FETAL EAR MEASUREMENTS IN THE PRENATAL DETECTION OF TRISOMY-21

Although prominent fetal nuchal folds, short long bones, echogenic bow el, and renal pelviectasis have been shown to be associated with triso my 21, none has acceptable diagnostic efficacy. Diminished fetal ear l engths measured by ultrasound have recently been reported as yet anoth er potential morphological marker for the prenatal detection of trisom y 21. To investigate this further, we measured ear lengths and widths of normal (n=107) and trisomy 21 (n=25) second-trimester formalin-pres erved fetuses. The normal ear growth characteristics are described and compared with those of trisomy 21 fetuses. The normal fetal ear shape , not unlike that of the neonates, manifested a marked variation. When the ear lengths and widths were regressed against gestational age, th e slopes of the regression lines for the two groups were found to be d ifferent (P<0.001). However, despite the statistically significant dif ference between the ear sizes of normal and trisomy 21 fetuses, the wi de range of normal variation seen at each gestational age means that t he fetal ear measurements are not diagnostically helpful.