If you're going to approach them, do it delicately. Perhaps ask them to add a disclaimer, or up the age from newborn- and let them know you're saying it as a mother, as you've clearly got experience in that department.
I had someone berate me on etsy once because I was selling a glass vial pendant (sold as a 'poison pill' vial) with little sugar pills inside and a skull and cross bones sticker on it. They sent me a message telling me how irresponsible I was for selling something so attractive to young children and how if the vial should break, they would eat the pills inside and die and it would be all my fault. I pointed out to them that the listing was not aimed at young children, that the tiny pills were made of sugar, and that the obvious hazard would be broken glass, which is hazardous to people of all ages- for which I have a disclaimer. They were still adamant the jewellery would kill a child, and telling me that I couldn't possibly have a child, else I would understand her plees :-/
I can tell you I was very insulted to receive a message like that- I'm sure you're much more polite than that, but some people can take things very much the wrong way. It's worth a try to tell the seller, as it may well be a risk- and they surely wouldn't want a lawsuit on their hands.
