When I was pregnant, I assumed ultrasounds were just harmless sound waves with no effects on the body. I’ve since found out otherwise - there are thermal and mechanical effects. Now in theory this shouldn’t happen at diagnostic levels, but there is a body of studies saying maybe that’s not the case.
There are a lot of animal and cell studies that show harm at low exposure levels. The only large randomised trials (where one group got assigned more scans, one less or none) looking at human effects are pretty old (80s-90s), with mostly observational trials since then (and not many of those either). Some of the old RCTs found increased miscarriage and IUGR in the more scanned group, and a large Swedish study found an increase in left handedness in boys. This was when the machines were much weaker and scans were about 3 mins. Other studies found no effects.
However, in 1992 the max allowed power of the machines was raised 8-fold by the FDA, and there have been very few safety studies at the new much higher intensities. This UK gov white paper is a very thorough review of the literature with conclusions at the end: assets.publishing.service.gov.uk/media/5a7dfba8ed915d74e33ef48e/RCE-14_for_web_with_security.pdf
The summary is on the UK Government page and the wording doesn’t exactly fill me with confidence! www.gov.uk/government/publications/ultrasound-what-it-is-how-it-works-and-the-impact-of-exposure/ultrasound-what-it-is-how-it-works-and-impact-of-exposure#are-there-any-risks-from-ultrasound-scans
Saying there is “very little” information and there could be subtle neurological effects. In total contrast to “perfectly safe” as the NHS told me.
Likewise this statement from an RCOG paper from 2015: “Most epidemiological ultrasound safety studies consider the use of diagnostic ultrasound at around
18 weeks of gestation or later and there are no epidemiological data specifically addressing exposure
of human embryos to diagnostic ultrasound. In addition, most epidemiological evidence derives from
B-mode scanners in commercial use 20–25 years ago, whereas the acoustic outputs from modern devices
have increased 10- to 15-fold over the last decades.35 If there are adverse effects of ultrasound during
pregnancy which are dose- and time-dependent during embryonic or fetal development, then the
available epidemiological data are so limited as to preclude any meaningful conclusions to be drawn.”
www.rcog.org.uk/media/5vvly24v/sip-49.pdf?
There’s been concerning animal studies, like diagnostic ultrasound affecting neuronal migration in mice, and causing mice to be less social and more hyperactive.
pmc.ncbi.nlm.nih.gov/articles/PMC1538990/
https://pubmed.ncbi.nlm.nih.gov/24249575/
I can’t say how well animal studies relate to humans (the first paper theorises this) but neuronal migration disorders in humans manifest in a number of ways, like developmental delay.
There is a plethora of articles summarising the issues, all with references. Here are a couple:
https://sarahbuckley.com/ultrasound-scans-in-pregnancy-your-questions-answered/
https://townsendletter.com/ultrasound-j-west/#fn46
- this journalist actually found and compiled 50 Chinese studies in women who were about to get abortions, where they used advanced techniques to examine the cells after abortion, and found all sorts of cell and tissue damage at just a few minutes of diagnostic ultrasound exposure. There is a book on Amazon though I haven’t read it. This is one study example: pubmed.ncbi.nlm.nih.gov/26782527/
www.fda.gov/radiation-emitting-products/medical-imaging/ultrasound-imaging#benefitsrisks
The FDA, RCOG and UK government basically say “we think it’s safe but we don’t really know, more studies are needed as most of them are old and irrelevant, there might be subtle neurological effects, so don’t go to 4D scan boutiques!” - but 4D scan places are everywhere and allowed to be open? They also say scans should follow the ALARA (as low as reasonably achievable) principle and limit exposure and time to the lowest needed to get clear images, but apparently a lot of techs don’t even know where the indices are on their own machines and just use preset settings, and hover over the face etc to show parents their baby.
I am actually quite shocked by this. Of course there are clear benefits, but I wish I had been told the potential risks and lack of robust modern safety evidence (it would be impossible to do randomised trials now as no-one would agree to 0 scans! It’s routine care) - you can’t really prove a scan did or didn’t cause some issue in your baby. If I’d known I definitely wouldn’t have paid for a reassurance scan and might have declined the 1st trimester dating one as I knew my dates and had done an NIPT blood test for Down’s.