Are prenatal ultrasound scans really as safe as we think?

First of all, hello and welcome back to my blog! I'm finally back from my summer blogging break and will hopefully be able to keep up with regular updates here. So here is for my back-to-blogging  an article about ultrasounds.

The technology of ultrasound is now very much a part of the modern prenatal follow-up. It allows us to produce an image of the baby inside the womb by using sound waves. It is heplful in detecting malformations, to try to figure out (approximately) the baby's weight and size, to know the baby's sex in advance and to confirm a multiple pregnancy. Today in the western world, this procedure is offered to all pregnant women, at various times during the pregnancy, even if the baby is perfectly healthy. But is it's use (or overuse) really without risks? In which cases does this procedure become a necessary tool, and when would it be better avoided? Reflexion on an intervention that may be taken too lightly...

Ultrasound machines work by sending ultra-sound (high-frequency sound) waves into the womb. They bounce on the foetus as the machine captures the bouncing of the waves, creating an image of the baby and it's organs.

There are good sides to this technology. The image obtained can diagnose or confirm various things in case of doubt, like confirming the pregnancy, diagnosing an ectopic pregnancy or placenta anomalies, to determine if there is more than one baby, to evaluate the amount of amniotic fluid, to see if the baby is developping properly, etc. Knowing these things helps the parents to prepare themselves in consequence, depending on the situation. Knowing when a baby has serious health concerns or life-threatening congenital anomalies can allow the medical team to prepare accordingly at the time of birth. Some parents prefer to know the sex of their baby in advance, and seeing the baby on the screen often helps fathers-to-be to realise that this baby is really there. It makes it more real, more tangible for them.

It is interesting to know that because this technology is relatively new, it is very hard to evaluate the real impact routine ultrasound scans may have on foetuses. These routine scans use frequencies between 3 and 10 megahertz, for up to 60 minutes. At first, we thought that sonic waves had no impact on human cells, but some scientists may now have reasons to question this belief.

These sonic waves can affect living tissue in various ways. First of all, the sonic wave/ray raises the targeted area's temperature by 1˚C, which is generally without risk for an adult. The second reaction causes the gas pockets found in the tissues of mammals to vibrate and cavitate. Many studies have determined that this can be harmful to the tissues concerned. The first study showed that cells produced in laboratories could develop anomalies when exposed to ultrasound waves, and these anomalies could be passed from generation to generation. More studies on mice and rats showed that this technology could be harmful to the nervous system and cause brain developpement issues.  Another study, in 1999 by Brennan and collegues and reported in the New Scientist, found that exposing mice to normal dosages of ultrasound caused a 22% decrease in the cellular division rate, and doubled the ratio of cell destruction in the small intestine. Another study published in the Medical News Today, showed that the prolonged and frequent exposure of pregnant mice to ultrasound caused brain anomalies in the developing mouse foetuses.

So we can ask the following question: even if for an adult the changes could be considered without risk, is it the case for embryos, of weeks old foetuses? What unknown effect could they have on the brain? We still don't know.

Some scientists also question the possible link between the overuse of ultrasound scans aht the ever rising rate of autistic children. It is only a theory for now, no study has proven it yet. Even if we've proven that ultrasound waves caused brain anomalies in mouse foetuses, the scientists involved were unable to determine if it affecter their behavior or not.

Various studies on humans have also showed various possible side-effects of ultrasounds. These include premature ovulation, an increase in premature births and miscarriages, infants with low birth weights, problems with dyslexia and speech and language delay, and more left-handed children. A study from Australia showed that babies who were exposed to more than five ultrasound scans were more likely to develop uterine growth delays. Still, even with these few little studies, we still have no idea of the possible long-term risks of the technolgy.

Even if we have been using ultrasound scans for over twenty years, the results aren't necessarily as precise as we might think. It is possible to get it wrong on many levels, like the gestational age of the baby, and all the weight estimations late in pregnancy have a very large margin of error (sometimes by up to 5lbs). Errors on the sex of the baby, end even on the number of babies are also possible. In some cases, we may decel inexistent malformations, only to discover at birth that the baby is perfectly healthy. In other cases it is possible not to see anything, even if an anomaly is present. A study from 1999 and concerning more than 25 000 women showed that in large hospitals, only 76% of major foetal anomalies were diagnosed. This ratio went down to 36% for small medical centers. Today, the technology has slightly evolved, and the images may be a little clearer, but errors are still very frequent. These mistakes can also be very stressful for some future parents, putting them through test after test, only to discover eventually that everything is in order.

Another interesting study concerned the baby's experience of the ultrasound. It is often observed that the babies undergoing ultrasound scans often move a lot, or even try to ''get away from it''. A study published in the NewScientist examined what kind of experience the baby might have during the ultrasound by placing a small hydrophone in a woman's vagina during the ultrasound. They found that the sound recorded was as loud as a subway train coming into a station when the ultrasound device was pointing at the microphone. Imagine what it does to a foetus's developing ears, only used to muffled sounds and voices and it's mother's heartbeat, to have this incredibly loud sound imposed upon them. No wonder the babies keep trying to get away from it!

Have you ever heard of 3D Ultrasounds? It is an untrasound technique that creates a realistic 3D image of the foetus. To obtain this image, the ultrasound waves have to be imposed on the baby for a very long time in order to gain enough data to create the 3D image, increasing considerably the baby's exposition to the ultrasound waves, and to it's potential risks. There are no medical reasons whatsoever for this procedure. It was only created for the fun to see the baby in 3D before birth. furthermore, 3D and 4D (with sound) ultrasound technicians don't diagnose anything and are not required to report anomalies if they see something that might be wrong on the scan. It is also possible to obtain a little film of the baby moving using this technology.

It is also interesting to mention that the ultrasound technology doesn't only apply to imagery, but other tools used in obstetrics work the same way. They are the doppler and electronic foetal monitor. These two devices are used for the monitoring of the foetal heart. They both use ultrasound, as in the scans, but instead of simple waves, they feature continuous waves, in order to produce an amplified sound of the foetal heart. Even if no image is obtained, it is interesting to know that because of the continuous waves needed to produce sound, one minute of doppler amounts to 35 minutes of regular scan. This is to be taken into account when trying to decide on the way to evaluate a pregnancy early on.  The Doppler is a useful tool in cases where the heart is hard to hear. My suggestion would be to ask the midwife, OB or nurse to try to listen to the heart with a foetoscope first, and to keep the doppler only for if they really can't hear it that way.

In my opinion, when it comes to having a scan or not, the best way to chose would be to weigh the pros and cons in each situation. The final decision rests with the expectant parents on wether they want to take it or not. It is still a relatively new technology allowing us to save lives in some cases, but it may not be necessary to overuse it as we do now. A nice idea would be to try to postpone the scan if it's not an emergency, to as late as possible in the pregnancy. Listen to your intuition. If you are feeling that everything is fine, it probably is the case. If you are having doubts, or are feeling uneasy about something, maybe having a scan done would be a good idea. The thing is to think at what having a scan may bring to you, what information is sought and what it would change before making a choice. If your midwife or doctor wants you to get an ultrasound scan, ask them what they want to know, and you could then decide wether or not to take it.

As for making the pregnancy real, or more tangible for the future father, why not try haptonomy? This alternative method helps the future parents to establish a contact and interact with their unborn child though touch.

Finally, I highly encourage you to explore the following sources listed below. Some are the studies mentionned in my article, other are more articles about ultrasounds.

Have a nice day!

Sources and links:

BRABANT, Isabelle, Une naissance heureuse, Fides, 2013, Montréal, 576 pages.
CYMBALIST, Rivka, The Birth Conspiracy, Curioso BooksCanada, 2011, 280 pages.
FRYE, Anne, Understanding Lab Work in the Childbearing Year, Labrys Press, 1990, 562 pages.
GASKIN, Ina May, Ina May's Guide To Childbirth
, 2012, 496 pages.
GASKIN, Ina May, Birth Matters, Seven Stories, 2011, 250 pages.
LIM, Robin, Eat Pray Doula, Half Angel Press, Bali, 2012, 174 pages ( image) ( image) (image)


  1. 3D Ultrasound
    I wasn't sure if I wanted to do 3D ultrasound pictures or not, because I'm sure most people can agree that the babies kinda look a bit scary in some of them ;) Especially if they are super wiggly. It's hard to get a good focused picture, but it gives you a good look of what they'll look like. It's always crazy seeing baby once they're out compared to a 3D! Anyway, we decided to do it for fun, cuz why not?! I'm so glad we did! It was so cute seeing him move around! I swear I can flip through these pictures all day and not get bored seeing our little boys face :M-F 10am-8pm Saturday and Sunday 10am-4pm.
    3d ultrasound

  2. I like the valuable information you provide in your blog. Radlabs medical diagnostics center will also provides quality and high end Ultrasound scan services in Hyderabad. Thanks for posting useful information.
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  3. The blog was absolutely fantastic! Lot of great information which can be helpful in some or the other way. Keep updating the blog, looking forward for more contents...Great job, keep it up. 3d ultrasound


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