroma, although it is less common than Trisomy 21.
Trisomy 13 (Patau Syndrome): Similar to Trisomy 18, Trisomy 13 can be associated with increased nuchal translucency and cystic hygroma, though it is less frequent.

Noonan Syndrome: A genetic disorder that can present with cystic hygroma and increased nuchal translucency. It's crucial to consider this diagnosis due to its implications for fetal and neonatal management, even though it's less common than chromosomal abnormalities.
Other Chromosomal Abnormalities: Various other chromosomal abnormalities, such as deletions, duplications, or mosaicism, can also present with septated cystic hygroma. Identifying these conditions is critical for providing accurate genetic counseling and prenatal care.

Aicardi Syndrome: A rare genetic disorder that primarily affects females, characterized by agenesis of the corpus callosum, retinal abnormalities, and seizures. While rare, it can be associated with increased nuchal translucency and cystic hygroma.
Other Rare Genetic Syndromes: There are numerous rare genetic syndromes that can present with features including cystic hygroma. These are often diagnosed through a combination of clinical findings, family history, and genetic testing.