Average daily speech exposure for fetuses

The quality and quantity of speech and language exposure during early childhood is believed to be predictive of language ability during later childhood development. However, the human auditory nervous system comes “online” in utero, at least as early as 23 weeks’ gestation. It has been demonstrated that intrauterine fetal experience with extrauterine sounds during this last trimester of gestation is sufficient to impact auditory brain development and neural responses to speech. Whether fetal exposure to speech affects later childhood language development remains an open and difficult question. To begin to address this question, we collected and analyzed fetal auditory exposure data for sounds generated in the extrauterine environment using small audio recorders worn by pregnant women during the third trimester of pregnancy. Averaged across 2200 h of audio data, daily speech exposure for individual fetus subjects ranged from 2.8 to 5 h, suggesting some newborns may begin extrauterine life with less than 60% of the speech and language exposure of their peers. Whether this variability is associated with variability in subsequent development remains to be seen.