Utility of routine mid-trimester fetal ultrasound scan in detecting filar cysts and follow-up outcomes

Purpose

To assess the value of routine mid-trimester fetal ultrasound scans in detecting FCs, as well as the related ultrasound and clinical follow-up outcomes.

Methods

A retrospective analysis was conducted on 1064 fetuses who underwent standardized ultrasound screening during the mid-trimester. During the examination, high-frequency ultrasound was used to examine the fetal spine. Different frequency ultrasound probes were used to compare and analyze the detection rates of FCs. We conducted follow-up ultrasound observations on all FCs and conducted long-term follow-up observations in terms of the motor function of the children after birth.

Results

Among 1064 fetuses detected by ultrasound, a total of 910 fetuses were completely evaluated using high-frequency and low-frequency ultrasound, and 24 FCs were found. In all 24 cases of FCs, 7 cases were detected using low-frequency ultrasound, while high-frequency ultrasound detected all cases. There was a significant difference in the detection rates between the two groups (χ² = 26.323, P = 0.000). Of all the 24 FCs, 21 cysts disappeared spontaneously (87.5%); one fetus was induced for abortion due to a concurrent cleft lip; after multiple ultrasound examinations, it was found that the cyst persisted in one fetus; one case was not followed up by ultrasound. There was no statistically significant difference in the start of sitting and crawling time between the control group and the FCs group.

Conclusion

Routine mid-trimester fetal ultrasound scan detect FCs, particularly when high-frequency ultrasound probes were routinely applied. Most FCs detected by prenatal ultrasound spontaneously disappear and have no impact on the motor function of the fetus after birth (with the conus medullaris located at or above the L3 level). The shortest time interval from the detection to the disappearance of the cyst was 11 days.