Soft Markers
A soft marker is something your healthcare provider might see during a routine pregnancy ultrasound exam. If a soft marker is found but the fetus is otherwise healthy, it is likely a normal finding. However, if other risk factors are present, finding a soft marker can mean that the fetus has an increased risk of a genetic disorder known as aneuploidy.
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Aneuploidy is a genetic disorder where there are missing or extra chromosomes. The most common aneuploidy is Down syndrome. Instead of the normal two copies of chromosome 21, there is an extra copy. Having an extra chromosome is called trisomy. Other common aneuploidies include trisomy 13 and trisomy 18. Prenatal testing for these disorders is offered to all pregnant people.
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Two different types of tests are available to detect certain genetic disorders, including aneuploidy: prenatal genetic screening tests and prenatal genetic diagnostic tests.
Prenatal genetic screening tests can tell you if the fetus has a higher risk of having a genetic disorder. A blood test called cell-free (cf) DNA screening (also called noninvasive prenatal testing, or NIPT) can be done starting at 10 weeks of pregnancy. This test looks for chromosome abnormalities in small fragments of genetic material (DNA) in your blood, many of which come from the placenta. The cfDNA test can assess the risk of Down syndrome, trisomy 13, trisomy 18, and some sex chromosome disorders in the fetus. There are also other blood tests that measure the amount of certain substances in your blood to assess the risk of aneuploidy, but these tests are not as commonly performed as cfDNA.
cfDNA test results are reported as “low-risk” or “high-risk.” A low-risk cfDNA result means the chance of the fetus having an aneuploidy is very low. However, there is still a small chance that the fetus could be affected. A high-risk result means that the chance of the fetus having an aneuploidy is higher. However, more testing is needed to know with certainty whether the fetus is affected. These include a detailed ultrasound exam or diagnostic testing with amniocentesis or chorionic villus sampling.
Prenatal genetic diagnostic testing is the most accurate way to find out whether the fetus has an aneuploidy. Diagnostic testing is offered to all pregnant people as a first genetic test (instead of a screening test), regardless of age or risk factors.
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The following risk factors have been linked to an increased risk of aneuploidy:
Maternal age (usually older than age 35)
Results of first or second-trimester genetic screening tests that show a high risk for aneuploidy
First or second-trimester ultrasound exam findings linked to a high risk for aneuploidy
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Most soft markers are found during the second-trimester ultrasound exam, sometimes called the “anatomy scan.” This exam is done between 18 and 22 weeks of pregnancy to check the development of the fetal organs and body parts. Some structural anomalies can be found during this exam.
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Common soft markers found on an ultrasound are listed in the table below.
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If a soft marker is found on the routine anatomy scan, you will be offered a detailed ultrasound exam to check whether the marker is isolated. An isolated soft marker occurs in the absence of another anomaly, poor fetal growth, or any other soft marker. If the exam confirms that the soft marker is isolated, the next steps depend on your cfDNA test results. If your cfDNA test result is low-risk, additional testing is usually not recommended. If you haven’t had a cfDNA test, genetic counseling to assess your genetic risk factors and genetic testing may be offered.
You have a choice in deciding whether to have a detailed ultrasound exam. SMFM recommends discussing this exam with your healthcare provider so that you can make an informed decision.
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Diagnostic testing with amniocentesis may be offered depending on the type of soft marker, your prior
cfDNA test results and detailed ultrasound exam results, and the health of your pregnancy. An amniocentesis can tell with a high degree of accuracy whether the fetus has an aneuploidy. It can also find other genetic disorders that you and your healthcare provider can request.
Your preferences and beliefs about what you would do if amniocentesis results show a disorder play a role in whether you want to have this testing. Your healthcare provider can explain what is known about the soft marker, review your risk factors, and discuss all of your options to help you and your family make an informed decision.
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Some isolated soft markers are linked to pregnancy problems unrelated to aneuploidy. For this reason, your healthcare provider may recommend extra tests and imaging for some soft markers. The table explains the recommended tests and why they might be needed.
Types of Soft Markers
| Illustration | Soft marker | Description | Extra care needed during pregnancy |
|---|---|---|---|
 | Echogenic intracardiac focus (EIF) | A small area in the heart that appears as bright as bone | None |
 | Echogenic bowel | A brighter-than-normal area in the digestive tract | This marker has been linked to cystic fibrosis, poor fetal growth, cytomegalovirus infection (CMV), and bleeding. Depending on your medical history, an ultrasound exam to check fetal growth in the third trimester, genetic testing for cystic fibrosis, and tests for CMV infection may be recommended. |
 | Choroid plexus cyst (CPC) | A small area of fluid in the part of the brain called the choroid plexus. | None |
 | Single umbilical artery (SUA) | An umbilical cord that has only 1 instead of the normal 2 arteries | The risk of low birth weight (fetal growth restriction) can be higher in fetuses with an SUA. Growth evaluation is recommended in the third trimester. |
 | Urinary tract dilatation (UTD) | Enlargement of an area of the kidney | A repeat ultrasound in the third trimester may be recommended to check the kidneys. |
 | Shortened humerus, femur, or both | Shortened bones of the upper arm or thigh | When found in the second trimester, a repeat ultrasound in the third trimester is recommended to check fetal growth and limbs. |
 | Thickened nuchal fold | Thickened skin of the fetal neck; can also be detected during the first trimester | None |
 | Absent or hypoplastic nasal bone | The nasal bone is absent or smaller than expected | None |
Quick Facts
A soft marker is a minor finding seen during a pregnancy ultrasound exam.
A soft marker is usually a variation of normal fetal development. But when other risk factors are present or there is more than 1 soft marker, it can mean that the fetus is at increased risk of a genetic disorder known as aneuploidy (an abnormal number of chromosomes).
A detailed ultrasound exam is offered if a soft marker is found.
If the detailed ultrasound exam confirms that the soft marker is isolated, and you have had a low-risk prenatal screening test (eg, cell-free DNA test) result, you can be reassured that the chance of aneuploidy in the fetus is very low. No other genetic testing is needed in this case.
Some isolated soft markers are linked to pregnancy problems unrelated to aneuploidy. For this reason, your healthcare provider may recommend extra tests and imaging for some soft markers.
If the soft marker is not isolated or if there are other risk factors for aneuploidy, an amniocentesis may be offered depending on the type of soft marker, your prior cell-free DNA test and detailed ultrasound exam results, and the health of your pregnancy.
Glossary
Amniocentesis: A procedure in which a sample of amniotic fluid is removed from the uterus during pregnancy and tested to look for genetic problems in the fetus.
Anatomy Scan: A routine ultrasound exam done between 18 and 22 weeks of pregnancy to check the development of the fetus’s body parts and organs.
Aneuploidy: A genetic disorder in which there are missing or extra chromosomes.
Cell-free (cf) DNA Screening Test: A prenatal screening test that looks for certain chromosomal disorders in the fetus. It uses small pieces of DNA (genetic material) from the placenta that circulate in the blood of a pregnant person. Also called noninvasive prenatal testing (NIPT).
Chorionic Villus Sampling (CVS): A procedure in which a small sample of the villi, a part of the placenta, is removed and tested to look for genetic problems in the fetus.
Chromosomes: The structures inside cells that carry genes, the pieces of hereditary material passed down from parents to offspring.
Cystic Fibrosis: An inherited disorder caused by the production of thick, sticky mucus, which can build up in organs such as the lungs and pancreas and lead to damage, blockages, and infections. It is the result of a gene passed down in families.
Cytomegalovirus (CMV): A virus that can be passed from a pregnant person to the developing fetus. Babies born with CMV can have problems such as jaundice, an enlarged liver and spleen, and a skin rash. Babies without symptoms at birth can develop deafness, cognitive difficulties, eye problems, and seizures.
Detailed Ultrasound Exam: An ultrasound exam that provides a comprehensive assessment of fetal body parts and organs.
Fetus: The stage of development during pregnancy from 9 weeks to birth.
Genetic Disorder: Any disorder caused by a genetic change, an abnormal number or structure of chromosomes, or a combination of genetic and other factors.
Noninvasive Prenatal Testing (NIPT): Prenatal blood tests that measure certain substances in the mother’s blood or analyze fragments of placental DNA to screen for aneuploidy.
Prenatal Genetic Diagnostic Tests: Tests done during pregnancy that determine with a high degree of accuracy whether a genetic disease or disorder is present in the fetus.
Prenatal Genetic Screening Tests: Tests done during pregnancy that assess the chance that a genetic disorder is present in the fetus.
Sex Chromosome Disorder: A genetic disorder in which there is an abnormal number or structure of the sex chromosomes.
Sickle Cell Disease: An inherited disorder that causes blood cells to become crescent (sickle)-shaped, making it difficult for them to pass through small blood vessels.
Soft Marker: A finding on ultrasound that is usually a normal variation but can be associated with a chromosome disorder.
Trimester: The three-month periods in which pregnancy is divided. The first trimester is months 1 to 3 (weeks 1 to 12); second trimester is months 4 to 6 (weeks 13 to 27); and the third trimester is months 7 to 9 (weeks 28 to 40).
Ultrasound: Use of sound waves to create images of internal organs or the fetus during pregnancy.
Last Updated: November 2023