Cell-free DNA screening for sex chromosome aneuploidy in 67,099 pregnancies: A retrospective analysis.

ObjectivesTo evaluate the efficacy of non-invasive prenatal testing in detecting sex chromosome aneuploidies.MethodsA total of 67,099 pregnant women were recruited in this retrospective observational study at Peking Union Medical College Hospital; 300 cases at high risk of sex chromosome aneuploidies were screened and 36 cases refused invasive prenatal diagnosis after detailed prenatal genetic counselling. The clinical data and prenatal diagnosis results were collected.Results101 cases were in accordance with non-invasive prenatal testing results after invasive prenatal diagnosis: 95 cases had follow-up confirmation with abnormal sex aneuploidies (14 for monosomy X; 36 for 47, XXY; 22 for trisomy X and 23 for 47, XYY). The total positive predictive value was 38.26% (101/264). The accuracy of different Z scores was calculated, respectively, with positive predictive value ranging from 33.96% to 41.38% and a decreased sensitivity with rise of the Z score.ConclusionsNon-invasive prenatal testing is an effective screening method for sex chromosome trisomy, rather than monosomy X, with relatively high accuracy. Z score = 3 is an optimum risk threshold in sex chromosome aneuploidies.