Objectives: To investigate the best time of examination and section chosen of routine prenatal ultrasound screening for external ear abnormalities and evaluate the feasibility of examining the fetal external ear with ultrasonography.
Methods: From July 2010 until August 2011, 42118 pregnant women with single fetus during 16-40 weeks of pregnancy were enrolled in the study. Fetal auricles and external auditory canal in the second trimester of pregnancy were evaluated by routine color Doppler ultrasound screening and systematic screening. Ultrasound images of fetal external ears were obtained on transverse-incline view at cervical vertebra level and mandible level and on parasagittal view and coronal view at external ear level.
Results: Five fetuses had anomalous ears including bilateral malformed auricles with malformed external auditory canal, unilateral deformed external ear, and unilateral microtia. The detection rate of both auricles was negatively correlated with gestational age. Of the 5843 fetuses undergoing a routine ultrasound screening, 5797 (99.21%) had bilateral auricles. Of the 4955 fetuses following systematic screening, all fetuses (100%) had bilateral auricles. The best time for fetal auricles observation with ultrasonography is 20-24 weeks of pregnancy.
Conclusions: Detection of external ear abnormalities may assist in the diagnosis of chromosomal abnormalities.