cfDNA accuracy for prenatal detection of sex chromosome aneuploidy. Data are presented as author (year) with calculated sensitivity and specificity displayed as point estimates with 95% confidence intervals. Forest plots for sensitivity and specificity are included for 45,X (A,B), 47,XXY (C,D), 47,XXX (E,F) and 47,XYY(G,H). The overall estimated pooled summary statistic. I^2 = variation in the estimated pooled sensitivity or specificity attributable to heterogeneity.