Evidence that the PR isoform in human fetal membranes and placenta at term is either PR-C or PR-M. RT-PCR products generated from fetal membrane samples that had decidua attached (FM + dec) or fetal membranes that had the decidua scraped away (FM – dec) or term placenta (Plac). One μg of DNase-treated total RNA was reverse transcribed in the presence (+), or absence (-), of AMV-RT. Both samples were then amplified in a PCR with isoform-specific primers (see Table 1) that detected all known PR isoforms; the PR-B isoform alone; a combination of PR-A and PR-B; or the PR-S isoform alone. GAPDH was used a control for efficiency of mRNA manipulation and PCR amplification. Myometrium (myo) was used as a positive control for PR with T47D cell extract as a positive control for PR-S (separate column), and in all cases a minus RT sample was incorporated to rule out the presence of contaminating genomic DNA. Results are representative of four independent assessments. Data show the presence of PR in all 4 tissue samples and T47D cells.