Here's my first cut at an answer, from the Canadian Task Force on Preventive Health Care.
I'm struck by a couple things. First, the research on some of the issues is just completely lacking, because other aspects of maternity/newborn care have changed drastically since the last time the studies were done (feeding problems, basically, since time-to-discharge from a normal birth has shortened up so much). Second, I'm a little startled to see the details of well-baby care laid out so clearly, in a way that causes me such consternation.
While well-baby care clearly increases rates of vaccination, the details of which vaccines were given when have changed so much over time that it seems making much of a statement beyond the rates of vaccination (in terms of real health outcomes as opposed to proxies) would be very difficult. I had not realized that asking about sleep, night time waking and crying was considered a measurable component of well-baby care with specific advice associated with a particular parental response: does it bug you? Here's how to implement cry-it-out. Yeesh. (They call it "systematic ignoring". I'm honestly not sure which is worse as a description or mind-set.)
The Canadians note problems with defining eye problems, detecting hearing problems, and whether or not to diagnose hip problems and what to do if you have diagnosed a hip problem. They flat out say that screening for child abuse/advising on child abuse hasn't been shown to help at all. The iron deficiency anemia problem is too complex to get into here. It should be sufficient to note that there's no clear evidence in wee ones that iron deficiency anemia as currently diagnosed and treated is anything other than a poor proxy, at best, for other issues.
The childproofing advice in particular, and the studies that attempt to show benefit, are really interesting.
Given how freaked out everyone gets as a result of height and weight measurements, it's a little shocking that while there is evidence of some benefit, it's not very strong.
Expect to hear more whining from me on this topic. This is at least as shocking as discovering how useless prenatal/antenatal care is.
HEY! YOU! Before you get all over me, I do, in fact, go to prenatal visits and I take them very seriously. I did, for T., more than the schedule of well-baby advised by the Canadians. And I took those really seriously, too.