['Beta-human chorionic gonadotropin (HCG) and pregnancy-associated plasma protein (PAPP-A) are placentally produced proteins whose levels are altered in pregnancies with trisomy 21. PLAC4 is located on chromosome 21 and its expression is restricted to the placenta. Here we investigated whether the levels of beta-HCG-, PAPP-A- and PLAC4 mRNA could be able to discriminate pregnancies whose fetus is affected by trisomy 21.', 'Hundred and forty-three blood samples from normal pregnancies and eight samples from trisomic pregnancies were collected. Total RNA was extracted from whole maternal blood, reverse-transcribed and the three mRNAs were quantified by real-time quantitative PCR. Hundred and nine controls were also tested for the serum levels of PAPP-A and HCG proteins.', 'Beta-HCG and PLAC4 mRNAs were detected in all samples, in higher amounts than in plasma, whereas the detection rate for PAPP-A mRNA was below 10%. The levels of beta-HCG mRNA significantly correlated with the circulatory concentrations of the HCG protein. However, neither beta-HCG- nor PLAC4 mRNAs show a significant difference between cases and controls.'] Are pLAC4 and beta-HCG mRNA levels altered in the maternal circulation of pregnancies with trisomy 21?