Down Syndrome

[Anonymous]

All the posts about soft markers during the 20 week ultrasound made me wonder . . .

1) What percentage of children born with Down Syndrome had signs of soft markers at the 20 week ultrasound?

2) I only started noticing posts about soft markers within the last year. Is this something new? Do all major radiology practices screen for these soft markers?

My husband and I decided not to perform NT, Amnio, or CVS. I do not regret our decision, but I was just wondering what the likelihood is of them actually giving a probable diagnosis of DS at the 20 week ultrasound.

[Anonymous]

Actually, pretty good, I think. I was well into my 40's when DD was born but we did not do any pre-testing either. It's amazing what they can tell from that 20 week ultrasound. We got a very confident "all's well" at that point.

[Anonymous]

Prenatal screenings only estimate the chance of the fetus having Down syndrome. Like all estimates, they can be really off, or not. My DD had some soft markers but she turned out not to have Down Syndrome. Same with my niece. Same with one of my friend's daughters.

The only way to know for sure prenatal is anmio or CVS.

[Anonymous]

OP here, although a bit old, I found this article answered several of my questions:

http://www.medscape.com/viewarticle/408862_1

Identifying Ultrasound Markers for Down Syndrome


from Medscape General Medicine™
Posted 06/13/1997
Dibe Martin, MD, Michael O. Gardner, MD, MPH, Valerie J. Rappaport, MD, University of New Mexico Health Sciences Center

Here is the Index:
Abstract and Introduction
First-Trimester Ultrasound
Second-Trimester Ultrasound
Trisomy 21: Major Malformations And Screening Indicators
Major Malformations
Screening Indicators: Gestational Age 16 to 18 Weeks
Conclusion: Evaluating the Usefulness of Ultrasound

Abstract and Introduction
Abstract
Although the incidence of Down syndrome increases with advancing maternal age, the use of maternal age alone as a screening tool results in the identification of only about one third of the cases of fetal Down syndrome. Screening tools for Down syndrome (trisomy 21) have become more sensitive and specific during the last few years. The use of biochemical markers for the screening of patients with fetuses having chromosomal anomalies has become more widespread in the obstetric community. The triple-screen test uses maternal age plus serum alpha-fetoprotein, unconjugated estriol, and human chorionic gonadotropin levels to calculate a risk for fetal Down syndrome. Because as many as 11% to 35% of fetuses with chromosomal defects have anatomical characteristics that can be visualized on a detailed ultrasound evaluation, researchers are studying the usefulness of this imaging technique as a screening tool for Down syndrome. Ultrasound findings associated with trisomy 21 may be divided into 2 groups. The first group comprises the common major malformations associated with Down syndrome, such as duodenal atresia and cardiac disease. The second group comprises the ultrasound screening indicators, that is, anatomical malformations highly specific to Down syndrome. This group includes brachycephaly, mild ventriculomegaly, macroglossia, abnormal facies, nuchal edema, echogenic or hyperechoic bowel, pyelectasis, and shortening of the limbs. Although the diagnosis of chromosomal anomalies remains dependent on karyotyping, the use of ultrasound may limit the number of invasive procedures and allow for more accurate genetic counseling of the mother at risk for delivering an infant with Down syndrome.

Introduction
Down syndrome (trisomy 21) occurs when the genetic material contains an extra copy of chromosome 21. The overall incidence in the general population of this abnormality is approximately 1 in 800 live births. The likelihood of having a child with Down syndrome increases with maternal age; however, because a larger portion of the pregnant population is under 35 years of age at delivery, the great majority of Down syndrome infants are born to women under age 35 years. Down syndrome is distinguished by a variable range of medical complications as well as characteristic physical abnormalities, postnatal growth delay, and mental retardation.
Although it is known that the incidence of Down syndrome increases with advancing maternal age, the use of maternal age alone as a screening tool identifies only about one third of Down syndrome cases. Screening tools for its detection have become more sensitive and specific during the last few years, and the use of biochemical markers to detect fetal chromosomal abnormalities has become more widespread in the obstetric community. The triple-screen test uses maternal age plus maternal serum alpha-fetoprotein, unconjugated estriol, and human chorionic gonadotropin levels to calculate the risk for fetal Down syndrome. Numerous studies have reported that the triple-screen test may detect 60% of fetal Down syndrome cases in women younger than 35 years of age.

In an effort to improve the sensitivity and specificity of screening for Down syndrome, many have turned to ultrasound. Some fetuses with chromosomal defects (11% to 35%) have identifiable external or internal anatomical characteristics that can be seen on a detailed ultrasound evaluation. Knowing this, researchers have tried to identify characteristics found on ultrasound examination that could be used as markers to screen for chromosomal anomalies.

This article focuses on ultrasound markers associated with the diagnosis of Down syndrome. It is important to emphasize that although these markers may aid in the diagnosis of this syndrome, the definitive diagnosis may only be reached by karyotyping after amniocentesis, chorionic villi sampling (CVS), or percutaneous umbilical blood sampling (PUBS).

You'll have to go to the website to get the rest of the article.