Yes, I think I do/did.
I've never dieted & only vaguely monitor my weight. I'm currently bfing DS (#2).
I think with both my pg I put on about 18kg. I started out slightly lighter with DS than DD though.
I bf DD for 9mths. I was back in my Dorothy Perkins size 10 jeans at 10wks post-birth & definitely didn't do anything regarding diet to lose weight. In fact, pg & bfing make me want high-carb/crap food. DD fed a lot but wasn't a big baby & gained quite slowly (9th centile & put on 'minimum' wkly gain according to HV), so it wasn't as if I was making a chunky baby. I did walk a fair bit too - I liked walking with the pram in the warm weather.
I did hang on to a touch extra weight - I was at the top end of my 'usual' weight until I stopped feeding DD & then lost the last 2-3kg. However, I did have appendicitus at that time too, hence stopping a bit earlier than I liked, so it might have 'helped' the weight loss.
DS is not quite 7mo & I'm back to my heavier 'normal' weight. I'm not quite in all my usual clothes, although my jeans fit again at about 20+wks post-birth, as my waist & boobs are still bigger. I am still eating like a pig though, so hope that when he feeds less/stops altogether, the last 2-3kg will fall off. DS is a boob-monster (& now loving food!!) and put on a 1lb in just over his first wk, so a lot of my extra calories are definitely going into him! I'm walking less because its trickier with a 3yo.
I also tend to eat more in winter/the cold, and as DD was a spring baby, compared to winter DS, & its been the longest winter EVER this yr, that might have contributed. Hopefully will the usual summer diet of salads etc I can drop those last few pounds...
I think I'm lucky though. I'm pretty much always able to eat what I want/balance the naughty with the nice, so despite definitely favouring junk when pg/bfing, I don't gain or lose to much.