Soft Markers for Down Syndrome

Soft markers are signs that a fetus may have a chance of having Down syndrome. They can also show a higher risk for other abnormal chromosomes. The risk factors include older age of mothers (over 35), appearance of soft markers for Down syndrome on ultrasound, and blood tests that show elevated levels of proteins seen in pregnancies with a chromosome abnormality. This article will help you understand more about the soft markers and what they mean.

What Are Soft Markers for Down Syndrome?

Soft markers are slight indicators that there may be an elevated chance of Down syndrome in the fetus. There are two kinds of markers: Hard and Soft. Soft markers are not completely 100% positive and may only be a small chance that the abnormality has occurred. On the other hand, hard markers are a stronger chance of Down syndrome, but for the purpose of this article we will only focus on “soft markers.”

For a soft marker to be of significance, there needs to be other risk factors present such asolder maternal age over 35, family history of chromosome disorders, and abnormal proteins on blood testing. The doctor will merely use soft markers as part of many diagnostic tools.

How Do They Find Soft Markers?

Soft markers for Down syndrome are found on ultrasound scans done during the second trimester of pregnancy. Most doctors do an ultrasound early in the second trimester between 16 and 20 weeks. Keep in mind that an ultrasound done around the 20th week often has signs of soft markers, or around 1 in 30. This doesn’t mean the baby has Down syndrome, but certain soft markers may mean there is an elevated risk.

Here are some of the common soft markers:

  • Thickened nuchal pad – A thickened nuchal pad is a thickening of the fetal skin on the backside of the neck. This is not to be confused with nuchal translucency that is a pocket of fluid inside this skin pad.
  • Echogenicity of the bowel – A bright white color inside the bowel on ultrasound is known as an “echogenic bowel.” This does not necessarily mean there is Down syndrome, but shows an increased risk. An echogenic bowel can be an indication of other conditions.
  • Shortened long bones – The femur and the humerus are long bones in the body. If they appear shortened, this could be an indication of Down syndrome. These bones do tend to grow at different rates, so if they appear shortened on one ultrasound the doctor will compare measurements between a few ultrasounds and compare them.
  • Echogenicity of the heart – A bright white color can appear inside the heart. These tend to appear in “spots” and may be an increased indication of Down syndrome.
  • Renal pelvis dilation – It is completely normal for the fetal kidney to make urine during pregnancy. This urine sits in the renal pelvis, which is also the center of the kidney. There is usually only a minute amount (5mm) and if there is more fluid, this is called “renal pelvis dilation.” This isn’t a cause for concern, but if found will be monitored in additional ultrasounds to make sure it’s not one soft markers for Down syndrome that will actually end up as the condition.
  • Choroid plexus cyst – A choroid plexus cyst develops inside the tiny blood vessels in the baby’s brain. These usually go away by the 28th week, but can signal a chromosome defect.
  • Hypoplastic nasal bone – During pregnancy the nasal bone in the fetus grows along with the other bones. A hypoplastic nasal bone is one that shows up smaller with slow growth on ultrasound evaluations. This marker is still considered a soft marker for Down syndrome, but is evolving as one of the hard markers because of the increased presence in Down syndrome cases.
  • Only one umbilical artery – This condition is actually quite common, even in normal pregnancy. It affects around 1 in 100 pregnancies and usually has no clinical significance nor do doctors really understand why it happens. It tends to happen more often in twin or triplet pregnancies, but can sometimes be a soft marker for chromosome abnormalities.

What Should Parents Do If Soft Markers for Down Syndrome Are Found?

The comforting news is that many ultrasounds have abnormalities show up that could be soft markers and the baby is born normal and healthy. In cases where the soft markers are an indication for Down syndrome, the parents have a choice on whether to continue the pregnancy, decide on treatment options if the baby has congenital defects, and/or plan for future care of the child. This is why ultrasound screenings are done early in the second trimester to allow for time to make these decisions.

Experiences of Other Moms

“When I was 19 weeks, they did my second trimester ultrasound. They found four soft markers; a lemon shaped head, two choroid plexus cysts, and some echogenic foci. They sent me to a perinatologist for a special level II ultrasound. The doctor came in after the ultrasound and said there were more details on the special ultrasound and things didn’t look too good. There were also some things on the baby’s heart that may be congenital heart defects. They told me I would need an amniocentesis to confirm any issues.

“I just wantto let you know that sometimes soft markers for Down syndrome may not show up on ultrasound. My baby was born early at 34 weeks. He weighed 4 pounds and was positive for Down syndrome at birth. All of my testing, blood markers, and ultrasounds were normal. It was such a shock to me because I thought everything was fine. The doctors explained to me that soft markers are called soft markers because they are not always positive or negative for Down syndrome. They also told me there is no way to completely diagnose the disorder prior to birth, just sometimes a suspicion but you can’t be sure until you see the baby.”

They did the amnio that week and then had me go for a fetal echocardiogram. We had to wait a few weeks for all the results to come back. We were so very nervous for our little baby. During this time, the doctors reviewed all the reports and did new measurements. They actually found the ultrasound results were normal when they compared them to others. Still, we waited on the amnio and echo results. Exactly two weeks after the tests, we received the results and everything came back normal and fine. We went on to have a very healthy son with no health issues at all. I hope this can help other moms feel comfort when they are worried.” 

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