Lack of mandibular movement manifested by absent fetal swallowing: a possible factor in the pathogenesis of micrognathia.

This study was performed to assess the association of lack of mandibular movement as manifested by absent fetal swallowing and micrognathia in a nonrestrictive intrauterine environment. Over a 5-year period, 14 fetuses with sonographic findings of polyhydramnios (amniotic fluid index [AFI] more than 20 cm), absent mandibular movement, and a nonvisualized fetal stomach, all consistent with absent fetal swallowing, were followed. A group of 14 fetuses, each with polyhydramnios (AFI more than 20 cm), yet with sonographic detection of fetal swallowing, served as controls. All gravidas in both groups were normoglycemic throughout gestation. Subsequent mandibular development was assessed at delivery or autopsy. Analysis of the data revealed that in the study group, 12 of these infants were liveborn, and two were stillborn. Eleven of the liveborn infants had an early neonatal death. All 14 infants of the study group demonstrated micrognathia. None of the control infants (all of whom survived) had micrognathia. In conclusion, this study supports the concept that normal mandibular growth may depend on the presence of mandibular movement during intrauterine development.