By Stephen M. Silverman
Updated November 04, 2003 01:00 PM

David Letterman was missing in action Monday night, as bandleader Paul Shaffer sat in the host’s “Late Show” seat.

But Dave was having some action of his own, it appears: His girlfriend Regina Lasko was apparently in labor with their first child.

As Shaffer told the audience inside Manhattan’s Ed Sullivan Theater: “If you’re feeling that there’s something wrong with this picture — you’re seeing me — (it’s) because Dave is at the hospital waiting for his baby to be delivered!”

Show spokesman Tom Keaney provided no details about the impending birth to the Associated Press, nor did Letterman spokesman Steven Rubenstein.

In September, Letterman told his audience: “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.”

News of a young Letterman just happens to coincide with news that Letterman may be losing his younger audience. The New York Times reports that “Late Show”‘s one and only rival, NBC’s “Tonight Show” with Jay Leno, is enjoying its biggest lead in the ratings in five years.

Leno draws 2 million more viewers than Letterman — 5.8 million to 3.8 million — and Leno is enjoying his biggest edge ever in the competition for the coveted 18-to-49-year-old audience.

As the Times speculates, however, it’s a situation that could still turn around — perhaps with some newfound inspiration from the birth of a child.