Fetal behavioral responses to the touch of the mother's abdomen: A Frame-by-frame analysis

- Fetuses, particular in the 3rd trimester, selectively respond to external tactile stimulation.
- Fetal maturation affects the emergence of their differential responsivity.
- Fetuses in the 3rd trimester start showing a differential response to tactile stimulation of the abdomen by the mother compared to no stimulation while there is no such differential responsivity in fetuses in the 2nd trimester.

The aim of the present study was to examine whether fetuses respond to the touching of the mother's abdomen, and if they do, whether they differentiate based on familiarity and the source of the touch, utilizing 3D real-time (4D) sonography.Behavioral responses of 28 fetuses (20th to 33rd week of gestation; N = 15 in the 2nd and N = 13 in the 3rd trimester) were frame-by-frame coded using a coding system comprising 20 codes and were analyzed in four conditions, during the touch of the (1) mother, (2) the father, (3) the stranger and in a (4) no-touch, control condition.Fetuses showed differential responses to the touch, in particular in the duration of their reaching out to touch the uterus wall in the four conditions, and self-touch, dependent on the gestational age of the fetus. Fetuses in the 3rd trimester touched the uterus wall significantly longer than fetuses in the 2nd trimester did, when the mother touched compared to the control condition. At the same time, fetuses in the 3rd trimester also touched themselves less during the mother's touch, compared when the stranger touched and also compared to the control condition.This differential response of the older fetuses might be due to the maturation of the central nervous system, and may indicate the emergence of a proprioceptive self-awareness by the 3rd trimester.