Prenatal Evaluation of the Fetal Conus Medullaris on a Routine Scan.

OBJECTIVE To assess the ability to identify the conus medullaris (CM) and measure the conus-sacrum distance (CS distance) on a routine scan and the relationship with maternal and fetal factors. METHODS This was a prospective study. The assessment of the CM and the CS distance and the influence of the body mass index (BMI), gestational age (GA) and fetal position were analyzed. The correlation between the femur length (FL) and the GA with the CS distance was evaluated. RESULTS A total of 696 fetuses were analyzed. The CM could be visualized in 82.3% of the cases, and the CS distance could be analyzed in 81.2% of the cases. The CM assessment was statistically associated with BMI and fetal position but not with GA. The CS distance assessment was statistically associated with BMI and GA but not with fetal position. We determined a significant association between the FL/CS distance and between the GA/CS distance. CONCLUSIONS Assessment of the CM is possible on most routine scans. The CS distance could be introduced to routine scans for the assessment of prenatal skin-covered spinal dysraphism. High BMI, advanced GA and breech presentation could be potential factors limiting the feasibility of evaluating the CM.