A 30-year-old G1P0 at 8 weeks’ gestation presents for her first prenatal visit. She has no significant past medical or surgical history. A 29-year-old friend of hers just had a baby with Down syndrome and she is concerned about her risk of having a baby with the same problem. The patient reports no family history of genetic disorders or birth defects.
You offer her a first trimester ultrasound looking for ultrasound markers associated with Down syndrome.
Which of the following ultrasound markers is most closely associated with Down syndrome?
A. Choriod plexus cystAll of the markers listed are associated in some degree with Down syndrome as well as other genetic abnormalities, but increased NT is most closely and consistently associated. Increased NT is an early presenting feature of Down syndrome. Guidelines for systemic measurement of NT are standardized. Specific training and ongoing audits of examination quality are required for screening programs in order to ensure the expected detection rate. The optimal time to schedule NT measurement is between 12 and 13 weeks, but results are considered valid between 10 4/7 and 13 6/7 weeks. This results in Down syndrome detection rates of 72% at a screen positive rate of 5%. Most centers use a thickness of >/= 3 mm to define abnormal.