[My wife is a physician-PhD, so I doubt I am an impartial observer here.--ES]
In reality, medical care during pregnancy seemed to be one long list of rules. Being pregnant was a good deal like being a child again. There was always someone telling me what to do, but the recommendations from books and medical associations were vague and sometimes contradictory. It started right away. "You can only have two cups of coffee a day." I wondered why. What did the numbers say about how risky one, two or three cups were? This wasn't discussed anywhere.The key to good decision making is evaluating the available information—the data—and combining it with your own estimates of pluses and minuses. As an economist, I do this every day. It turns out, however, that this kind of training isn't really done much in medical schools. Medical school tends to focus much more, appropriately, on the mechanics of being a doctor--Emily Oster in WSJ [HT Diana Weinert Thomas via Facebook].
Let's hope that Oster's book actually does what economist do best: examine incentives. What we really need is a critical, data-driven analysis of the institutions and incentives that allow norms be propagated by bio-medical-pharmaceutical-governmental establishments even when founded on not-so-firm evidential basis. As Oster notes these norms make "Being pregnant...a good deal like being a child again;" this suggests that the crucial issue(s) here is not so much flimsy-data. Here's a hypothesis: what makes these paternalistic (sometimes promoted by female physicians) norms 'functional' is living sexism.