Fig 1.
A schematic representation of the timeline of fetal visual and auditory perception.
In utero, acoustic stimulation is available, while only luminosity is available to the visual system. At birth, although the physical barrier of the abdomen is no longer in place, the acuity of the fetal visual system is very poor. At several months post-partum, visual acuity has improved but remains poorer than that of adults until approximately 6 months. Meanwhile, the auditory system, despite having relatively elevated thresholds compared to adults, especially in higher frequencies, is nevertheless responsive to a broad range of frequencies (see text for details) from approximately 24 gestational weeks onward.
Fig 2.
Schematic illustration of sensory input to the fetus.
The diagram highlights the relative penetrance of vibrotactile and acoustic stimuli, which can be transmitted directly as pressure waves, compared to light, whose photons are absorbed by the abdomen, reflected, and scattered, preventing the transmission of images. All icons are original works or reused under a CC-BY4.0 license. “Vibrotactile stimuli” icon obtained from https://icon-icons.com/icon/touching-ngers/64385; “heartbeat” icon by M2n obtained from https://thenounproject.com/icon/heartbeat-5770628/.