Prenatal diagnosis and pregnancy outcomes in high-risk and borderline high-risk pregnant women for Down syndrome

Abstract

Background: Non-invasive prenatal testing (NIPT) and serological triple screening were used to analyse the clinical and pregnancy outcomes of women classified as borderline/high-risk for Down syndrome (DS). Results: A retrospective analysis was conducted on 3,245 pregnant women who underwent karyotyping combined with BACs-on-Beads^TM (BoBs^TM) and karyotyping combined with chromosomal microarray analysis (CMA). The overall prevalence of fetuses at high risk of DS was 7.55% (245/3245), of which the incidence of DS was 84.49% (207/245), sex chromosome aneuploidy (SCA) was 5.31% (13/245), trisomy 18 was 4.49% (11/245), pathogenic copy number variations (PCNVs) was 4.08% (10/245), and variant of uncertain significance (VOUS) was 1.22% (3/245). Seven cases of mosaicism undetected by BoBs^TM and one case of mosaicism undetected by CMA were detected by karyotyping. One additional complex rearrangement was detected by karyotyping. The CNV detection rate of CMA was higher than that of BoBs^TM [1.75% (9/513) vs. 0.15% (4/2732)]. The positive predictive values of NIPT (70.00%) were higher than those of serological triple screening (0.95%), which is useful in DS, trisomy 18, SCA, and CNV. Of the pregnancies, 96.62% (200/207) were DS; 100% (11/11), trisomy 18; 61.54% (8/13), SCA; 70.00% (7/10), PCNVs; and 0% (0/3), VOUS terminated pregnancies. Conclusions: Serological triple screening is useful for DS and SCA, trisomy 18, and CNV. Karyotyping combined with CMA detected more mosaicism and CNV than karyotyping combined with BoBs^TM. The labour induction rate of DS and trisomy 18 was higher than that of SCA, and PCNVs were higher than VOUS.