Objective:To investigate the prenatal ultrasound detection and prognosis of fetuses with cysts of filum terminale.Methods:A retrospective analysis was conducted on 68 fetuses with cysts of filum terminale that underwent level Ⅲ systematic ultrasound examination and were successfully followed up at the Third Affiliated Hospital of Zhengzhou University from January 2020 to June 2023. The analysis included the initial detection time, cyst size, accompanying abnormalities, whether the cysts disappeared in utero, outcomes, and postnatal follow-up. Descriptive statistical analysis was performed.Results:The earliest ultrasound detection of filum terminale cysts was at 21 weeks and 4 days of gestation, with a median length of 4.3 mm (range 2.0-19.5 mm). Among the 68 cases, 69% (47/68) were isolated filum terminale cysts, and 31% (21/68) were non-isolated filum terminale cysts. Structural abnormalities associated with non-isolated filum terminale cysts were most commonly cardiovascular (7/21, 33%), urogenital (6/21, 29%), and neurological (6/21, 29%) systems. Prenatal ultrasound follow-up was performed in 41 cases, with an intrauterine disappearance rate of 63% (26/41). The disappearance rates for isolated and non-isolated filum terminale cysts were 67% (22/33) and 4/8, respectively. The earliest disappearance was at 25 weeks of gestation, with the shortest duration being 12 days. Prenatal genetic testing was conducted in 10 cases, with no definite pathogenic variants detected. There were 10 cases of induced labor, including two cases of isolated filum terminale cysts and eight cases of non-isolated filum terminale cysts. The remaining 58 cases resulted in live births, with postnatal follow-up ranging from 3 months to 3 years, showing no abnormal findings.Conclusion:Most fetal cysts of filum terminale are isolated and can spontaneously disappear in utero, with a generally good prognosis.