Isolated soft markers do not increase age-related risk

[secondround]

Found this article - it basically says that soft markers (except thickened nuchal fold) do not increase the risk of Down Syndrome in a low-risk population. It explains that in their study, 90% of babies with trisomy 21 and a hard marker also had a soft marker, hence the high statistics connected with soft markers. The soft markers on their own, however, did not increase a woman's risk at all, really (and the absence did not really decrease it that much). Apparently most studies were done retrospectively, whereas this one was actually a prospective study conducted to test the effectiveness of the "genetic sonogram." All the women in the study were considered high-risk based on serum testing.

Prenatal Diagnosis, Volume 27 Issue 6, 19 Mar 2007
http://www3.interscience.wiley.com/journal/114189419/abstract

Second trimester prenatal ultrasound for the detection of pregnancies at increased risk of Down syndrome
Rebecca Smith-Bindman 1 2 3 *, Philip Chu 1, James D. Goldberg 4

RESULTS:
Overall 9244 women with singleton pregnancies were included, including 245 whose fetuses had Down syndrome. Overall, 15.3% of the women had an abnormal genetic sonogram, including 14.2% of pregnancies with normal fetuses and 53.1% of those with Down syndrome. If the genetic sonogram were normal, the risk that a woman had a fetus with Down syndrome was reduced (likelihood ratio 0.55 [95% CI 0.49, 0.62]) However, if the normal genetic sonogram were used to counsel these high-risk women that they could avoid amniocentesis, approximately half of the cases of Down syndrome (115 of 245) would have been missed. The isolated ultrasound soft markers were the most commonly observed abnormality. These were seen in a high proportion of Down syndrome fetuses (13.9%) and normal fetuses (9.3%). In the absence of a structural anomaly, the isolated ultrasound soft markers of choroid plexus cyst, echogenic bowel, renal pyelectasis, clenched hands, clinodactyly, two-vessel umbilical cord, short femur, and short humerus were not associated with Down syndrome. Nuchal fold thickening was a notable exception, as a thick nuchal fold raised the risk of Down syndrome even when it was seen without an associated structural anomaly.