What Constitutes "Intervention" in Birth?

I had a really interesting conversation with a friend recently. She and I each had babies at home this last year. I was attended by a midwife, she gave birth unassisted (without a midwife). We were talking about why I chose to have a midwife, and discussing some of the things that happened during Eagle's birth. I mentioned when he became stuck, and my midwife reached out to work him loose. I (and my midwife I think) thought it was shoulder distocia, and thus felt that it was necessary for her to do something. As it turns out it was not shoulder distocia, but just a very short cord, which soon broke on its own and he came on out without assistance.
My friend said something about my midwife's putting her hands on him having been an unnecessary intervention. This raised a very interesting question for me--is having someone else catch the baby an 'intervention'? Sure, the baby doesn't have to be caught--he could slip out into the water or onto the bed (or onto the floor...it happens!) but isn't it gentler to be received into warm hands as he emerges? I suppose it is technically 'intervening' to cut the umbilical cord too, but even wild animals bite the cord to break it after the baby is born, don't they? How about using props for labor? A pool, a birth ball, a birthing stool--are those interventions? I think one could make the argument that something like a birthing stool 'intervenes' because it helps the mother maintain a position that she could probably not hold for long on her own...on the other hand, I don't think anyone would argue that it's a bad intervention. After all, being able to maintain an upright position can speed the progress of labor, and squatting shortens the birth canal which facilitates birth.

The Mother-Friendly Childbirth Initiative defines intervention as any "practices and procedures that are unsupported by scientific evidence." I don't exactly agree with that definition, as I'm more inclined to to agree with the dictionary and define intervention as "interfering with the outcome or course especially of a condition or process (as to prevent harm or improve functioning)." Intervention means interfering with the outcome or process, which obviously can be a bad thing; but sometimes something goes wrong and intervening is necessary, and not all such interventions are "unsupported by scientific evidence," but they are still interventions by definition because they change the condition or process.

So where does one draw the line? What constitutes 'help' (a good intervention) and what constitutes 'interference' (bad intervention)? I had never thought about this from this angle before, but it's a meaty topic. After all, I might see something as interference, but someone else (be it a mother or a provider) might see it as helpful. Take induction for example--I would avoid labor induction in all but the most extreme situations (and being 42weeks pregnant does not constitute an extreme situation in my book), but I know women who feel that they need medical assistance to go into labor. Obviously what I view as interference is an appreciated help in their eyes. On the other side, some women believe that having any birth professional present will interfere with their ability to birth ideally, and others practice lotus birth, and would view my cord cutting as interference. So I don't think it's easy--maybe not even possible--to draw a definitive line.

I believe that interventions--even big interventions such as epidurals or cesarean sections--definitely have a place. I had AROM (artificial rupture of membranes, aka my "water broken") when Bear was born. We discussed it and felt that it was a good idea considering the circumstances at the time. My water broke on its own minutes before Eagle's birth, which was nice, but I certainly don't think it was bad that we chose that intervention for Bear. During my first miscarriage I requested an IV painkiller and subsequently also got pitocin to move things along. I've had D&Cs for miscarriages too. One of my friends has her cervix sewn shut during pregnancy to prevent premature dilation--this is unquestionably an intervention, but it has prevented two of her children from being born dangerously early. Depending on the circumstances, I could imagine choosing any number of interventions for future situations.

In my mind, what separates 'interference' (bad intervention) from 'help' (a good intervention) or even just from the 'normal process' are two things:
First, the risks. Bad interventions have high potential for negative side effects, often outweighing any potential benefit. For example, pulling on the umbilical cord can help get the placenta out faster (though what is the need?), but it can also cause the cord to detach from the placenta, or cause the placenta to break, resulting in retained placenta, which then involves synthetic oxytocin (like pitocin) and/or the provider going in and literally scraping out the uterus. If the risks are substantial, then I view the intervention as an interference.
Second, evaluate what would happen without the intervention. Is this intervention unquestionably helping (improving the health or safety of mother or child?) or is it based on convenience, preferred timing, or lack of patience? Frequently, labor augmentation or cesarean sections are used because of "failure to progress" in labor, but since normal labors can last hours or even days, many natural birthers have begun to refer to this practice as "failure to wait" and consider those interventions unnecessary. Given some time, the vast majority of those "failure to progress" labors would result a vaginal birth (without drugs, and without surgery). On a related topic, many mothers choose induction of labor because they have reached or passed 40 weeks gestation. However I am not aware of any cases of a woman staying pregnant forever, so sooner or later labor will start! Some pregnancies just last 42 or even 43 weeks. 40 weeks is an average--an estimated delivery time--not an expiration date, (and while I appreciate that it is hard to wait, induction of labor is not warranted just because of a calendar date).

Using those two criteria, let me go back and evaluate the initial situation that started this whole thought process: my midwife's putting her hands on Eagle when he stalled in the birth canal.
Were there risks associated with her manipulating him? Possibly, though I believe they were minimal, as she was gentle and her intention was to 'unstick' him rather than to pull him out. What would have happened if she had done nothing? In this case, he still would have come on out. He likely would have broken his cord and been born into daddy's hands--which is what happened anyway. There is a small chance that he might not have broken his cord, and instead might have been born more slowly and brought the placenta with him. It would have meant he would have been underwater (and half-in/half-out) for longer, but so long as the cord is attached there is no danger in remaining underwater. Aside from the potential discomfort to me or stress to him of being wedged in the birth canal for an extended time, I think that nothing of significance would have been different.
Consider, however, if his stalling had been caused by what we thought it was caused by: shoulder distocia. In cases of shoulder distocia the baby is caught on the mother's pelvis, and will not come on out without assistance. If we had left him alone he would have remained stuck, and both he and I might have become quite distressed. At some point (later if not sooner) it would have been necessary for the midwife to reach in and work him loose.
So was she interfering or helping? Technically, her action was not necessary, or at least was not necessary in the timetable in which she acted (she could have waited and watched a bit before deciding to touch the baby). However, it was not harmful or risky. It did not really affect the overall process or outcome of the birthing. Finally, consider that she did not push Hubby aside when she reached over--he moved aside to invite her into the space. We chose and trusted her as our birth assistant, and in that moment he wanted her assistance. So I feel comfortable in designating her action as help rather than interference.