Emily Oster

4 min Read Emily Oster

Emily Oster

Are Ultrasounds Safe?

Q&A on risks and benefits

Emily Oster

4 min Read

Have you done any research into the safety of ultrasounds (both scans and their use to monitor how things are going during labour)?

I’ve read that animal studies on ultrasounds indicate they might not be as safe as we seem to think they are, especially given the higher-powered ultrasound machines that are in use these days (and the potential incompetence of ultrasound operators). I also understand that there is some association between ultrasounds and left-handedness.

I’m keen to understand the risks vs. benefits of getting ultrasounds done and what the possibility of any harm is compared with any benefits one might obtain (i.e. does the science actually show that ultrasounds result in better outcomes, and how does this compare with what the literature says about safety)?

I’m currently 17 weeks and will need to make a decision soon about whether to get an anatomy scan, so would be really interested in your thoughts on this. Thanks!

—First-Time Mum

I want to answer your question in the reverse order: benefits and then whether the discussion of risks has merit.

The benefit of ultrasounds is in detecting possible health concerns with your baby. The 20-week anatomy scan you refer to, for example, is a detailed look at your baby’s organs. It can identify heart conditions, intestinal blockages, problems with kidney development, etc. I want to be clear — these are mostly rare, so it’s not likely you will find them at this stage. If you do, though, the information is extremely valuable. For many of these conditions, you would want specialized help available at birth, which could influence where you deliver. In a few cases, conditions can be treated in the womb.

Ultrasounds at other stages can also be important diagnostic tools, or valuable in other procedures. If you have an amniocentesis, either for chromosomal testing or to check on lung development, using ultrasound guidance during the procedure minimizes the chance of any injury to the fetus.

There are a lot of good reasons to use ultrasounds in pregnancy. This usefulness is sometimes obscured by the fact that, most of the time, there is nothing to detect. When there is, there is huge value.

In terms of risks, the idea that ultrasound might affect development is an old one; I found at least one paper from the 1970s that is already a review article arguing that these concerns are unfounded.

On the particular issue of handedness, there are some mixed results from randomized trials that point to the possibility of a very small increase in left-handedness among boys after use of ultrasound. These effects are very small, statistically weak, and from quite old data. It’s not clear precisely what to make of them, especially given the uncertainty about what the mechanism would be for this relationship.

More concerning, and probably more on your mind: there are many papers, even some published in scientific journals, that speculate on the relationship between ultrasound usage and various disorders (including autism and ADHD). These papers are just that — speculation. People observe an increase in autism over time and they look for causes; they notice ultrasound usage has gone up over time. They speculate on a relationship. Observing two series moving together is not evidence for a causal relationship, though. Many other things have increased over time. This is just not remotely compelling.

Ultrasound is used frequently, for good reason: there is valuable information in it. Like all medical technologies, it should be used as needed. Recreational ultrasounds are not necessary. But the idea that ultrasounds are dangerous is unfounded in the data.

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Is side sleeping important during pregnancy? Comment “Link” for a DM to an article on whether sleep position affects pregnancy outcomes.

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