This is actually a routine check that ped's choose to do at either a 6, 9, or 12 mos visit and is a finger prick. I am one who doesn't go to a well visit unless I really want to discuss something or have a concern (we don't vax, so its really unnecessary for us). Our ped is also a lactation consultant and fan of AP, and I enjoy seeing her once in a while, though. HOWEVER, I must say that I am glad at 9 mos. I happened to be there when she recommended these finger pricks. Ds didn't even notice the pricks (I nursed him during it) - and we ended up finding out that he had a pretty severe iron deficiency. It took me and the ped by surprise because he is SOOO active and exclusively breastfed until 8 mos. or so when we introduced some foods like banana, avocado, sweet potato, the norms. She was shocked that his iron levels were so low because even though he was born 1 month early and only 4 lbs 13 oz, he is developing either right on or advanced in every area. After further testing, which meant more blood (3 vials taken from his little arm - which I think upset me more than him, he just stared at it), I did tons of research. We think we have it figured out as to why he was low in iron (because that is not typical of a breastfed baby unless other factors play into it) and now I have learned how to include more iron in his diet and getting things into him to help his body create more red blood cells, etc. But, I always think, wow, what if I never knew? Maybe he'd turn out ok in the long run, but maybe he would have suffered learning problems later...we'll never know.
You don't want to wonder what if, yk? Strange things happen and not every child fits into a box. And as far as the risk factors go for lead, I have heard tons of moms say that they were shocked that their child's lead test came back high.
Just do it. It won't bother him and it will give you peace of mind. Both of those things are important levels to know about I think. This is one of those things that is just not a bad medical intervention. We would've never known of his iron deficiency because he wasn't showing symptoms (yet).