As most readers of this blog know I have been a longstanding proponent of the need for additional safety studies on the use of prenatal ultrasound. It is easy to see why a book entitled “Ultrasound and Autism” would pique my interest. The book is authored by Jack Rabin and I bought it from Amazon for $15.95. I thought it was a little bit overpriced considering it was paperbound and only 85 pages long. The book itself is an easy read that would take less than one hour to go from cover to cover. The author is a retired general physician who emphasized neurology in his long-standing practice at Long Beach, California.
The book is detailed and reflects the amount of care the author placed in reviewing the literature. In the end the main intent of establishing a correlation between autism and prenatal ultrasound based on prevalence rates is only suggested and never proven. As an example, in this country from the year 2000 until 2009 there was a direct correlation between per capita consumption of mozzarella cheese (in pounds) and the total number of degrees awarded in civil engineering doctorates. A correlation between 2 variables does not necessarily imply that one causes the other. In this regard, the author’s insistence of a correlation between the steep rise in prevalence rates for autism and the use of prenatal ultrasound is thus a logic fallacy. Furthermore, many of the salient population studies that could have been used to support his claims are never discussed. A controversial example linking ultrasound and autism pertains to the Amish population within the US who almost never use ultrasounds during their prenatal care and seemingly have a lower prevalence of autism. Similarly striking, autism may be unheard of in third world countries like Somalia, but once these indigenous people emigrate to industrialized nations, the rates of autism soar.
The author does make a good point that more safety studies on prenatal ultrasound should be performed. The human literature indicates the presence of subtle neurological maldevelopment defects attributed to ultrasound or Doppler use, including: dyslexia, left-handedness, delayed speech development, and low birth weight. At present different safety boards have stated their opinion that prenatal ultrasound offers no benefits for low risk pregnancies. According to a study known as the Routine Antenatal Diagnostic Imaging with Ultrasound (RADIUS) trial which examined 37,505 women, “Routine scans do not seem to be associated with reductions in adverse outcomes for babies or in health services use by mothers and babies.” Still the number of such tests has increased over the years and low risk pregnancies may end up receiving 4 to 5 of these exams.
Unfortunately epidemiological studies in humans are plagued by uncontrolled variables. In the case of a pregnant patient multiple examinations may be performed with different types of equipment and the amount of energy that a patient receives varies from examiner to examiner. In this regard investigators have focused their attention on animal studies for which several groups have shown learning problems, task performance differences, and even neuropathological brain abnormalities including deficits of brain migration to the cerebral cortex. Although these deficits are usually ascribed to thermal and mechanical effects caused by the sound waves there are other recently uncovered mechanisms that may be playing a role. In effect, although not cited in Dr. Rabin’s book, the recent literature indicates that ultrasound may cause pores in cell membranes leading to the possible formation of gap junctions between them.