If you were told that there were "soft markers" for Down syndrome during your level 2 ultrasound, you may be wondering what it means.
A soft marker may indicate an increased likelihood of a chromosomal abnormality — but it's simply not very reliable, especially considered outside of the bigger picture. Some soft markers have a higher association with Down syndrome than others. Many are spotted in fetuses without any genetic abnormalities and resolve before birth. And none are 100 percent proof-positive; they simply turn up statistically more often in babies who have Down syndrome than in those who don't.
In fact, these markers are spotted on as many as 11 to 17 percent of all babies. Each needs to be interpreted in the context of other screenings, structural anomalies and risk factors. So talk to your practitioner about the particular markers your ultrasound picked up.
Here are common soft markers that show up in the second-trimester ultrasound:
- Echogenic intraventricular focus (EIF), a small bright spot on the baby’s heart that could come from calcium deposits
- Echogenic bowel, which means the bowel area appears brighter than normal
- Choroid plexus cysts (CPC), a fluid-filled space in the brain which appears as a cyst and is not considered a brain abnormality, which is more commonly associated with trisomy 18
- Renal pyelectasis, which means the main area of a kidney is enlarged
- Short femur and/or humerus, or the length of the thigh or arm bones is smaller than normal
- Mild cerebral ventriculomegaly, cerebral spinal fluid (CSF) is trapped in the brain’s ventricles, causing them to dilate and grow abnormally large
- Absent or shortened nasal bone, this marker has a stronger link with Down Syndrome than most others
One soft marker that might have shown up on the first-trimester NT screening (which is always performed between weeks 10 and 13) is nuchal-fold thickening, where the area at the back of a baby’s neck accumulates fluid, causing it to appear thicker than usual. This soft marker has a higher correlation to Down syndrome than any other. Because it's also associated with fetal heart defects, your practitioner may have suggested a fetal echocardiogram at around 20 weeks to screen for heart defects if your baby's measurements were high.
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If your practitioner spots a soft marker, they will likely offer the option of amniocentesis, which would need to happen between 15 and 20 weeks. The test will be able to tell you with more than 99 percent accuracy whether your child has Down syndrome or another chromosomal abnormality. However, for patients who have had normal results from non-invasive prenatal testing (NIPT), which can be performed anytime after week 9, there would likely be no further testing recommended, as the predictive values for NIPT are typically better than the soft markers with regards to Down’s syndrome.
Whether or not you want further testing, however, is up to you. But keeping tabs on your baby’s growth can be a good thing — and knowledge is power. While technology can lead to extra worry for some parents, for many others, knowing what comes next can make for a much less stressful pregnancy.
In the meantime, here are some steps to take:
- Talk to a genetic counselor. Make an appointment to sit down with your practitioner's genetic counselor (if there isn't one, ask for a lengthier sit-down with your regular doctor). A genetic counselor can assess your chances of having a child with Down syndrome more accurately, taking into account all of your prenatal test results, your age and other risk factors, as well as talk to you about further tests.
- Do what feels right. Definitely talk out the issue with your doctor — and family and friends (if you like) — but in the end, make the decision that feels best for you and your partner if you have one. There are no right answers when it comes to prenatal testing. Your best friend may say, “Oh, I would have to know!” but you may not feel the same. And that’s okay.
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