Cell-free DNA screening positive for monosomy X: clinical evaluation and management of suspected maternal or fetal Turner syndrome

Incidental finding of maternal sex chromosome aneuploidy from DMD carrier screening and single-nucleotide polymorphism (SNP)-based prenatal cell-free DNA screening

Prenatal cell-free DNA (cfDNA) screening and carrier screening (CS) may have incidental findings that have implications for maternal health outside the scope of the test. We investigated outcome information for individuals with both a DMD full gene deletion/duplication on CS and a suspected maternal X chromosome abnormality on SNP-based prenatal cfDNA screening. This retrospective analysis included de-identified data from pregnant individuals referred for CS and prenatal cfDNA screening at a single reference laboratory (9/2019-12/2021). Maternal karyotype and/or chromosomal microarray analysis results were requested from referring clinics for individuals with both DMD full gene deletion/duplication on CS and prenatal cfDNA screening results indicating potential maternal X chromosome aneuploidy. Of 333,814 individuals screened, 144 (1 in 2318) met study criteria, and for 84 (58.3%) we obtained information on whether diagnostic testing was received following these results. Of the 84 patients with follow-up information available, 34 (40.5%) received maternal diagnostic testing based on karyotype or chromosomal microarray analysis. At 97% (n = 33), the majority of patients with diagnostic testing had X chromosome aneuploidies, including trisomy X (n = 22, 64.7%), monosomy X mosaicism (n = 8, 24.2%), monosomy X (n = 2, 6.1%), and maternal X chromosome structural abnormality (n = 1, 2.9%). Our study supports a high likelihood of maternal sex chromosome abnormality in the presence of an inconclusive DMD result on CS and prenatal cfDNA screening suspicious for a maternal sex chromosome abnormality. Given the implications for maternal health, follow-up counseling, karyotype, and chromosomal microarray analysis may be recommended.

Best Practice & Research clinical obstetrics & gynaecology

Screening for fetal genetic disorders is a focus of prenatal care. Cell free DNA (cfDNA) screening for aneuploidies became available in 2011. Initially available only to high-risk individuals, this test is now standard of care in many settings. cfDNA screening has expanded to include sex chromosomal aneuploidies, copy number variants, and rare autosomal trisomies. However, the positive predictive value for rarer conditions is significantly lower, the number of conditions tested for is small, and abnormal results may occur due to maternal genetic findings. The field is changing quickly, and national recommendations for the use of cfDNA in screening for fetal and maternal diseases varies internationally. Research on the performance of screening for many different genetic disorders using cfDNA is ongoing, and suggests that this methodology may allow for testing of a much greater number of genetic conditions. Additionally, improved understanding of the cfDNA molecules themselves may provide additional insights: both high and low fetal fractions may suggest adverse pregnancy outcomes, and characteristics of the fragments themselves may help distinguish tissue of origin.

Prevalence, diagnostic features, and medical outcomes of females with Turner syndrome with a trisomy X cell line (45,X/47,XXX): Results from the InsighTS Registry

Turner syndrome (TS) is defined by partial or complete absence of a sex chromosome. Little is known about the phenotype of individuals with TS mosaic with trisomy X (45,X/47,XXX or 45,X/46,XX/47,XXX) (~3% of TS). We compared the diagnostic, perinatal, medical, and neurodevelopmental comorbidities of mosaic 45,X/47,XXX (n = 35, 9.4%) with nonmosaic 45,X (n = 142) and mosaic 45,X/46,XX (n = 66). Females with 45,X/47,XXX had fewer neonatal concerns and lower prevalence of several TS-related diagnoses compared with 45,X; however the prevalence of neurodevelopmental and psychiatric diagnoses were not different. Compared to females with 45,X/46,XX, the 45,X/47,XXX group was significantly more likely to have structural renal anomalies (18% vs. 3%; p = 0.03). They were twice as likely to have congenital heart disease (32% vs. 15%, p = 0.08) and less likely to experience spontaneous menarche (46% vs. 75% of those over age 10, p = 0.06), although not statistically significant. Congenital anomalies, hypertension, and hearing loss were primarily attributable to a higher proportion of 45,X cells, while preserved ovarian function was most associated with a higher proportion of 46,XX cells. In this large TS cohort, 45,X/47,XXX was more common than previously reported, individuals were phenotypically less affected than those with 45,X, but did have trends for several more TS-related diagnoses than individuals with 45,X/46,XX.

Assessment of obstetric characteristics and outcomes associated with pregnancy with Turner syndrome

OBJECTIVE

To assess national-level trends, characteristics, and outcomes of pregnancies with Turner syndrome in the United States.

DESIGN

Cross-sectional study.

SETTING

The Healthcare Cost and Utilization Project's National Inpatient Sample.

SUBJECTS

A total of 17,865,495 hospital deliveries from 2016-2020.

EXPOSURE

A diagnosis of Turner syndrome, identified according to the World Health Organization's International Classification of Disease 10th revision code of Q96.

MAIN OUTCOME MEASURES

Obstetrics outcomes related to Turner syndrome, assessed with inverse probability of treatment weighting cohort and multivariable binary logistic regression modeling.

RESULTS

The prevalence of pregnant patients with Turner syndrome was 7.0 per 100,000 deliveries (one in 14,235). The number of hospital deliveries with patients who have a diagnosis of Turner syndrome increased from 5.0 to 11.7 per 100,000 deliveries during the study period (adjusted-odds ratio [aOR] for 2020 vs. 2016; 2.18, 95% confidence interval [CI] 1.83-2.60). Pregnant patients with Turner syndrome were more likely to have a diagnosis of pregestational hypertension (4.8% vs. 2.8%; aOR 1.65; 95% CI 1.26-2.15), uterine anomaly (1.6% vs. 0.4%; aOR, 3.01; 95% CI 1.93-4.69), and prior pregnancy losses (1.6% vs. 0.3%; aOR 4.70; 95% CI 3.01-7.32) compared with those without Turner syndrome. For the index obstetric characteristics, Turner syndrome was associated with an increased risk of intrauterine fetal demise (10.9% vs. 0.7%; aOR 8.40; 95% CI 5.30-13.30), intrauterine growth restriction (8.5% vs. 3.5%; aOR 2.11; 95% CI 1.48-2.99), and placenta accreta spectrum (aOR 3.63; 95% CI 1.20-10.97). For delivery outcome, pregnant patients with Turner syndrome were more likely to undergo cesarean delivery (41.6% vs. 32.3%; aOR 1.53; 95% CI 1.26-1.87). Moreover, the odds of periviable delivery (22-25 weeks: 6.1% vs. 0.4%; aOR 5.88; 95% CI 3.47-9.98) and previable delivery (<22 weeks: 3.3% vs. 0.3%; aOR 2.87; 95% CI 1.45-5.69) were increased compared with those without Turner syndrome.

CONCLUSIONS

The results of contemporaneous, nationwide assessment in the United States suggest that although pregnancy with Turner syndrome is uncommon this may represent a high-risk group, particularly for intrauterine fetal demise and periviable delivery. Establishing a society-based approach for preconception counseling and antenatal follow-up would be clinically compelling.

Clinical practice guidelines for the care of girls and women with Turner syndrome

Turner syndrome (TS) affects 50 per 100 000 females. TS affects multiple organs through all stages of life, necessitating multidisciplinary care. This guideline extends previous ones and includes important new advances, within diagnostics and genetics, estrogen treatment, fertility, co-morbidities, and neurocognition and neuropsychology. Exploratory meetings were held in 2021 in Europe and United States culminating with a consensus meeting in Aarhus, Denmark in June 2023. Prior to this, eight groups addressed important areas in TS care: (1) diagnosis and genetics, (2) growth, (3) puberty and estrogen treatment, (4) cardiovascular health, (5) transition, (6) fertility assessment, monitoring, and counselling, (7) health surveillance for comorbidities throughout the lifespan, and (8) neurocognition and its implications for mental health and well-being. Each group produced proposals for the present guidelines, which were meticulously discussed by the entire group. Four pertinent questions were submitted for formal GRADE (Grading of Recommendations, Assessment, Development and Evaluation) evaluation with systematic review of the literature. The guidelines project was initiated by the European Society for Endocrinology and the Pediatric Endocrine Society, in collaboration with members from the European Society for Pediatric Endocrinology, the European Society of Human Reproduction and Embryology, the European Reference Network on Rare Endocrine Conditions, the Society for Endocrinology, and the European Society of Cardiology, Japanese Society for Pediatric Endocrinology, Australia and New Zealand Society for Pediatric Endocrinology and Diabetes, Latin American Society for Pediatric Endocrinology, Arab Society for Pediatric Endocrinology and Diabetes, and the Asia Pacific Pediatric Endocrine Society. Advocacy groups appointed representatives for pre-meeting discussions and the consensus meeting.

Chorionic Villous Testing Versus Amniocentesis After Abnormal Noninvasive Prenatal Testing

In the setting of a normal first-trimester ultrasound, an amniocentesis may be a better option than chorionic villous sampling for invasive diagnostic testing after a cell-free DNA high risk for trisomy 13, given the high rates of confined placental mosaicism. In unaffected fetuses, other evaluations should be considered depending on the cell-free DNA results, including maternal karyotyping for monosomy X, uniparental disomy testing for chromosomes with imprinted genes, serial growth scans for trisomy 16, and a workup for maternal malignancy for multiple aneuploidies or autosomal monosomy.

Multicenter clinical experience with non-invasive cell-free DNA screening for monosomy X and related X-chromosome variants

OBJECTIVE

We aimed to investigate how the presence of fetal anomalies and different X chromosome variants influences Cell-free DNA (cfDNA) screening results for monosomy X.

METHODS

From a multicenter retrospective survey on 673 pregnancies with prenatally suspected or confirmed Turner syndrome, we analyzed the subgroup for which prenatal cfDNA screening and karyotype results were available. A cfDNA screening result was defined as true positive (TP) when confirmatory testing showed 45,X or an X-chromosome variant.

RESULTS

We had cfDNA results, karyotype, and phenotype data for 55 pregnancies. cfDNA results were high risk for monosomy X in 48/55, of which 23 were TP and 25 were false positive (FP). 32/48 high-risk cfDNA cases did not show fetal anomalies. Of these, 7 were TP. All were X-chromosome variants. All 16 fetuses with high-risk cfDNA result and ultrasound anomalies were TP. Of fetuses with abnormalities, those with 45,X more often had fetal hydrops/cystic hygroma, whereas those with "variant" karyotypes had different anomalies.

CONCLUSION

Both, 45,X or X-chromosome variants can be detected after a high-risk cfDNA result for monosomy X. When there are fetal anomalies, the result is more likely a TP. In the absence of fetal anomalies, it is most often an FP or X-chromosome variant.