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Is There Scientific Evidence Suggesting Risks Associated With Prenatal Ultrasounds?

Several questionable sources are spreading alarms about the possible dangers of prenatal ultrasound exams (sonograms). An example is Christine Anderson’s article on the ExpertClick website. In the heading, it says she “Never Liked Ultrasound Technology.”

[She] has never been sold on the safety using Ultrasounds for checking on the fetuses of pregnant women, and for the last decade her fears have been confirmed with a series of studies pointing to possible brain damage to the babies from this technology.

Should We Believe Her?

Should we avoid ultrasounds because Anderson never liked them? Should we trust her judgment that her fears have been confirmed by studies? Who is she?

“Dr.” Christine Anderson is a pediatric chiropractor in Hollywood who believes a lot of things that are not supported by science or reason. Her website mission statement includes

We acknowledge the devastating effects of the vertebral subluxation on human health and therefore recognize that the spines of all children need to be checked soon after birth, so they may grow up healthy.

It also states that “drugs interfere… and weaken the mind, body, and spirit.” Anderson is a homeopath, a craniosacral practitioner, a vegan, and a yoga teacher. She advises her pregnant patients to avoid toxins by only drinking filtered water and only eating organic foods. She sells her own yoga DVD.

In her own pregnancies she refused ultrasound and other prenatal screening tests. This was her idiotic reasoning:

I trusted in my body’s innate wisdom that if the pregnancy was moving forward, then everything was going OK in my baby’s development.

Apparently on her planet if a pregnancy has not spontaneously aborted that means the baby is developing normally, and no abnormal child is ever born. And perhaps all the children are above average?

She believes in many alleged benefits of chiropractic that are not substantiated by any evidence. She says that our emotions create chemical changes in our bodies that can affect our developing babies; and that chiropractic helps to keep those feel good chemicals flowing freely. She believes that chiropractic frees up any interference to the nervous system and since the nervous system controls all the functions in the body, chiropractic manipulations allow the organs to optimally process any toxins they encounter. She believes getting regular chiropractic care reduces labor times.

Based on this, I am not impressed by her medical judgment or her understanding of biology or science, but that doesn’t necessarily mean she is wrong about ultrasound. What does she say?

Alleged Risks of Ultrasound According to Anderson

  • Ultrasound heats the tissue and researchers suspect that the waves cause small local gas pockets which vibrate and collapse called cavitation. The gas can reach up to temperatures of thousands of degrees (Celsium) [sic] leading to production of potentially toxic chemical reactions.
  • Studies done on mice have shown intestinal bleeding caused by changes in the cells. Scientists conclude that there would be similar effects in humans.
  • Ultrasound has been linked to the following abnormalities:
    • Left handedness in children who are supposed to be right-handed. Although there is nothing inherently wrong with being left handed, the change is attributed to a subtle damage to the brain. Males are more affected than female fetuses, probably because the male brain develops later.
    • Early labor, premature birth, miscarriage, low birth weight, poorer health at birth, and perinatal death.
    • Increased learning disabilities, epilepsy, delayed speech development, dyslexia

She also alleges that no studies have been done to prove the safety of these devices. This is demonstrably false.

Elsewhere, prenatal ultrasound exposure has even been accused of causing autism although a study found no association.

Risks According to Scientists

Obstetricians and radiologists who have evaluated the peer-reviewed literature have found no evidence of harm except for an apparent correlation between ultrasound exposure and left-handedness (in males only!).  Such odd-sounding correlations are usually not significant, and are mostly good for a chuckle.

Experts place little reliance on the mouse studies, since the dosages tested were higher than what humans are exposed to and since no corresponding clinical consequences have been detected in humans. Nevertheless, they acknowledge theoretical reasons for concern, and they recommend that medically unnecessary ultrasounds be avoided under the precautionary principle.

Does Routine Ultrasound Affect Outcomes?

A large study (15,530 women) published in The New England Journal of Medicine found that routine screening did not reduce perinatal morbidity and mortality.  There were no significant differences in the rate of preterm delivery, distribution of birth weight, or outcomes within the subgroups of women with multiple gestations, small-for-gestational-age infants, and post-date pregnancies. Finally, the detection of major anomalies by ultrasound examination did not alter outcomes. The authors pointed out that routinely screening more than 4 million pregnant women annually in the United States at $200 per scan would increase costs by more than $1 billion.

A Finnish study found that perinatal mortality was significantly lower in the screened than in the control group (4.6/1000 vs 9.0/1000); but this was attributed to improved early detection of major malformations which led to induced abortion. All twin pregnancies were detected before the 21st gestational week in the screening group compared with 76.3% in the control group; perinatal mortality in the small series of twins was 27.8/1000 vs 65.8/1000, respectively.

Caveats: These studies did not look for long-term consequences like learning disabilities. And there are other considerations besides morbidity and mortality. Ultrasound can reassure patients or allow them to plan ahead for multiple births or abnormal infants, and it can guide obstetric management.

Reasons for Doing Ultrasounds

Ultrasounds can detect fetal abnormalities and can help guide obstetric care by detecting problems like multiple fetuses and placenta previa. There are many legitimate reasons for doing them, especially in high-risk pregnancies or when a specific problem is suspected.

Reasons for Not Doing Routine Ultrasounds

False alarms can be raised. Apparent abnormalities may cause worry but turn out not to be significant. Placenta previa detected early in pregnancy frequently resolves before delivery.

There is no way to completely rule out the possibility of a low risk of long-term consequences. Trying to identify such consequences by even the most careful epidemiologic studies is fraught with pitfalls, since if you look for every possibility you will inevitably find a few spurious correlations. Experts agree that routine ultrasound screening is not necessary in low-risk pregnancies and that ultrasounds for nonmedical reasons should be discouraged.

Some nonmedical uses are particularly objectionable. Ultrasounds are being used in India and elsewhere to determine sex for the purpose of aborting undesired female fetuses.  Ultrasound is being commercially promoted for “keepsake” pictures and movies like this 5 minute video. Tom Cruise was roundly criticized by doctors for buying his own ultrasound machine for home use.


There is no reason to fear prenatal ultrasounds that are ordered by science-based medical professionals and performed by qualified technicians, but it seems prudent to exercise caution and not do them for frivolous reasons.

Considering that Anderson practices homeopathy, subluxation-based chiropractic, and craniosacral therapy, disparages drugs, and manipulates the spines of newborn infants, I think her own practices are far more worrisome than the ultrasounds she fears.

*This blog post was originally published at Science-Based Medicine*

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