By Alison M. Rosen
Updated September 12, 2003 11:00 AM

David Letterman will soon have one more reason to stay up late: diaper duty.

The 56-year-old “Late Show” host told his studio audience Thursday that he’s going to be a father, the Associated Press reports. Longtime girlfriend Regina Lasko, 43, is about six months’ pregnant, Letterman said in an episode due to air Friday.

“I have an announcement to make and I’ll be honest with you, I’m a little bit nervous. I have some trepidations about this. I feel a little silly because it’s one of those things where I thought never in my life this would happen,” said the intensely private host.

“And here I am, 56, and by all rights it shouldn’t be happening. But, there’s nothing we can do about it now. And I’m terribly excited about this. I’m scared silly about this. I’m going to be a father.”

The studio audience then cheered for Letterman.

The couple, who are seldom seen in public, began dating each other about 10 years ago when Lasko worked for Letterman on his show, the New York Post reports. They’re not married, but Letterman confirmed that he and Lasko are discussing the possibility.

“I realize we kind of got the cart before the horse here. But, I’m just seeing how much I can get away with,” he said. “But, I can’t do this forever, and it’d be nice to have the kid take over the family business.”

“‘Tonight, David Letterman Jr. and his guests,'” bandleader sidekick Paul Shaffer cracked, according to AP.

“Oh my God, does that sound peculiar,” Letterman replied.

He also joked about becoming a father at his age, adding, “By the time the child has trouble in life, you know, I’ll be dead. I’ll be long gone. By the time the kid’s out stealing cars, you know, Dad will be dead a few years.”

Letterman, who grew up in Indiana and underwent quadruple bypass surgery four years ago, was previously married for seven years to college girlfriend Michelle Cook. “For what I put her through, I should burn in hell for the rest of my life,” he once told Esquire magazine. “I don’t know how to behave (toward women). … I’m no day at the beach, let’s just say that.”