Fetal mouth movements during behavioural states 1F and 2F

The aim of this study was to investigate the characteristics of mouth movements during behavioural states 1F (quiet sleep) and 2F (active sleep) in the near term human fetus. Thirty-six women participated. Fetal heart rate and fetal movements were recorded for 2 hours continuously. Videotapes with enclosed periods 1F and 2F were replayed to record fetal mouth movements in detail. During 1F, regular mouthing movements dominated (present in 74%), while jaw opening, yawn and grimace were only observed in 5 to 16% of the recordings. Tongue protrusion was not observed in 1F. In all 2F periods jaw opening was present (100%), while tongue protrusion, yawn and grimace were also frequently observed. Regular mouthing was observed in 2F in only two fetuses. For regular mouthing and sucking, onset-to-onset intervals of clusters, cluster duration, and number and frequency of movements within clusters were calculated. In all aspects the differences between these two types of movement were statistically significant. Within the clusters of regular mouthing a decline in the mouthing frequency was found. The data on fetal regular mouthing correspond with observations in the neonate.