If you see “anecdata” next to something I've written, it's my way of letting you know that this is just something I've observed. I may not have looked it up yet, or maybe there's no research that I can find. I like to be transparent in my sources.
I mean, I've been doing this a long time and I've been to a bunch of births, but every birth I attend shows me that I don't know everything. It's humbling that way.