Some cross posts here but I will answer LuluBai. A lot of this is my personal philosophy about birth and it's very nice to have the opportunity to put it into words, actually - very therapeutic! Thanks in advance for listening and all that.
I have been thinking about this very question quite a bit recently, after No 3 being the hardest. My theory is that birth can get a bit easier with practice, because you push in a more efficient way, and possibly keep calmer generally.
But if I was going to be really honest, I think a big factor in successful births is the size and position of the baby in relation to your pelvis, which changes with every baby.
So many smug mums who boast about not having pain relief and doing it quickly are probably just the beneficiaries of good biological architecture in the first place. This is what the experience of my second birth was like, but I secretly think that a lot of chiropractic in the lead up to the birth helped the natural processes along, and that I am not a supermum, although a good birth like that can feel really empowering and I got a buzz out of having done it 'well'.
On the other hand, if you are in labour for 24-36 hours, really suffering, hospital is probably the place to be because it may be that the baby is just too big or too uncomfortably placed for nature to do its job.
With this baby I know I am starting from behind because my pelvis is a mess at the moment, so I am now having as much chiropractic as possible with someone who treats a lot of pregnant women, to optimise the way my joints behave, and I am going to make sure I have a water pool on hand because I think this helps the mother and baby find a really good position to help the process along, eg floating like a frog, which is hard to do on dry land!!
I get very bothered by the Whipps Cross Hospital programme at the moment because practically every birth I see on there involves mothers lying down on a bed constricting their pelvis and not using gravity to get the baby out. You need every millimetre of pelvis you can get to 'do' birth vaginally, so I don't understand why they even have beds in delivery rooms these days, as they have known about this for decades now.
I have been re-reading the Optimal Foetal Positioning stuff in the light of this and I am feeling very evangelical at the moment about it as a result.
So in summary, yes, I think births can get easier as you get more knowledgable about what works for your body shape, but also it can help if you get yourself in good shape physically to start with as well, at least a few weeks before the birth.
Hope this is not too long a post for everyone!