Only anecdotal info here.  Prostaglandin gel was used in my labor when I
had been having strong contractions (for hours and hours and hours and...)
that didn't serve to dialate (sp?) my cervix at all.  My understading was
that the gel was supposed to help the contractions be more productive.  The
result was that it did absolutely nothing - the contractions didn't change
and (unfortunately) neither did my cervix.  (Of course, eventually the
cervix did change and [surprise!] I had a baby!  ;-))

Linda V.