EP09.99: Prenatal diagnosis and clinical pregnancy outcome of fetuses with conotruncal defects in a Chinese cohort

This study aimed to explore the genetic etiologies of conotruncal defects (CTDs) in fetuses by analysing the results of different genetic tests and to assess the pregnancy outcomes of fetuses with CTD in a Chinese prenatal cohort. A total of 146 fetuses who underwent invasive prenatal genetic testing for CTD in the prenatal diagnosis centre of the International Peace Maternity and Child Health Hospital between January 2018 and December 2022 were retrospectively analysed. All of them underwent chromosomal microarray analysis (CMA) and karyotype analysis, but only 27 underwent whole-exome sequencing (WES) simultaneously. The results of these different genetic testing methods were collected and compared. Data on pregnancy outcomes and neonate prognosis were obtained from the electronic medical records and postpartum telephone follow-up. In the 146 fetuses with CTD, the chromosome abnormality rate was 22.6% (33/146), and the detection rate of abnormal chromosomes in CMA and karyotype was 15.8% (23/146). Among the twenty-seven pregnant women who accepted WES, five had pathogenic variants, five had likely pathogenic variants, and four had variants of uncertain significance. Copy number variations (CNVs) were identified, and the incremental detection rate was 37.0% (10/27). The detection rate of abnormal chromosomes by CMA was higher in infants with an interrupted aortic arch (IAA) than in the other infant groups (60.0%, χ2 = 11.661, P = 0.045, chi-square test or Fisher's exact test). CTD is a complex congenital heart disease with an etiology closely related to genetic abnormalities. Therefore, invasive prenatal genetic testing and CMA are recommended as first-line tests for all patients with CTD detected by prenatal ultrasound, especially IAA. WES should be recommended when necessary.