Application of single nucleotide polymorphism array in prenatal diagnosis for fetuses with abnormal ultrasound findings

Objective To investigate the value of single nucleotide polymorphism array (SNP-array) for fetuses with abnormal ultrasound findings. Method A total of 904 fetuses with abnormal ultrasound findings were enrolled in this study from May 2015 to November 2017, and 434 (48.0%) cases received conventional karyotyping analysis at the same time. According to different abnormal ultrasound category, 904 cases were divided into 5 groups: 280 cases (31.0%) in single system structural anomalies, 31 cases (3.4%) in multiple system structural anomalies, 331 cases (36.6%) in single ultrasound soft marker abnormalities without structural anomalies, 107 cases (11.8%) in multiple soft marker abnormalities and 155 cases (17.2%) in structural abnormalities combined with soft markers abnormalities. Abnormal detection rates by SNP-array among 5 groups of abnormal ultrasound category were calculated. Result (1) Total SNP-array results: 171 (19.0%) cases out of 904 cases analyzed by SNP-array, presented chromosomal abnormalities. Pathogenic copy number variants were detected in 27 cases (3.0%) and variants of unknown significance were detected in 81 cases (7.8%) . In addition, 7 cases (26.0%) were found with new mutation by parental validation. (2) SNP-array of 5 groups: among the 5 groups of abnormal ultrasound category, chromosomal abnormalities were identified by SNP-array in 19.3% (54/280) with single system structural abnormalities, 25.8% (8/31) with multiple system structural abnormalities, 13.9% (46/331) with single nonstructural anomalies, 19.6% (21/107) with multiple nonstructural anomalies and 27.1% (42/155) with structural abnormalities combined with nonstructural anomalies. The differences were significant (P=0.010) . No chromosome abnormalities was identified in single soft marker abnormalities, such as choroid plexus cysts, echogenic foci in the heart, single umbilical artery and pyelectasis. (3) Chromosomal abnormalities: the abnormal detection rate of aneuploidy chromosomal abnormalities by SNP-array increased with the maternal age, decreased with the gestational weeks (all P 0.05) . (4) SNP-array and karyotyping: 434 cases were analyzed by conventional karyotyping and SNP-array respectively, 10.3% (43/419) of which presented chromosomal abnormalities by conventional karyotyping and 18.7% (81/434) of which presented chromosomal abnormalities by SNP-array. Conclusions SNP-array could be a useful genetic analysis method in prenatal diagnosis for fetuses with abnormal ultrasound findings. For different abnormal ultrasound category, SNP-array has different detection rate. Compared with conventional karyotyping analysis, SNP-array can improve the detection rates for chromosomal abnormalities and find the chromosome abnormalities which can′t be detected by conventional karyotyping analysis. In clinical prenatal genetic counseling, SNP-array should be selected rationally in combination with the various abnormal ultrasound category. Key words: Congenital abnormalities; Chromosome aberrations; Polymorphism, single nucleotide; Karyotyping; Ultrasonography, prenatal