Analysis of genetic abnormalities and clinical outcome of fetus with ultrasonic nonstructural abnormality

Objective: To analysis the incidence of abnormal genetics and the clinical outcome of fetuses with ultrasonic nonstructural abnormality. Methods: This study was conducted retrospectively. 631 pregnant women were enrolled in the Prenatal Diagnostic Center of Fujian Maternal and Child Health Hospital due to ultrasonic nonstructural abnormality from January 2016 to January 2019. According to different gestational weeks, amniotic fluid or umbilical cord blood samples were collected for chromosome karyotype analysis and SNP-array. According to the number of nostructural abnormalities, they were divided into 1 nostructural abnormality group, 2 nostructural abnormalities group, and ≥3 nostructural abnormalities group. Chi-square test was used for comparison between groups. Results: Of the 631 cases, 34 cases (5.4%, 34/631) had abnormal karyotypes, including 20 cases with abnormal chromosome number and 14 cases with abnormal chromosome structure. In results of SNP-array, there were 53 abnormal results (8.4%, 53/631), including 32 cases of pathogenic copy number variations (CNV) and 21 cases of variations of uncertain clinical significance (VOUS). The rates of pathogenic CNV were 4.57% (21/260), 4.76% (7/147) and 16.67% (4/24) in the group of 1, 2 and ≥3 nostructural abnormalities, respectively. The rate of the three groups showed a linear trend, and the difference was statistically significant (χ²=7.419,P<0.05). In the single nostructural abnormality group, the rate of pathogenic CNV of nasal bone dysplasia, fetal growth restriction (FGR) and thickened nuchal translucency (NT) were 8.11% (3/37), 7.04% (5/71) and 5.60% (7/125), respectively. Conclusions: Compared with the karyotype analysis, SNP-array can significantly improve the detection rate of genetic abnormalities in ultrasonic nonstructural abnormality. When multiple ultrasonic nonstructural abnormality were combined, the risk of genetic abnormalities showed an upward trend.