http://www.betterhealth.vic.gov.au/bhcv2/bhcmed.nsf/pages/csccervi/$File/csccervi.pdf
Ingredients:
Pessary (vaginal insert)
The active ingredient in CERVIDIL® is dinoprostone.
The active ingredient is within a plastic (polyurethane) sustained release insert which contains:
hexanetriol/macrogol 8000/isocyanate cross-linked hydrogel copolymer.
The insert is held within a pouch in continuity with a withdrawal tape.
Pouch and tape are made of knitted polyester yarn.

I can't find a single reference for where the prostaglandin E2 is made from - and that includes pigs. I would be reticent to believe an inflamatory webpage like the one your info is from. Obviously, there is prostaglandin E2 in semen of pigs - but it's also in donkeys, rats, dogs, humans, rainbow trout, etc... I think you get my point.

The only reference for pig (boar, actually) semen & prostaglandin E2 I found was in a paper on improving artificial insemination of pigs.

In terms of disease risk - I'd rather pig semen than human semen.