Morphogenesis of the secondary palate in normal and hydrocortisone-treated hamsters.

Fetal palate morphogenesis was studied in normal and hydrocortisone-treated hamsters. Formation of the normal palate was completed between day 12:00 and 13:00 of gestation, and during this period 8 distinct developmental stages were recognized. Following hydrocortisone administration the early stages, during which vertical-to-horizontal shelf reorientation occurs, appeared to be unaffected, but subsequent fusion between opposing shelves was inhibited. Both chronological age and fetal weight provided reliable criteria for stages of normal palatal development. Following hydrocortisone administration, however, fetal weight was a poorer indicator of stage of palate organogenesis than chronological age.