No statistically significant difference was observed in the number or duration of prenatal ultrasonographic scans across the entire pregnancy of children with later autism spectrum disorder (ASD) compared with controls with non-ASD developmental delay or typical development, according to a study published in JAMA Pediatrics.
However, the researchers did find a significantly greater mean depth of ultrasonographic penetration in the ASD group compared with the developmental delay group in the first trimester and with the typical development group in the first and second trimesters.
N. Paul Rosman, MD, from the Department of Pediatrics at the Boston University School of Medicine, Boston Medical Center, and colleagues conducted a case-control study to quantify prenatal ultrasound exposure by the frequency, timing, duration, and strength of ultrasonographic scans in children with later ASD, developmental delay, and typical development. Participants included 107 patients with ASD, 104 controls with developmental delay, and 209 controls with typical development. Participants were identified from medical records based on prenatal care and delivery at the Boston Medical Center from July 1, 2006, through December 31, 2014, with a gestational age at birth of at least 37 weeks. Data were analyzed from May 1, 2015, through November 30, 2017.
Ultrasonographic exposure was quantified by the number and timing of scans, duration of exposure, mean strength (depth, frame rate, mechanical index, and thermal index), and time of Doppler and 3- and 4-dimensional imaging. Among participants with ASD and controls with developmental delay and typical development, ultrasound exposure was quantified and compared per trimester and for the entire pregnancy, with adjustment for infant sex, gestational age at birth, and maternal age.
A total of 420 participants were included (328 boys [78.1%] and 92 girls [21.9%]; mean age as of January 1, 2016, 6.6 years). The ASD group received a mean of 5.9 scans, which was not significantly different from the 6.1 scans in the developmental delay group or the 6.3 scans in the typical development group. Compared with the typical development group, the ASD group had shorter duration of ultrasound exposure during the first (290.4 seconds vs 406.4 seconds) and second (1687.6 seconds vs 2011.0 seconds) trimesters but no difference in the number of scans.
The ASD group had greater mean depth of ultrasonographic penetration than the developmental delay group in the first trimester (12.5 cm vs 11.6 cm). The ASD group had greater mean depth than the typical development group during the first (12.5 cm vs 11.6 cm) and the second (12.9 cm vs 12.5 cm) trimesters.
“In this detailed study of prenatal use of ultrasonography, we found no significant difference in the number or duration of prenatal ultrasonographic scans across the entire pregnancy in children with later autism compared with controls with non-ASD developmental delay or typical development,” the authors concluded. “Children with ASD had fewer overall ultrasonographic examinations during the first trimester, the period during which we hypothesized that risk would be greatest.”
In a related editorial, Sara Jane Webb, PhD and Pierre D. Mourad, PhD, from the Seattle Children’s Research Institute in Washington, stated, “The findings are overall consistent with reports that suggest prenatal ultrasonography is not a sufficient single causal factor in ASD. However, the potential for ultrasonography to act as an environmental stressor in a genetically vulnerable system remains. The goal of seeking mechanistically valid environmental modifiers of child outcomes remains an important one, particularly if the environmental insult can be limited, modified, or regulated.”
- Rosman NP, Vassar R, Doros G, et al. Association of Prenatal Ultrasonography and Autism Spectrum Disorder. JAMA Pediatr. 2018 Apr 1;172(4):336-344. doi: 10.1001/jamapediatrics.2017.5634
- Webb SJ, Mourad PD. Prenatal Ultrasonography and the Incidence of Autism Spectrum Disorder. JAMA Pediatr. 2018;172(4):319-320. doi:10.1001/jamapediatrics.2017.5685