Downs Syndrome

Using Ultrasound To Determine Down Syndrome

First and foremost, it is important for you to realize that an ultrasound cannot diagnose Down Syndrome. Why? Well, the answer to this is easy: Down Syndrome is a chromosome disorder and is impossible for ultrasound to determine any chromosomal dysfunction of any kind. The only method which can be used to confirm Down Syndrome is through a genetic test such as amniocentesis or chorionic villus sampling. So, then why this article? Although an ultrasound cannot diagnose Down Syndrome, it can be used as a tool to look for signs that there may be some Down Syndrome features. About 50% of babies which have Downs will show some symptoms on an ultrasound, and a trained sonographer should be able to pick up on these abnormalities. They would then take the necessary steps to complete other tests to confirm the presence of Downs Syndrome.

Ultrasound indicators which indicate Down Syndrome:

• An increased nuchal skin fold thickness. This is a measurement taken of the skin fold on the back of the neck.
• Heart defects.
• The “Double Bubble” sign. This indicates duodenal atresia, which is a gastrointestinal defect.
• Shortened femur and humerus measurements. These are the bones in the upper arm and the thigh.
• Hypoplasia of the middle phalanx of the fifth digit, which is a shortened bone in the middle of the pinky finger.
• The “Sandal Gap”, which is a wide space between the first and second toe.
• Pyelectasis, a dilation of the collecting system in the kidneys.
• Echogenic bowel pattern or a “bright” appearance of the bowel on ultrasound

If one or more of these ‘markers’ are seen during an ultrasound exam it does not mean that your baby definitely has Down Syndrome. What it does mean is that there is definitely an increased chance that there may be Downs in one way or another, and further testing should be carried out as soon as possible.