Not babbling?

Ca

Anyone else's baby not babbling yet? My little girl will be 10 months in two weeks and our pediatrician said at her 9-month appt. that if she's not babbling by then we should check back in with the doctor. She's very vocal, makes a variety of sounds, mostly vowels, but doesn't string together the "ba ba ba" or "ma ma ma" that's expected around this age. I'm not super worried, just curious.