Fetal ear length measurement: a useful predictor of aneuploidy?

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Abstract
To determine the usefulness of short ear length (EL) measurement in the prenatal detection of fetuses with chromosomal abnormalities. Fetal EL measurements, routine biometry and complete anatomic survey for fetal abnormalities were prospectively performed by antenatal sonography. One thousand eight hundred and forty-eight patients with singleton pregnancies undergoing genetic amniocentesis in the second or third trimester. Complete data for EL, biometry and anatomic survey for major structural abnormalities and minor sonographic markers of chromosomal abnormality were available in 1311 fetuses. Of these, 48 (3.7%) had an abnormal karyotype and 1263 (96.3%) had a normal karyotype. Using an EL measurement of ≤10th percentile for corresponding gestational age in normal fetuses as abnormal cut-off values, detection rates for chromosomal abnormalities by short EL were determined. Among the 48 abnormal karyotypes, 34 were considered significant, and 11 of these 34 (32.4%) fetuses had short EL. In 14 cases, the karyotypic abnormality was considered non-significant and fetal EL was normal in all cases. Of the 34 fetuses with significant chromosomal abnormalities, six (17.6%) on antenatal sonography had no detectable abnormal findings, other than short EL. An increased biparietal diameter (BPD)/EL ratio of ≥4.0 was also noted in fetuses with an abnormal karyotype, but the sensitivity and predictive value of increased BPD/EL ratio alone or increased BPD/EL ratio in combination with short EL was no better than the sensitivity and predictive value of short EL alone. A combination of short EL and abnormal ultrasound, however, gave a much higher positive predictive value (46%) for significant chromosomal abnormalities. Our findings suggest that in women at high risk for fetal chromosomal abnormality, a short fetal EL measurement on prenatal ultrasound, either alone or in combination with other sonographically detectable structural abnormalities, may be a useful parameter in predicting fetal aneuploidy. Copyright © 2002 ISUOG