Clinical analysis of prenatal diagnosis, ultrasound findings, and follow-up in 92 Turner mosaic fetuses: a retrospective analysis of 12-year experience

OBJECTIVE: This study conducted a retrospective analysis on ultrasound findings, karyotype characteristics, pregnancy outcomes, and follow-up data for 92 fetuses diagnosed with Turner mosaicism. It provides essential clinical data on the prenatal and postnatal outcomes of these cases. METHODS: A comprehensive review and analysis were conducted on 92 cases of Turner mosaic fetuses diagnosed by karyotyping, SNP-array, or FISH at the Prenatal Diagnosis Center of Shenzhen Longgang Maternal and Child Health Hospital, a tertiary medical center, between January 2013 and September 2025. The analysis focused on maternal demographic data, types and proportions of mosaic karyotypes, ultrasound findings, pregnancy outcomes, and postnatal follow-up data. RESULTS: Of 12,855 high-risk pregnancies undergoing amniocentesis, 92 Turner mosaic fetuses ( 0.72%, 92/12855) were identified. The majority (65/92, 70.7%) exhibited X-chromosome aneuploidy mosaicism, most commonly 45,X/46,XX (52 cases). Mosaicism involving structural abnormalities of the X chromosome was observed in 27 cases (29.3%), including eight cases of 45,X/46,X, i(X)(q10). Ultrasonography detected abnormalities in 10 fetuses - three with cardiovascular malformations, two with growth restriction, and one with cystic hygroma - while the remaining 82 cases had no abnormal ultrasound findings. Two cases were notable for complex multi-system anomalies: one with 45,X[24]/46,XX[76] presented with coarctation of the aorta, a horseshoe kidney, and increased nuchal translucency (3.2 mm); another with 46,X, i(X)(q10)[66]/46,XX[24] had a ventricular septal defect, left clubfoot, and bilateral ventricular widening. Of the 92 fetuses with Turner mosaicism, 69 pregnancies were terminated and 23 were continued. Among the 23 continuing pregnancies, one resulted in embryonic arrest, one was subsequently terminated, and one delivered preterm at 34 weeks. Twenty infants were live-born and followed up: three showed delayed language and motor development, one had epilepsy, one had hearing loss, and one exhibited short stature with dry skin. Notably, the abnormal mosaic ratio in all cases with postnatal findings ranged from 20% to 30%. CONCLUSION: The prenatal phenotype of Turner mosaicism is largely determined by the proportion of abnormal cells and the tissues involved. Clinical decisions should caution against termination for mosaic ratio below 30%, as cases under 10% typically have favorable outcomes. Although prenatal ultrasound findings for Turner mosaicism lack specificity, they may be closely associated with cardiovascular abnormalities and intrauterine growth restriction. After birth, it is crucial to conduct close postnatal monitoring of neurodevelopment for these children.