A Scoping Review of Excessive Prenatal Ultrasonography as a Potential Risk Factor for Autism

Abstract

For the past several decades, abdominal/pelvic prenatal ultrasonography (P-USG) has been the most significant technology used in obstetrics. There has been a tremendous increase in use throughout the world and there have been many improvements in the technology used. However, there are aspects of the technology such as frequency, exposure time, thermal and cavitation exposure indices, and increased acoustic output of the ultrasonic waves that possibly could be harmful to the embryo/fetus. In particular, prolonged exposure may increase susceptibility to Autism Spectrum Disorder (ASD). Along with the increasing use of P-USG, there has been a similar increase in the incidence of ASD. The diagnosis of ASD has been found to be more common in geographic areas with a more affluent ethnicity, high socioeconomic status, and high parental education. These are also areas where prenatal ultrasonography is readily available and affordable. Given that there are biophysical risks from P-USG, especially in non-medical settings, P-USG may emerge as a possible risk factor for ASD. The past history of radiography provides a historical perspective: the predominant past opinion years ago was that exposure to X-rays during pregnancy caused no significant risk to a fetus. However, the association between X-ray exposure and childhood leukemia was only established 40 years after X-ray use began. This review focuses on the literature which supports the generation of the hypothesis that excessive P-USG usage may be a factor in the etiology of ASD.