Clin Obstet Gynecol. 2023 Sep 1;66(3):568-578. doi: 10.1097/GRF.0000000000000804. Epub 2023 Jul 24. ABSTRACT Noninvasive prenatal testing (NIPT) for the sex chromosome aneuploidies (45,X, 47,XXY, 47,XXX, and 47,XYY) differs significantly from that for the autosomal aneuploidies (trisomy 13, 18, and 21). As a group, sex chromosome aneuploidies occur more commonly (1/400) than any one isolated autosomal aneuploidy, the phenotypic variation is greater, the role of mosaicism more challenging, and the positive predictive value of a high-risk NIPT result is substantially lower. These considerations should be identified during pretest counseling, the inclusion of sex chromosome testing offered separately, and the differences from autosomal aneuploidy NIPT clearly delineated. PMID:37650669 DOI:10.1097/GRF.0000000000000804