RT-PCR gels showing the PR transcripts found in extracts of enriched amnion (amnion), chorion (chorion) and decidua (decidua). Data were obtained from the +RT sample only and indicate that the amnion contains a PR transcript that is not PR-A or PR-B. Additionally, enriched decidua contains the PR-S isoform whereas the chorion (which is contaminated with decidua) also contains PR-S, PR-B and PR-A. The amnion does not contain these transcripts, but does contain a PR isoform. The bands visible at the bottom of the 186 bp PR-S isoform gel are unused primers.