About 33 hours into labour with DS when MWs were talking "failure to progress" and hospital transfer I asked for an enema and one more hour since I could feel DS pushing on my bowels (not effective pressure). OMG, it was night and day. Contractions actually felt GREAT (like they were finally doing something) and it saved me a hospital transfer. The midwives noticed the change in my attitude and my progress and were comfortable giving me more time...he came about 3 hours later.
I have no plans one way or the other for this time around, hopefully I'll naturally clear things out before getting labour started, but if I feel any "blockage" I won't hesitate to ask for one sooner rather than later!