CBS News weekend anchor Russ Mitchell – at the center of a sex scandal in the midst of his engagement – is about to be a new dad. He's already a father from a previous relationship, but we're told exclusively that his new fiance Karina Mahtani (an associate producer for CBS's Showbuzz) is expecting. A new baby on the way in the middle of such controversy over his secret engagement and trysts with other women? There's no way it could get worse.

Unless, you know, there was yet another woman. As Page Six was first to report today, Lady No. 4 is a St. Louis native (like Mitchell) who owns her own advertising business there. The duo were spotted dining at a sushi restaurant on August 13 and sharing a parking lot kiss. Now we've exclusively learned this fourth woman is Sandy Stolberg (pictured). Surely it's only a matter of time before Ladies No. 5 and 6 rear their heads.

Related: All Russ Mitchell coverage

The plot thickens for CBS News weekend anchor Russ Mitchell. Last week we told you about his secret engagement to fellow CBS staffer Karina Mitchell (a Showbuzz associate producer), all while he's been allegedly stepping out on his future bride with a childhood ladyfriend. We're now told that while Mitchell and his mistress had been seeing each other for more than a year, as of two weeks ago they ended things — which means Russ might have been faithful for about as long as Pete Wentz and Ashlee Simpson have been smooching.

Mitchell and Karina celebrated their engagement on Thursday night with a small party at Tse Yang, with Karina's two children from her previous marriage in attendance — though Russ' daughter was nowhere to be seen (and neither were any guests at all from Russ' side). Quite a way to kick off a rock solid future such a short time after Mitchell's "other woman" found out about Karina and hurredly called things off — and ran to Karina and told her everything. But as we reported last week, Karina is still intent on getting married.

An insider who lives in the same building as Russ tells us the CBS anchorman and the other woman were together often. She had a key to his place, in fact.

And to top things all off, new information fingers yet another woman – not Karina – that Russ was allegedly involved with. She, a former WCBS employee, and Russ are said to have dated about two years ago and have continued their romance admist Karina and the second woman.

And you thought Katie Couric was going to strip all the sex from CBS.

Earlier: The Secret Behind CBS Anchor Russ Mitchell's Secret Engagement

On Thursday, Page Six ran an otherwise innocuous item about CBS Evening News weekend anchor Russ Mitchell getting engaged to girlfriend Karina Mahtani, an associate producer for the tiffany network's Showbuzz segments. The hook: They weren't telling anyone — and news of their road to nuptials came only when "a co-worker spotted the bride-to-be working on invitations for an engagement party."

We can imagine why the news-some duo kept their off-air romance a secret to the general public, but not even telling colleagues about their engagement? And not returning Page Six's phone calls to confirm? (The audacity!) Sounds off even to us, and we live in a world where exporting Us Weekly makes sense.

But this afternoon, things became clear when an insider shared the backstory. The reason Mitchell and Mahtani are so coy about their vows allegedly has something to do with your weekend anchor's third-party tyrsts. We're told that for more than a year, Mitchell has been seeing another women – even taking her out to public spots like Gabriel's and Brasserie Ruhlmann in Midtown and Cain Southampton – who he knows from his childhood in St. Louis (though she lives in Manhattan now, too).

We also understand that Mahtani isn't wearing an engagement ring. Meanwhile, CBS is supposedly fully aware of the threeway situation — as is Mahtani, and she is still ready and willing to marry Mitchell.