Jamie Lynn: No Longer Pregnant

JL walked into the Mississippi Southwest Regional Medical Center around 4:30 A.M. this morning ... and squeezed out the 6 lb 10 oz pup just a few hours later. We're told Jamie Lynn was "extremely nervous" before the birth, and started to panic about going into labor. But our spies tell us big sister Brit, who had flown in the day before, "made a big difference" and helped a ton -- giving her advice, support and encouragement.

We also hear JL's bro Brian was on family patrol, calling everyone with the news. As for a name -- the kids didn't narrow it down til the very last second. People says lil' Spears' will be called Maddie Briann.