Kevin Federline -- Hit Me With a Baby One More Time!

Kevin Federline is a lot of things, and one of them is fertile .... baby #6 is in the oven ... TMZ has learned.

Sources connected to the fetus tell TMZ ... Kevin's wife, Victoria Prince, is 6 months pregnant with their second kid. Check out the photos and behold the subtleties -- Victoria is wearing a jersey that says "Juan Moore Federline 6."

Kevin famously has 2 kids with ex-wife Britney Spears, and 2 more with baby mama Shar Jackson.

He truly is Papa ZOW!