Abstract： Objective: To explore the diagnosis value of fetal external ears by using ultrasound. Methods: Of 400 fetuses, each 100 cases were selected randomly during gestational 11～14 weeks, 16～20 weeks, 24～28 weeks and 32～36 weeks. Bilateral external ears were observed by using the multi-views and multi-angles of prenatal ultrasonography. To summarize the display rate, the best time and scan sections of ultrasound. Results: The fetal external ear was negatively correlated with gestational age(r=-0.994, P=0.006). With the increasing of gestational age, external ear acquisition rate was showed a downward trend. During gestational 11～14 weeks, it was showed the highest rate, and up to 100%, and the its lowest age was during gestational 32～36 weeks. The mastoid section coronal scan and foramen magnum coronal scan were the best sections during gestational 11～14 weeks of gestation. The left or right temporal parasagittal plane was the best sections to observe the morphology of fetal external ears. The mastoid section coronal scan, foramen magnum coronal scan and left or right temporal parasagittal plane was negatively correlated with gestational age, regression equation: Y=242.239-5.674X(r=0.938, P=0.018); Y=242.092-5.547X(r=0.944, P=0.016); Y=194.375-1.392X(r=0.605, P=0.021). According to the number of morphology the fetal external ear, gestational 16～20 weeks and gestational 24～28 weeks was the best period. Gestational 11～14 weeks display difference. Comparison of the total acquisition rate of fetal ear morphology in different gestational weeks, χ2=24.00, P=0.293. Conclusion: In different gestational weeks, the display rate of the fetal external ear is different, gestational 11～14 weeks is the highest in the display rate of the external ear.
