The aim of this study was to investigate sex-related differences in the prenatal development of early oral, lingual, pharyngeal, and laryngeal motor activities. Sonographic images of oral–upper airway regions were observed in 85 healthy fetuses (43 males, 42 females; mean gestational age 24wks 3d [SD 0.69]; range 15–38wks). Biometric data on morphologic development and associated motor patterns were compared across second and third trimesters. Results showed that while males and females demonstrated statistically similar patterns of general physical growth (p>0.05), significant differences in development of specific lingual and pharyngeal structures were present (p<0.05). Significant differences were found for laryngeal and pharyngeal motor activity, and oral–lingual movements (p<0.05). Complex oral–motor and upper airway skills emerged earlier in females, suggesting a sex-specific trajectory of motor development. It was concluded that differential patterns of prenatal motor development may be important in defining sex-specific indices of oral skill maturation.