Soft Markers

Many parents look forward to their 18-20 week anatomy ultrasound (click for more information on the anatomy scan), only to discover that the doctor sees a ‘soft marker’. Soft markers are not abnormalities within the baby but are normal anatomical variants. In the quest to find fetuses that have Down’s Syndrome or other serious abnormalities, anything that was seen to be out of the ordinary has been greatly studied to see if there is a possible correlation between the variant and abnormal outcomes. Sure enough, there have been associations, albeit weak, between ‘soft markers’ and babies with Down’s or other problems. But before you panic, understand that even if you are told your baby has a soft marker, the chances are more than excellent that everything is fine. In fact, 10-15% of all babies have at least one soft marker. Most of the time, the finding of a soft marker in an otherwise normal-appearing baby is a big to-do about nothing. Years ago, doctors were more interested and wary when soft markers were found, but over time, it became clear that the most common problem associated with soft markers is unnecessarily scaring the wits out of parents. Much less emphasis is placed on soft markers now that we have more trusted, reliable screening methods such as First Trimester Screening and NT Ultrasound (click for more information).

The bottom line is that generally, in an otherwise low risk pregnancy with a normal first trimester screening test, the presence of a soft marker or two does not significantly increase the odds that your baby has a problem and more invasive testing with amniocentesis is not usually warranted. If you are already high risk such as being over 35 or the baby has other anatomical abnormalities, your doctor or a midwife will advise you as to whether or not amniocentesis is an appropriate next step.

What are soft markers?

Again, soft markers are not abnormalities but are anatomical variants. For example, an anatomical ‘variant’ is having naturally red hair—most people aren’t born redheads, but having red hair does not mean you are physically abnormal. It’s just the way you are built. Same goes for ‘soft markers’, most fetuses don’t have them, but if they do, most of the time they are not physically significant. But, in rare cases, they can be a clue that a larger problem exists.

The following is a list of some Soft markers:

  • Choroid plexus cysts: These are rounded cystic structures seen in the part of the brain that makes the cerebral-spinal fluid. Cysts in the brain sound scary, but they have no significance to the development and intelligence of your baby. They are significant in that 30% of babies with Trisomy 18 have them, but keep in mind, very few babies with choroid plexus cysts have Trisomy 18!
  • Borderline ventriculomegaly: In the brain, the lateral ventricle is a structure which holds some of the cerebrospinal fluid. It is routinely measured on every anatomy scan to look for hydrocephalus or ‘water-on-the-brain”. If it is prominent, meaning it is at the very upper range of normal, it can be associated with a host of problems. It is more common and more likely to be normal in boys than girls. If this is found, your doctor will likely do some additional testing and follow ups just to make sure it doesn’t represent a problem or worsen.
  • Echogenic intracardiac focus: Fancy words for a ‘bright spot’ in the heart which represents some calcifications or prominence to the papillary muscle. This doesn’t affect the function of the muscle or the beating of the heart. It’s seen in approximately 20% of all Down’s Syndrome fetuses. This is a relatively common finding on ultrasound, approximately 5% of all fetuses have this. Yet only approximately .25% of fetuses have Down’s Syndrome. Incidentally, it is more commonly found in Asian mothers than others, and is much more likely to be normal than indicative of Down’s.
  • Echogenic Bowel: Sometimes there can be very bright spots seen within the baby’s abdomen or liver. Most of the time, this represents nothing but in some cases, it can be caused by Down’s Syndrome, cytomegalovirus (CMV), or cystic fibrosis. A few normal babies with echogenic bowel will show poor growth later in the pregnancy so your doctor might order follow up ultrasounds in the later 2nd and 3rd trimesters to follow growth.
  • Single umbilical artery: Most babies are born with an umbilical cord that contains 2 arteries and one vein. Normal cords are known as 3 vessel cords. Sometimes, there is only one artery and one vein. Again, most of the time, this is just a curiosity and the baby is born healthy and well. However, in some cases, 2 vessel cords can be associated with kidney or heart abnormalities and/or poor growth. A careful look at the anatomy will be performed to rule out any associated defects.  Additional ultrasounds will likely be done to follow the growth.
  • Mild pyelectasis: This occurs when there is fluid within the part of the kidney that collects urine. A little bit of fluid (less than 4 mm.) is perfectly normal. More than that has been loosely correlated with Down’s Syndrome. Even if Down’s Syndrome is not suspected, chances are you will have follow up ultrasounds to keep track of the amount of fluid. In some cases, the amount of the fluid can increase and signal a urinary blockage or other problem with the kidney and bladder. Again, these follow ups can be nerve-wracking but most of the time, even if the kidneys continue to retain fluid, it can be medically managed and successfully treated after the baby is born.

Should you find yourself in the position of being told your baby has any of these issues, try not to assume the worst. Your doctor or midwife is obliged to tell you of the findings and the risks, which can sometimes sound horrible. How alarmed you get is often a function of the personality of your doctor or midwife. Some will emphasize all the worst case scenarios since there are no guarantees in medicine (OR parenting, for that matter). Despite being told that something might be wrong, believe them if they say they your risks are low and they are not concerned.



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