A minor (or soft) marker is a difference that is seen on ultrasound that does not cause any health concerns itself, but increases the chance for certain underlying health conditions. Most of the time, a minor marker is a slight variation in development that is not linked to an underlying health issue.
For example, shorter than average femur (thigh) bones are considered a minor marker that increases the chance for Down syndrome. This is because many babies with Down syndrome have shorter than average thigh bones. But there are also many babies who do NOT have Down syndrome but DO have shorter than average thigh bones. There are also some babies with Down syndrome that have average thigh bones. If a minor marker is found on your ultrasound, it is important to talk with your doctor and/or genetic counselor to understand what that marker means for your pregnancy.
You should be talk with a medical professional that can provide you more information about what these findings may mean for your baby. Depending on what marker(s) is seen, your doctor may offer you a screening test, such as cell-free DNA, or a diagnostic testing, such as amniocentesis, to look for certain genetic and chromosomal conditions like Down syndrome. It is always a personal choice whether or not to undergo any prenatal testing.
Depending on the markers that are seen on the ultrasound, it may be recommended that you have a follow-up specialized ultrasound to more carefully evaluate the baby’s heart, called a fetal echocardiogram. Babies with chromosome conditions including Down syndrome have a higher chance for a heart defect. If an ultrasound increases the chance for the pregnancy to have a chromosome condition, it may be important in planning your delivery to determine if the baby is likely to have a heart defect.
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