Let鈥檚 be honest鈥攑regnancy is basically a nine-month exercise in overthinking. Is that sushi safe? Should I be sleeping on my left side? And what, exactly, is in prenatal vitamins anyway? Somewhere on that ever-expanding list sits the ultrasound: a routine, widely used tool that some corners of the internet have started side-eyeing with suspicion.
In this article, we鈥檙e turning down the noise and turning up the facts. We鈥檒l break down why ultrasounds are used, what science says about their safety, and why your best source of information still isn鈥檛 your friend鈥檚 cousin鈥檚 doula鈥檚 wellness blog.
Why Ultrasounds Are a Pregnancy Staple
Ultrasounds are more than just your baby鈥檚 first photo op (although, let鈥檚 admit it鈥攖hat blurry little blob is adorable). These scans give healthcare providers vital info, including:
- Estimating your due date based on fetal measurements.
- Checking for ectopic pregnancies, where the embryo implants outside the uterus.
- Monitoring fetal heart rate, growth, and movement.
- Spotting placenta previa, where the placenta covers the cervix (not ideal for delivery).
- Determining the baby鈥檚 sex, if you want to know鈥攁nd if the baby feels like cooperating.
In short, ultrasounds aren鈥檛 just routine鈥攖hey鈥檙e revelatory.
But... Is It Safe?
Here鈥檚 where things get noisy. The internet is buzzing with fears about 鈥渦ltrasound heating,鈥� especially around Doppler ultrasound, which uses continuous sound waves to measure blood flow.
Yes, it鈥檚 true that ultrasound waves can be absorbed by tissue and converted into heat鈥攁nd Doppler ultrasound, which is used to assess blood flow, is particularly noteworthy here. Unlike routine B-mode scans that use short, pulsed sound waves, Doppler uses continuous or high repetition rate signals, delivering more energy to a single spot. This makes it more likely to generate heat, especially later in pregnancy when fetal bone tissue鈥攚hich is excellent at absorbing sound energy鈥攃an transfer that heat to nearby brain tissue. pointed out that up to 75% of this heating can happen within the first 30 seconds of exposure near bone, and that the fetal skull鈥檚 development increases sensitivity to this effect. However, it鈥檚 important to note that all of the studies discussed in that paper were conducted on animal models, including sheep, guinea pig fetuses, and neonatal pigs鈥攏ot humans. Moreover, these findings came from controlled experimental conditions using exposure times and intensities much longer and higher than what is used in standard obstetric practice. Nevertheless, given the findings of this review, and others, Doppler ultrasound is scrutinized more closely for potential thermal effects than standard imaging.
The World Federation for Ultrasound in Medicine and Biology (WFUMB) , stating that:
鈥淏iologically significant temperature increases have been measured, at or near bone/soft tissue interfaces, during exposure to conditions similar to those used in Doppler diagnostic equipment. The effects of elevated temperatures may be minimised by keeping the time for which the beam passes through any one point in tissue as short as possible.鈥�
In clinical practice, this is exactly what trained sonographers and physicians do鈥攖hey move the probe, limit exposure time, and use the lowest settings necessary to get the needed information. As long as Doppler techniques are used judiciously and briefly, the actual risk remains theoretical, not proven.
Then Why the Fuss?
Since 1992, the maximum intensity for diagnostic ultrasound in the U.S. has quietly increased over sevenfold, from 94 to 720 mW/cm虏. What we 丑补惫别苍鈥檛 seen since? Large-scale, population-based studies evaluating whether these higher levels pose new risks. So, the concern isn鈥檛 totally unfounded鈥攊t鈥檚 just not backed by any evidence of harm so far.
Medical societies know this. That鈥檚 why regulatory agencies require real-time output display standards鈥攖hink of them as ultrasound 鈥渟peedometers鈥濃�攕o clinicians can stay within safe operating zones.
TL;DR: Ultrasounds Are (Still) Safe鈥擶hen Used Wisely
Despite higher machine outputs today, expert bodies consistently affirm that the benefits of diagnostic ultrasound outweigh the theoretical risks when performed by trained professionals. That means if you鈥檙e pregnant and wondering whether to get that scan, your best bet is simple:
Ask your doctor鈥攏ot your favourite wellness influencer or your friend鈥檚 naturopath who thinks kale juice is a cure-all.
Sophie Tseng Pellar recently graduated from 每日探花 with a Bachelor of Science (BSc) degree in the physiology program. She will be continuing her graduate studies in the surgical and interventional sciences program at 每日探花. Her research interests include exercise physiology, biomechanics and sports nutrition.
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