If you’ve been told that your growing baby has “soft markers” for Down syndrome, you likely have many concerns. What do these soft markers mean? What’s the likelihood that your child will be born with Down syndrome? And how will you know for sure?

These are common questions, and you’re not alone if you’re feeling stressed about what comes next. Let’s break down everything you need to know about soft markers for Down syndrome, what they mean, how Down syndrome is diagnosed in pregnancy, and what the outlook is for your baby and your pregnancy.

Soft markers are features that may be seen during a mid-pregnancy ultrasound — typically around 16 to 20 weeks — that may indicate an increased likelihood of fetal chromosomal abnormality.

It’s important to understand that both low risk and high risk pregnancies can have soft markers and that some soft markers may be seen in typically developing babies as well as babies who have genetic abnormalities.

Many of these soft markers either resolve or do not impact the future health of a baby. But there are associations between certain soft markers and chromosomal abnormalities such as Down syndrome.

Down syndrome is a condition in which a fetus is born with an extra copy of chromosome 21 (trisomy 21). Babies born with Down syndrome may have intellectual disabilities, low muscle tone, and a distinctive facial appearance. Fifty percent of people with Down syndrome have heart defects, as well.

The condition is the most frequent hereditary cause of intellectual disability. It affects about 1 in every 700 babies and is more common in babies born to people ages 35 or older at the time of conception.

Children with Down syndrome can live happy and full lives with proper medical care and family support.

Soft markers for Down syndrome are specific sonographic features that are more often seen in fetuses with Down syndrome. Soft markers for Down syndrome are typically seen during second-trimester ultrasounds.

Having these markers doesn’t necessarily mean your baby has Down syndrome, but approximately 30% of babies with Down syndrome have these markers on their mid-pregnancy ultrasound.

Soft markers for Down syndrome may include any of the following:

  • enlarged brain ventricles (ventriculomegaly)
  • smaller-than-normal or absent nasal bone
  • increased thickness of the nuchal fold
  • small, bright point on the heart (intracardiac hyperechogenic focus)
  • abnormality of the aortic arch (aberrant right subclavian artery, or ARSA)
  • bowel that appears white on ultrasound (hyperechogenic bowel)
  • mild kidney swelling (hydronephrosis)
  • shortening of the humerus or femur bones

Ultrasounds are a type of prenatal screening test, meaning that these tests can tell you whether there’s an increased chance your baby may have Down syndrome. However, they cannot confirm that your baby has it.

To get a definite diagnosis, you would need a prenatal genetic diagnostic test to confirm. These tests require that a sample of your baby’s genetic material be obtained for testing. Samples are examined for extra genetic material from chromosome 21.

Diagnostic tests are more invasive than screening tests, and may slightly increase your chances of complications, such as miscarriage. Tests used to confirm a Down syndrome diagnosis include:

Sometimes Down syndrome isn’t diagnosed until your baby is born. In this case, your baby may be diagnosed based on certain symptoms, such as:

  • low muscle tone (hypotonia)
  • shorter-than-usual neck
  • extra flesh on the back of the neck (nuchal folds)
  • facial appearance and nose looks flattened
  • smaller-than-average head (microcephaly), ears, mouth
  • eyes that slant upward (epicanthal folds)
  • short, wide hands and fingers
  • reduced attention span
  • developmental delays

While all soft markers for Down syndrome may increase the likelihood that your child has Down syndrome, some markers are more predictive than others.

A 2013 meta-analysis on soft markers and Down syndrome found that most of the time, when a fetus had only a single soft marker, the risk of that fetus having Down syndrome was only slightly increased.

The researchers examined 48 studies on soft markers and Down syndrome diagnosis. They found that having certain markers provided a more elevated risk than others. These included:

  • enlarged brain ventricles
  • increased thickness of the nuchal fold (skin on the back of the neck)
  • abnormal arteries
  • small or absent nasal bone

The study researchers found that a finding of enlarged brain ventricles, increased thickness of nuchal fold, and abnormal arteries increased the likelihood of a Down syndrome diagnosis by 3–4 fold and that a small or absent nasal bone increased the chances by 6–7 fold.

Again, it’s important to keep in mind that soft markers are not definitive — they’re part of screening tests only. To confirm a diagnosis of Down syndrome, you’d need to have a diagnostic test performed, such as amniocentesis or chorionic villus sampling.

Consider discussing the pros and cons of these options with your OB-GYN, midwife, or genetic counselor.

How common are soft markers?

Studies have estimated that almost 6% of fetuses will have a soft marker found on their second-trimester ultrasound. In other words, about 6 in every 100 expectant parents will be told that their fetus has a soft marker.

What is your risk of Down syndrome if no soft markers are found?

If no soft markers linked to Down syndrome are found during your second-trimester ultrasound, the risk that your baby will be diagnosed with Down syndrome is very low. In fact, your risk decreases about 7.7 fold.

What other Down syndrome screening tests are available during pregnancy?

Second-trimester ultrasounds aren’t the only screening tests available for Down syndrome. Other possible screening tests include various blood tests, a nuchal translucency test, additional ultrasounds, and various integrated screening tests.

It can be concerning if you’re told that your baby has a soft marker for Down syndrome. But soft markers are more common than you might think, and most of the time, they do not mean a baby has Down syndrome.

Every pregnancy is different, so it’s best to consult with your healthcare team so they can explain what these findings mean for your pregnancy and your baby.