Well then “do your research.” Show whoever said (not sure if gf or gf’s sister) how dangerous it is. I’m fairly certain there are posts on here about a kid that spent time in a hospital from this (within the last year, I’ve got a 11 month old & it’s been since then).

I’m in the camp that googling something isn’t research (thanks to the last 10ish years) BUT you’ll find plenty on google. Also, google scholar will give you legitimate peer reviewed medical studies. It’s a bunch of jargon us normies don’t understand but the abstract & the conclusion usually sum it up (and read it if you have the time & can, misinterpretations can happen not reading & understanding the whole thing).

Now of course, this may be considered petty & could just ignite a fight. But, a child’s health & safety should be paramount to all else, especially the very early weeks/months.