I guess it depends. If they're REALLY wet before a feeding, I would change them before since my kids tend to fall asleep during feedings. However if they were only slightly wet I would probably wait until after the feeding and nap. And if they were poopy I would change them right away I hope this somewhat answers your question.
With a newborn I always change before the feeding. Since they are already awake I think it's best to change before, then you can nurse and then just put them back down if they fall asleep while nursing. It's especially important at night.
I have always changed my babies as needed. If they are wet/poopy they get changed. Now I usually wait at least 10 mins after noticing a younger baby having a BM to see if they need to get anymore out. It is usually more common for a baby to be wet/dirty after they have eaten though and like PP mentioned usually babies fall asleep while being fed.
Considering that I use cloth, it is even more important to change as needed (of course, if they're in the middle of a bowel movement [BM] or I am expecting one soon, I'll wait).
Like others have said, I prefer to change before feeding, if possible, because if they don't happen to dirty the diaper while feeding, it's that much easier to put baby back down to sleep. On the other hand, I do probably go through more diapers, because my babies tend to like to have a BM the last few minutes of a feeding.
Also... my girls tended to have VERY sensitive skin with rashes, yeast infections, etc, whether disposable or cloth diapers, so that made it worth it to err on the side of changing diapers more often.
So, I'd say it's a matter of feeling out what works for you, how dirty/wet a diaper might be after a feeding, and how easy they are to get back down for a nap...
I was told after I had DD1 to change her before and after feedings. However, I always just changed her after a feeding to save on diapers (most of the time she was barely wet, and since I was only 18 with not much money I wanted to save) unless she had a BM. With those I would always change right away.
But with both my girls I always waited until after their feeding because 99% of the time they will go to the bathroom again during or right after the feeding.
I did it as needed. I don't remember if I had a schedule. We used cloth too, so we never had her sit around wet or soiled.
I usually change before since both of my boys always fell asleep while nursing. We are cloth users as well though so I often did a finger check to make sure they were dry before I put them down JIC since sitting in wet cloth caused issues. As tiny newborns they tended to not pee until they roused. Both my kids nursed seriously every hour as newbies though.
~Joy~ DS1-8/5/05, DS2-10/18/10 (VBAC#1), DS3- 4/11/12 (VBAC#2!)
We always changed as needed - if they are wet or pooped they get changed no matter if it's before or after a meal or whatever. Newborns poop a lot! I remember going through an average of 14 diapers a day with my girls when they were newborns. I am prepared now though, I have 4 packs of diapers in the babies armoire already LOL
with DS I remember I often changed between boobs - especially at night - he would often fall asleep on the first boob and changing him would rouse him just enough to take the second one - then I knew he'd had a good feed - I don't know if that helped him sleep longer or not, but it worked for us. During the day I'd change him on an as needed basis...