Pot belly

This may sound weird, but around that age I remember having to constantly remind myself to tighten up my abs - ie suck in my tummy.  Before that, I had not even worried about my belly pooching out.  But around 10, I became self-conscious, and tightened up my stomach muscles whenever I thought about it.  After some time, I no longer had to consciously tighten, and my stomach was much flatter.  For me, it was just developing and engaging the muscles.   Hope that helps.

try cutting out or really minimizing wheat, dairy and sugar. I always had a bigger tummy as a teen/young adult, even though I was a normal weight. In my 40's I got sick of it, started a more serious fitness routine that included cardio and weights, and cut wayyyyy down on grains and sugars. Presto, over 6-8 months I lost 18 lbs and my tummy is much flatter. I also rarely have gas anymore. Try it w/your daughter! 

How physically active is your child (or are you?).  There are many body types and it's hard to say what the issue is without considering family history and talking to a professional.  A pediatrician might not really know, perhaps someone who knows about fitness or diet could help.  Maybe finding some exercises for your daughter to work on the abdominal muscles could help.  As one of the other commenters said, I too had become aware at a very young age of my ab muscles, not wanting to have a pouching belly) and just naturally tightened them (which helped with my posture) and when I met my husband he made comments about how it was unique that I always tightened my ab muscles.   Also, I have read via online searches that over the last 20-30 people have a lot more abdominal fat because of so much hidden high fructose corn syrup that is in processed foods, which causes this.  I notice this a lot when I am out and about "people watching" and wonder if it is a difference from years ago before there was so much processed, packaged food, fast food, etc.  I gave up all gluten and sugar about 2 years ago (I eat only food I make from scratch, whole unprocessed, fruit, veggies, grains, chicken, and definitely no packaged foods) and I have a lot less fat than I used to, especially around the middle. 

Yeah, "suck in your stomach" is the answer, i.e. change your posture. Some women are just built like this. I can't imagine the amount of weight I would have had to lose in order to have a perfectly flat stomach while slouching -- I was 5'4" and 103 pounds at age 30 and that wasn't thin enough. But I trained myself at about that age to keep my stomach sucked in, and I looked normal (and moved/acted normally) and no one ever mentioned anything about it. Unfortunately my body image was permanently ruined by this genetic luck, and I've worn baggy clothing for my whole life and consider my body ugly and disgusting. I hope your daughter can have a better experience.

I am surprised that in this Berkeley-centric advice section, nobody yet has pointed out that 10 is a very sensitive age for girls and their self-image. Why would the doctors "worry" about a "pot belly" (even this term strikes me as pejorative) in a healthy child? Why would you? I point this out because my young daughter looks like me in many ways... including her copious body hair, which I have hated on myself my entire life (well, now in my 40s, I'm used to it!). Many times already in her short life, I've come close to mentioning it. But it doesn't need to be an issue for her. Just putting this out there for your reflection... how Berkeley can I be. Good luck. Raising a daughter to feel beautiful is a real challenge in today's society.