Helping you understand scary (but often harmless) pregnancy ultrasound findings

An ultrasound image.
Ultrasounds tell doctors about your baby’s health, but some terms on the images can be alarming without context.

Expecting parents encounter an abundance of medical terms during pregnancy. Some of these can be quite scary, particularly when the patient sees them in electronic medical records or imaging reports without context from a doctor.

Below are three fairly common ultrasound findings that you might come across. The first is a physical abnormality that, when seen by itself, almost never causes problems before or after delivery. The second and third findings are markers, which means they’re loosely associated with (but not causes of) chromosomal conditions such as trisomy 21, or Down syndrome. Alone, markers almost always are harmless. Combined with another marker or a screening test that suggests a high risk of chromosome concerns, the marker might indicate a higher risk for that condition.

These terms can sound scary. But once we have a little more information about your background and risk for congenital problems in the fetus, they rarely are cause for concern. Your doctor will probably refer you to a maternal-fetal medicine doctor for advanced imaging of the findings, just to be safe.

Single umbilical artery

Single umbilical artery ultrasound.
Single umbilical artery (SUA) appears as one small circle.

This one really freaks people out because the umbilical cord is seen as the baby’s lifeline, but this defect is common and occurs in as many as 1 percent of single-baby pregnancies and almost 5 percent of multiple pregnancies. The umbilical cord typically has three blood vessels: one umbilical vein that delivers nutrients and oxygen-rich blood to the baby and two arteries that drain blood back to the placenta. This pregnancy defect occurs when just one artery develops or one of the two arteries that did develop becomes blocked and withers away. An umbilical cord with a single umbilical artery is also called a “two vessel cord” since it contains just one artery and one vein. 

Some researchers think single umbilical artery (SUA) might be associated with slightly smaller babies or delivering a few days early. But on average, these babies weigh 6.5 pounds and arrive after 38 weeks of pregnancy – not very small or very early. Though typically harmless, the defect also carries a slightly higher risk for chromosomal conditions such as Down syndrome.

If we see this defect on an ultrasound, we’ll thoroughly examine the baby to make sure everything else is developing as expected. A single umbilical artery is associated with a higher risk that the baby might have a problem with other organ systems such as the heart and kidneys. We’ll also check the mother’s risk for chromosomal abnormalities through blood tests or other screenings. At the end of this evaluation, if a SUA is the only red flag, there’s almost never cause for concern for the baby’s health. We might do extra ultrasounds in the third trimester just to check on the baby’s growth, but nothing else needs to be done – there are no long-term complications. After delivery, there is no use for these arteries. They simply shrivel up and waste away.

Choroid plexus cyst

Choroid plexus cyst ultrasound.
Choroid plexus cyst appears as a black area within white.

As many as 2 percent of pregnancies will show choroid plexus cysts. The choroid plexus is the part of the brain that makes spinal fluid, which is released by fingerlike projections in the brain. Sometimes these get stuck together and fluid collects between them, which appears as a cyst on ultrasound.

The word “cyst” implies something that shouldn’t be there, and a cyst that has formed in the brain really sounds scary. People ask, “Is it taking up space so normal brain tissue can’t develop? Will it continue to get bigger?” But it’s really just a little fluid buildup that is seen in the middle of the pregnancy and is usually gone by about 6 months of gestation. Choroid plexus cysts on their own are not harmful. If the mother has screened positive for higher risk of the chromosome abnormality trisomy 18 in pregnancy, we would talk about additional testing. But otherwise, virtually all of these cysts go away on their own with no long-term risk and no need for follow-up testing during or after pregnancy. 

Echogenic intracardiac focus

Echogenic intracardiac focus ultrasound.
Echogenic intracardiac focus (EIF) appears as a bright white area in black.

Heart problems are the most common congenital birth defects, and it’s easy to panic when something unusual is detected on ultrasound. But echogenic intracardiac focus (EIF) is almost never something to worry about. It shows up as a bright spot on the heart in imaging, and it’s thought to be a microcalcification on the heart muscle. 

EIF occurs in as many as 5 percent of all pregnancies. It is so common in babies with Asian ethnicity that it can’t even be used as a marker. So our first question when we detect a bright spot is about the parents’ ethnic backgrounds. Similar to choroid plexus cysts, this marker might indicate a chromosomal condition if paired with other worries on the ultrasound or an increased risk for Down syndrome or trisomy 13 on a prenatal screen. Again, if it’s an isolated finding, we don’t worry about it. EIF has no impact on heart function before or after birth and almost never requires follow-up testing.

If a patient has already had an amniocentesis or chorionic villus sampling (CVS), or even a cell-free fetal DNA screen, then all of these findings are even less important.

Balancing transparency with necessity

A lot of the time, doctors don’t even mention these isolated findings if we know there’s nothing else going on with the baby and the mom is at low risk for chromosomal problems.

For most women, I mention that the finding will appear on the final ultrasound report since patients can see all of their results in our electronic medical record. I explain what it means and why they shouldn’t worry. For others, I don’t say anything at all. My patients’ emotional health is just as important as their physical health, and I don’t want them to worry unnecessarily. While I tend toward transparency, I do take it case by case. We do as much as we can to make sure you worry as little as possible, but if you do run across a term that concerns you, please ask. We’ll always give you an honest answer.

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