The Importance of Prenatal WES Testing in the Romanian Population

Objective: Our objective was to observe the benefits and limitations of WES (Whole Exome Sequencing) in the prenatal setting, in the Romanian population. The scope was to observe the diagnostic yield in comparison to molecular karyotyping testing, which had negative results, as well as a case of consanguinity. Methods The first criteria was selecting pregnancies with abnormal ultrasound findings. These findings would not lead the medical team to a certain known syndrome. Second, we performed SNP-array, which tested negative in all cases, except for Case number 9 which had an abnormal result. The ulterior testing method was WES, using Massive Parallel Sequencing of the whole coding region of the human genome on Next Generation Sequencing Platform, NovaSeq 6000 (average coverage >100X, read length: 2x100bp). The Twist Human Core Exome kit RefSeq & Mitochondrial panel (Twist Bioscience) was used for the library preparation. Bioinformatic analysis was performed by direct comparison of the genome of the test sample with the human reference sequence (hg38). Results Our small cohort of 10 patients, resulted in a 50% diagnostic yield. After receiving the results whether a diagnose or a negative result, 2 couples chose to terminate the pregnancy, 5 were born affirmatively without symptoms, and are still monitored up to date. One of the pregnancies led to a stillbirth. We have also found 3 incidental findings that helped the multidisciplinary team better manage the patient as well as the members at risk. Conclusion In this article we present 10 cases which were tested through prenatal WES, showing the great diagnostic yield in comparison to SNP-array in our selected cases. As a closing remark, we wish to highlight the benefits of WES testing in prenatal cases. Further testing is needed to get a clearer picture of the prenatal diagnostic yield in the Romanian population.