Position of the conus medullaris in fetuses with skeletal dysplasia

To examine whether reduced conus distance (CD) measurement may be a marker for impaired growth of the fetal trunk in fetuses with certain types of skeletal dysplasia.

Two hundred fifty-four normal cases and 24 pregnancies with skeletal dysplasia were included. The fetuses with skeletal dysplasia were subdivided into two groups based on the specific diagnosis: skeletal dysplasias with a short trunk and skeletal dysplasias with a normal size trunk. Linear regression analysis was used to examine the relationship of the CD measurement with the biparietal diameter. CD measurements in the two groups of fetuses with skeletal dysplasia were compared using z-scores.

In fetuses with skeletal dysplasia and shortened trunk, the CD measurement was significantly smaller than in the normal population (mean z-score -3.7, p < 0.0001). CD measurements in fetuses with skeletal dysplasia but a normal trunk size were similar to the normal population (mean z-score -0.1, p = 0.997).

Short CD is associated with certain types of skeletal dysplasia. As such, measuring the CD may be helpful in diagnosing these conditions.