The development of anticipation in the fetus: a longitudinal account of human fetal mouth movements in reaction to and anticipation of touch.

Research suggests that fetuses open or close their mouth in relation to directed movements but it is unclear whether mouth opening anticipates the touch or is a reaction to touch, as there has been no analysis so far of (1) the facial area of touch and (2) the sequential ordering of touch and mouth movements. If there is prenatal development of the anticipation of touch we would expect the frequency of fetal mouth opening immediately preceding the arriving hand at the mouth area to increase with fetal age. Fifteen healthy fetuses, eight girls and seven boys, underwent four additional 4-D scans at 24, 28, 32, and 36 weeks gestation. Changes in the frequency of touch for different facial regions indicated a significant decline in touch of the upper and side parts of the face and a significant increase in touching lower and perioral regions of the face with increasing gestational age. Results supporting the hypothesis showed a significant increase in the proportion of anticipatory mouth movements before touch increasing by around 8% with each week of gestational age. Additionally there was a decrease in the proportion of reactive mouth movements decreasing by around 3% for each week of gestational age.