The batteries are dangerous because of their chemistry. Deadly dangerous. There is no danger in swallowing Lego heads. Which was the point. Be aware of what’s actually going to harm your kid.
We had a teen swallow a coin cell and it was allowed to pass. The biggest factors for retrieval seem to be size, a small child may have the object stick, and then if the battery ruptures. The ER doctors seemed satisfied it hadn't done so, and sent us on our way.
“ We get people to swallow pill cameras all the time in our gastro department, and they're bigger than that. The numbers that we'd learned, although I'd learned as part of my pediatric training around what you will and won't pass and where the danger zones are, is that if something's greater than 110 millimeters, then it won't get around your duodenum. And if it's pointy and spiky, then there's a risk of it stabbing into stuff. The Lego heads were neither of those. We've kind of talked about that right at the point of designing the study because we talked about swallowing the classic two-by-four Lego brick, and then decided that that was going to be too pointy. Really, a Lego head is just like a piece of corn, isn't it?”
So no, there’s no danger. Sure, the passing time was the premise but this was done for a) laughs and b) to spread awareness about swallowing batteries.
