Explore the dynamic alternation of gene PLAC4 mRNA expression levels in maternal plasma in second trimester for nonivasive detection of trisomy 21

Objective Noninvasive prenatal detection of trisomy 21 (T21) has been achieved by measuring the ratio of two alleles of a single nucleotide polymorphism in circulating placenta specific 4 (PLAC4) mRNA in maternal plasma with a few assays in recent years. Our research is to explore the variations of PLAC4 mRNA expression level in maternal plasma with normal pregnancies in second trimester, which can provide pregnant women deeper insights with suitable detection period for the non-invasive prenatal detection of T21.