Prenatal diagnosis of fetal skeletal anomalies via whole-exome sequencing in a tertiary referral center

Abstract

Abstract The accurate prenatal diagnosis of skeletal anomaly (SKA) using prenatal imaging alone remains challenging. We aimed to investigate the efficacy of whole-exome sequencing (WES) in the prenatal molecular genetic diagnosis of skeletal system abnormalities, with or without additional ultrasound anomalies. All fetuses with SKA were subjected to sequential genetic tests, and after excluding fetal chromosomal abnormalities and clinically significant copy number variations (CNVs) consistent with the observed phenotype, the affected fetuses were further subjected to WES. The clinical features of fetal SKA were collected, and the results of molecular genetic testing and perinatal outcomes were analyzed. Following negative routine genetic test results of the 78 fetuses, trio-WES was conducted for 73 fetuses, and fetus-only WES (single WES) was performed for five fetuses due to parental refusal. Fetal skeletal system abnormalities in our cohort were subdivided into seven groups: 39 (50%) had short long bones, 14 (17.9%) had abnormal limb morphology, 4 (5.1%) had polydactyly, 4 (5.1%) had the absence of the radius tibia or tibiofibula, 5 (6.4%) had spine anomalies, 6 (7.7%) had strephenopodia, and 6 (7.7%) had multiple deformities. In total, we identified the molecular diagnoses for 32/78 fetuses with SKAs, and confirmed 41 pathogenic/likely pathogenic variants in 28 genes, including nine novel variants in our cohort. The overall diagnostic rate was 41% (32/78). Our findings demonstrate that WES can greatly improve the genetic diagnostic rate of fetal SKAs following routine genetic testing, which can comprehensively guide perinatal management and help assess the risk of recurrence in future pregnancies. Our data also provide a basis for the association between the SKA phenotype and related genotypes and expand the spectrum of fetal SKA phenotypes and related genes.

Keywords

• Whole-exome sequencing
• Prenatal diagnosis
• Skeletal anomaly
• TBX6
• Maternal uniparental disomy of chromosome 6