Pain is a disruptive event if suffered in the neonatal period, as infants’ pain threshold is lower than that of adults; this is why a minor procedure performed on newborns does not provoke minor pain. Luo et al report that “the pain threshold of newborns is 30%-50% lower than that of adults, and the pain tolerance is lower than that of children of other ages, making the pain perception more intense, lasting and profound for neonates.” [More]
How about for prenatals?