[Genetic analysis of 74 fetuses terminated for skeletal dysplasia and evaluation of diagnostic performance of whole exome sequencing].

Objective: To explore the genetic etiology of fetal skeletal dysplasia using whole exome sequencing (WES) and copy number variation sequencing (CNV-seq) techniques, and the feasibility of using WES as the first-tier method for such fetuses.

Methods: Seventy four fetuses with skeletal dysplasia detected by prenatal ultrasound at the Genetic Testing Center of the Women and Children's Hospital Affiliated to Qingdao University from January 2020 to August 2024 were selected as the study subjects. Fetal muscle and peripheral blood samples of the pregnant women and their spouses were collected and subjected to WES analysis. CNV-seq was carried out on all fetal muscle tissue samples. And the results were compared with the CNVs indicated by WES. Genetic etiologies were analyzed across different subtypes of skeletal dysplasia. And the feasibility of using WES as the first-tier genetic test for similar fetuses was assessed, in addition with a systematic cost-effectiveness analysis. This study was approved by the Medical Ethics Committee of the Hospital (Ethics No.: QFELL-YJ-2024-201).

Results: A total of 50 fetuses were diagnosed, which yielded a diagnostic rate of 67.57%. These included 6 chromosomal aneuploidies, 4 chromosomal CNVs and 40 monogenic disorders. The monogenic diseases had involved 46 variant sites in 23 pathogenic genes, among which 12 were unreported previously, including MYH3: c.735T>C, ALPL: c.1324C>T, NEK9: c.1973G>A, MAGEL2: c.2024_2025del, LMBR1: c.423+4914A>C, NEB: c.21273_21276del, COL1A1: c.2651G>C and c.2758G>C, ASPM: c.2473delinsGA, TBX5: c.704G>A, DYNC2H1: c.10893del, and DYNC2I2: c.1270C>T. Substantial concordance was reached between WES-derived CNV calls and CNV-seq findings. No clinically significant CNV was exclusively detected by CNV-seq. Cost-effectiveness modeling demonstrated that implementing WES as the first-tier genetic testing method could reduce the total expenditure when WES unit cost remained below 6.4 folds that of the CNV-seq.

Conclusion: Genetic variants including single nucleotide variations (SNV) of monogenic disorders, chromosomal aneuploidies and genomic CNVs are important causes for fetal skeletal dysplasia. WES is an accurate and efficient method for analyzing the etiology of fetal skeletal dysplasia, particularly in those with a family history of similar phenotype or maternal history of adverse pregnancies.