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Sinistrality-a side-effect of prenatal sonography: A comparative study of young men - paper from 2001

Although ultrasound during pregnancy is used extensively, there is little published on adverse fetal effects. We undertook a cohort study including men born in Sweden from 1973 to 1978 who enrolled for military service. We estimated relative risks for being born left-handed according to ultrasound exposure in fetal life using logistic regression analysis. Eligible for the study were 6,858 men born at a hospital that included ultrasound scanning in standard antenatal care (exposed) and 172,537 men born in hospitals without ultrasound scanning programs (unexposed). During the introduction phase (1973 to 1975) there was no difference in left-handedness between ultrasound exposed and unexposed (odds ratio = 1.03, 95% confidence interval (CI) = 0.91 to 1.17). When ultrasonography was offered more widely (1976 to 1978), the risk of left-handedness was higher among those exposed to ultrasound compared with those unexposed (odds ratio = 1.32, 95% CI = 1.16 to 1.51). We conclude that ultrasound exposure in fetal life increases the risk of left-handedness in men, suggesting that prenatal ultrasound affects the fetal brain.1

While this article may have proven that left handedness may be affected by prenatal ultrasound screening, is there any evidence suggesting that prenatal ultrasound screening may negatively impact the fetus?

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    Why is left-handedness negative or risky? Also, your quoted text mentions no effect from 1973 to 1975, and it would be interesting to see if there was an increased left-handedness birth rate that somehow correlates with the [assumed] increase in ultrasounds being performed on pregnant women. – Randolf Richardson Dec 12 '11 at 3:59
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    The quote you give is simply reporting an effect, not a pronouncement on harm. The last sentence of the paper suggests that the change in handedness could be a side effect of some brain injury due to the ultrasound, which is hypothesis of the mechanism and not a judgement of harm either. – Joel Rein Dec 12 '11 at 4:08
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    I would also wonder about the strength of the ultrasound technique used in the 70s as compared to now, as well as controlling for the handedness of the parents. While it can be tricky to determine if the trait is heritable (en.wikipedia.org/wiki/Handedness#Is_left-handedness_genetic.3F), that a child born to two lefties has a 26% chance of lefthandedness could skew their results. As for technique strength, the ultrasound units of that day may have been putting out far more energy than a more efficient, modern unit, so these findings may no longer be relevant anyway. – mmr Dec 12 '11 at 5:15
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    @Randolf Richardson: you are over-reading the quote. Risk is used in its statistical sense here, they are not saying left-handedness is risky or negative, they are just using it as an (incredibly rough) measure of brain wiring. What they are stating is that if ultrasounds can affect handiness, they are affecting brain wiring. Obviously there are many confounding factors in this, although I would doubt that over the corse of 5 years the trend in control of handedness by the parents had changed so much. – nico Dec 12 '11 at 8:11
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    So there is this one and only study which has been done 40 years ago, and found some weak correlation. Doesn't sound like much of a proof. Especially given that usage of USG has risen to almost 100% in developed countries, however left-handness levels remain pretty much the same. – vartec Dec 12 '11 at 10:51
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Per John P Newnham et.al. in 2004, the results of a randomized controlled trial investigating possible effects of multiple prenatal ultrasound scans on growth and development in childhood showed that "there were no significant differences indicating deleterious effects of multiple ultrasound studies at any age as measured by standard tests of childhood speech, language, behaviour, and neurological development.

Interpretation: Exposure to multiple prenatal ultrasound examinations from 18 weeks’ gestation onwards might be associated with a small effect on fetal growth but is followed in childhood by growth and measures of developmental outcome similar to those in children who had received a single prenatal scan. In view of the widespread and liberal use of this technology we are responsible for ensuring the safety of its use.

These results also provide reassurance that multiple prenatal ultrasound scans are not followed by smaller body size in infancy or childhood. Per FDA, ultrasound scans should be done only when there is a medical need, based on a prescription, and performed by appropriately-trained operators. Ultrasound waves can heat the tissues slightly and in some cases, it can also produce small pockets of gas in body fluids or tissues (cavitation). The long-term consequences of these effects are still unknown. Combining ultrasound and MRI is essential for the prenatal diagnosis of teratomas and neuroepithelial tumors and determining their prognosis.

The overall absence of any deleterious effects of prenatal scans on childhood development is consistent with results from two other studies mentioned below.

  1. Per Salvesen KA et.al. in 1993, children who were routinely exposed to ultrasonography in utero showed no statistically significant differences in growth during childhood compared to control children.

No significant differences between ultrasound-screened children, and their controls, were found in mean body weight, or height, at birth and at all the subsequent visits to the health centers. However, the repeated-measures analysis of variance in the subsample indicated that growth from birth to 7 years of age differed significantly (p = 0.02) between screened and control children of mothers who reported smoking at the first antenatal visit.

  1. Per Sturla H. Eik-Nes et.al. in 1999, "epidemiological evidence does not indicate any association between diagnostic ultrasound exposure during pregnancy and reduced birthweight, childhood malignancies or neurological maldevelopment."

The present paper summarizes some of the epidemiological studies of in utero ultrasound exposure and subsequent childhood development. Emphasis is placed on birthweight, childhood malignancies and neurological development. A meta-analysis, including neurological outcomes such as handedness, speech development, motor development, hearing and vision, is presented.

Please note that this answer does not constitute medical advice. It is only meant to summarize published research related to the topic and limited to the cited sources. Consult your physician about what these results may mean for your health.

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