From Osher Doctorow

Lee Smolin's late 1990s popular book also indicated support for the
"Baby universe" theory generated by either black holes or other
singularities. I have forgotten who originated the "Baby universe"
theory (Scientific American had an article about it some time ago), but
it's a quite plausible theory that doesn't seem to be at all required
by Smolin's Loop Quantum Gravity.

Osher Doctorow