Fig. 2From: Positive predictive value of non-invasive prenatal screening for fetal chromosome disorders using cell-free DNA in maternal serum: independent clinical experience of a tertiary referral centerMedian and distribution of a maternal age at delivery and b gestational age at NIPS. P-values based on Wilcoxon’s rank sum test (*P < 0.05, **P < 0.01). Abbreviations: NIPS, non-invasive prenatal screeningBack to article page