[Odontogenesis in the human fetus: an echographic study].

During real-time ultrasound observation of swallowing movements in the human fetus, changes in the echostructure of the jaws were detected. Dense linear echoes (2-6 mm) arose symmetrically in the superior and inferior jaws from the median to the distal level with increasing gestational age. Their localisation and onset suggested they might represent tooth germs. The comparison between radiography after birth and pre- and postnatal echography confirmed that these particular echoes were indeed calcified tooth germs. The implications of this observation will be discussed in terms of fetal growth maturation and gestational age.