Lynch -- who relinquished her title when she went on maternity leave -- gave birth to a baby girl in December with hubby Seth Rollins. She recently returned to the ring ... and is already SmackDown champ.
TMZ Sports talked to Becky and we asked her if she had any advice for Rousey, who also gave birth to a baby girl with husband Travis Browne in late September ... and she did, sorta.
"Don't [come back], cause I'm still on top, Ronda, you won't like it.