Screening for Down syndrome with the femur length/biparietal diameter ratio: a new twist of the data.

Abstract

The purpose of this study was to determine the value of discordant morphometric measurements as identifiers of Down syndrome by evaluating the relationship of biparietal diameter, femur length, biparietal diameter/femur length ratio, and cephalic index between a group of fetuses with trisomy 21 and a control population. Biometric measurements from 48 fetuses with trisomy were reviewed and compared with 107 normal fetuses of similar gestational age. Data were analyzed in 2-week gestational age intervals to determine the effect of gestational age on ultrasonographic detection of Down syndrome. Outcome measures were subject to least-squares linear regression and the t test for analysis. A positive relationship between abnormal morphometric measurements and fetuses with Down syndrome was detected but only during specific weeks of pregnancy. Although it appears that biometric measurements may be useful for Down syndrome, further study is needed before its widespread introduction into clinical practice.