When we bubble wrap children, in cars or on sleds, we forget what we really need to protect them from. Take the tricycle. In our neighborhood in Connecticut, kids on tricycles almost always wear helmets; in New Mexico, they're the law. Unlike sledding, the rationale isn't that tricycles are dangerous the way bicycles are. It's that early use is supposed to acclimate children to wearing helmets.
This might seem like a smart strategy—a child who's never been without a helmet is less likely to be bothered by it—but it teaches the simplistic, misleading lesson that tricycles and bicycles are equally dangerous. To me, making these distinctions is what's most important: I want Isaiah, who's almost big enough to reach a tricycle's pedals, to learn to tell serious risk from reasonable risk. This is the central problem of parenthood: I can't protect my son against everything. I have to teach him to protect himself. It's a hard enough task without confusing him about what's dangerous and what isn't.
Besides, I think there's a danger in requiring children to wear a helmet sledding. It's clear that if parents are required to buy helmets for children—and have them handy and remember them—fewer children will end up whizzing down a hillside. That's happened with bicycles: In a recent paper (PDF) on helmet laws, a pair of economists found that the new regulations were effective at preventing injuries, but they were also effective at preventing bicycling. In the wake of mandatory bike helmet laws, fewer children rode bikes. Given all the concern that children these days are often inside and inactive, and the looming health risks of childhood obesity, it seems self-evident that there's a risk to not bicycling or sledding.
It's only if you want to prevent injuries above all else that less or no sledding is a good thing. That's why doctors and safety experts aren't necessarily the best people to decide whether a helmet is necessary. At the very least, they shouldn't be the only ones, since their definition of risk—the one I encountered in our blood-soaked child-safety class—is just too narrow.
Dire warnings or no, I'm more worried that Isaiah won't sled than that he'll do it without a helmet. That's why, when he goes sledding for the first time outside of our laps, I'll look out for the trees, and the bumps, and the bigger kids with the snowboards. And then I'll kiss him on the head and push him down the hill. Not quite as hard as he wants.