Ultrasonographic ear length measurement in normal second- and third-trimester fetuses

Objective: We sought to develop a nomogram for fetal ear length measurements from a large population of healthy second- and third-trimester fetuses and to investigate the correlation of fetal ear length with other standard fetal biometry measurements, as follows: biparietal diameter, head circumference, abdominal circumference, femur length, and humerus length. Study Design: Ear length measurement was obtained prospectively in 4240 singleton fetuses between 15 and 40 weeks’ gestational age. Either complete data for normal karyotype on amniocentesis or normal infant examination at birth or both were available in 2583 cases. These constituted the final study population. Results: A nomogram was developed by linearly regressing ear length on gestational age (Ear length [in millimeters] = 1.076 × Gestational age [in weeks] – 7.308). There was a high correlation between ear length and gestational age (r = 0.96; P = .0001). Conclusion: The results of this study provide normative data on growth of fetal ear length from 15 to 40 weeks’ gestation. Good correlation was also observed between ear length and other fetal biometric measurements (biparietal diameter, head circumference, abdominal circumference, femur length, and humerus length). (Am J Obstet Gynecol 2000;183:230-4.)