The detection efficacy of noninvasive prenatal genetic testing (NIPT) for sex chromosome abnormalities and copy number variation and its differentiation in pregnant women of different ages

Objective

To analyze the efficacy of noninvasive prenatal genetic testing (NIPT) in detecting fetal sex chromosome abnormalities and copy number variation (CNV), compare the efficacy between NIPT and serological screening alone, and further analyze the fetal sex chromosome abnormalities and CNV differentiation in pregnant women of different ages, so as to provide a reference for the prevention and control of fetal birth defects.

Methods

Clinical data from 22,692 pregnant women admitted to our hospital from January 2013 to December 2022 were retrospectively analyzed. All participants underwent serological screening and NIPT screening to compare fetal chromosomal abnormalities between the two screening modalities. 145 women whose fetus were diagnosed as sex chromosome abnormalities and 36 women whose fetus were diagnosed as CNV abnormalities based on NIPT screening were selected for prenatal diagnosis by amniocentesis or karyotyping. Taking prenatal diagnosis as the standard, the four-grid table method was used to detect the positive predictive value of NIPT screening for fetal sex chromosomal abnormalities and CNV. According to the age, pregnant women were divided into 18-30 years old (n = 9844), 31-35 years old (n = 7612), >35 years old (n = 5236), and then the detection rates of sexual fetal chromosomal abnormalities, CNV and total chromosomal abnormalities were compared in pregnant women.

Results

Among the 22,692 pregnant women in this study, the high-risk proportion of serologic screening with 4.38% was higher than that of NIPT screening with 1.93% (P < 0.05). Among the 145 women with fetal sex chromosome abnormalities screened by NIPT, 122 cases of fetal sex chromosome abnormalities were diagnosed prenatally, including 45, X/47, XXX/47, XYY/47, XXY. The positive predictive values of NIPT screening were 25.00%, 58.82%, 85.71%, and 85.71%, respectively, with an overall predictive value of 44.26%. The positive predictive value of fetal sex chromosome abnormalities in NIPT screening was higher than that of serological screening (P < 0.05). Among the 36 pregnant women with fetal CNV, NIPT screening showed that CNVs≤10 Mb and CNVs>10 Mb were 33.33% and 66.67%, respectively. There were 12 cases of prenatal diagnosis of fetal CNV, among which the NIPT-screened positive predictive values of fetal copy number deletion, duplicate, deletion and duplicate were 50.00%, 57.14% and 100.00%, respectively, with an overall predictive value of 58.33%. The positive predictive value of CNV in NIPT screening was higher than that of serological screening without statistically significant difference (P > 0.05). The results of NIPT screening showed that the detection rate of fetal sex chromosome abnormalities and total abnormalities of pregnant women over 35 years of age was significantly higher than that of pregnant women aged 18-30 and 31-35 years (P < 0.05).

Conclusion

NIPT screening could greatly improve the detection efficacy of fetal sex chromosome abnormalities, CNV and other chromosome abnormalities, and decline the false positive rate. However, the positive predictive value of NIPT screening was relatively low, and further prenatal testing and genetic counseling are still required. In addition, NIPT screening for fetal sex chromosome abnormalities, and the detection rate of total abnormalities in pregnant women older than 35 years old were increased significantly, and pregnancy at an advanced age may be one of the risk factors for fetal chromosomal abnormalities.

Association of chromosomal abnormalities with prenatal exposure to heavy metals: A nested case-control study in high-risk pregnant women in China

Prenatal exposure to heavy metals causes multiple hazards to fetal growth and development. Epidemiological studies on the association between heavy metals and fetal chromosomal abnormalities (CAs) are lacking. We conducted a nested case-control study in a cohort of high-risk pregnant women in China from September 2018 to June 2021. A total of 387 participants were diagnosed with fetal CAs in the case group and 699 were diagnosed with a normal karyotype in the control group. Amniotic fluid concentrations of 10 metals (barium, cobalt, antimony, manganese, ferrum, copper, selenium, strontium, vanadium, and chromium) were measured using inductively coupled plasma-mass spectrometry. We applied quantile g-computation and weighted quantile sum regression to assess the overall effect of metal mixtures and identify metals with significant weight. Logistic and Poisson regression analyses were used to estimate the effects of metals on CAs and CAs subtypes. Our results showed that the metal mixture concentrations were positively associated with the risk of fetal CAs. In adjusted logistic models, Sb was associated with fetal CAs (OR=1.15, 95% CI: 1.02-1.30), and revealed a linear dose-response relationship between Sb level and the risk of fetal CAs. Additionally, the exploratory analysis revealed that Sb levels were associated with Klinefelter syndrome (OR=1.452, 95% CI: 1.063-1.984) and Turner syndrome (OR=1.698; 95% CI,1.048-2.751). Our study revealed that metal mixtures are associated with a higher risk of fetal CAs and that this association may be driven primarily by Sb. Moreover, we provide a genetic perspective on the effects of heavy metals on sexual development in humans.