OP, I have the opposite where baby at 8 mo is dropping slightly on growth (from 95 to 75) and weight (from 75 to 50%). But he is extremely mobile and has been for several months (crawling for 3 mo and standing and taking steps for weeks). I have heard that most babies thin out as they move around more--maybe yours is slower to thin out because he is less mobile?
In other words maybe your baby might be heavier in weight because he is crawling later than other kids. Sounds like he is shooting up like a beanpole in height though!

heaigh could also be off as even half and inch can make a huge difference at this point. I would see what happens at the next visit.

OP here---thanks! I hadn't thought about the poop/meal factor---it is the case that this was an afternoon appointment and we have always gone in the morning in the past (plus baby is eating solids now and wasn't last time around) so maybe that accounts for some of it. Also hadn't occurred to me that the rapid head growth might be a concern---his pediatrician seemed fine with it so hopefully all is well. On the up side, everything seems to be growing at the same pace, so that's hopefully a good sign!

Don't forget, a big poop or meal can tip the measurements vastly in one direction or the other.

But yes, my son actually did both- height shot up and weight fell down- and he is still mostly on that growth curve. Also, height measurements can be off depending on how straight/still your child is when measured.

My dd was always in the 50%tile for weight and height. Somewhere around 2 she burst into the 75%tile for height. Unrelated to walking because she walked really early. DH is average height. I am tall for a woman. Not sure it really matter as long as weight percentile isn't way more than height. I think at the 2 year old check up the pediatrician can do an estimate of adult height.

My ds had rapid head growth at about 6 months. This is the type of growth that isn't good. (He turned out fine with just a large head at 5 yo.)

Kids just grow at different rates and times.

...did he/she stay on the new curve, or eventually fall back? Our 9-month-old has been consistently 50th percentile for height and 10th for weight and head circumference since birth, but at his 9-month appointment, he suddenly jumped to 50th for weight and head and 70th for height---wow! (They weighed him twice to double check that it was correct!)

We're perfectly happy wherever he lands, but I'm curious--if this happened with your child, was it a fluke and did he/she bounce back down closer to the original percentiles at subsequent check-ups, or was it the beginning of following a different curve? We're pretty short/petite so I'm just wondering what lies ahead for our little one. If it matters, our baby is not yet mobile but is on the cusp of crawling, so I'm guessing that at least the weight gain may slow a bit once he starts moving, but not sure this is true for the height. Thanks!