Rosman NP, et al. - Experts aspired to quantify prenatal ultrasound exposure by the frequency, timing, duration, and strength of ultrasonographic scans in children with later autism spectrum disorder (ASD), developmental delay, and typical development. In the ASD group, a significantly greater mean depth of ultrasonographic penetration was noted compared with the developmental delay group in the first trimester and compared with the typical development group in the first and second trimesters.