Prenatal Ultrasound-Safe, So Far

The prenatal ultrasound examination is an example of a medical test widely accepted before it was proven safe for the developing embryo or fetus. Ultrasound imaging has been standard prenatal care for 30 years. Acknowledging that the evidence supporting its acceptance is “far from comprehensive,” Australian researchers set out to fill some major information gaps. Their results, published recently in the British journal The Lancet (12/4/04), were reassuring.

John P. Newnham , MD, and colleagues at the University of Western Australia specifically wanted to know whether there were any adverse effects on the growth and development of the fetus. The Australian researchers had already conducted a clinical trial that found multiple ultrasound examinations produced an “unexplained and significant increase in the proportion of growth-restricted newborns.” Now the researchers wanted to know what happens to these babies as they grow up. Assessments were done on children whose mothers had participated in five studies of ultrasound imaging. The children were tested nearly every year between the ages of one and eight. The mothers had been randomly assigned to receive either a single ultrasound or two ultrasounds plus another test called umbilical artery Doppler flow velocity waveform.

At one year of age and thereafter, the size of the children was similar whether their mothers had received just the one ultrasound or multiple testing. There were no differences between the two groups in terms of speech, language, behavior, and neurological development. “Our studies have provided strong reassurance that the intensity of ultrasound used in traditional imaging studies appears to be safe,” wrote Dr. Newnham in an e-mail. He stressed that he is referring to the ultrasound intensity used between 1989 and 1992 when the five studies were conducted. “But newer machines have higher outputs and continuing research is required,” he cautioned. “The greatest danger to a pregnant woman and her unborn child is an unskilled operator who may make an incorrect diagnosis, not the machine itself. That is why our two countries [ Australia and the U.S. ] have worked so hard to have high standards and credentialing of sonographers.”