MAYBE IT'S the "Juno" effect, but issues surrounding pregnancy and adoption seem to be on TV writers' radars these days.

On ABC Family's "The Secret Life of the American Teenager," there's a pregnant 15-year-old considering her options, while on the CW's "One Tree Hill," one character's adopted and another's tried to adopt. And last night on HBO's "Big Love," another pregnant teen was interviewing prospective adoptive parents.

It's the teen-focused CW, though, that's seemed most intent on milking every bit of drama from adoption by featuring storylines on both "Gossip Girl" and "90210" in which schoolmates discover that they share a sibling they've never met, thanks to long-ago relationships between two of their parents and the decision by the young mothers to have their babies adopted.

On "Gossip Girl," it's a revelation that threw yet another roadblock in the romance between Brooklyn boy Dan Humphreys (Penn Badgley) and It Girl Serena van der Woodsen (Blake Lively), even though their parents have been told the half-brother in question is dead.

On "90210," it's Mean Girl Naomi (AnnaLynne McCord) and New Girl Annie (Shenae Grimes) whose already rocky relationship took a hit when a guy claiming to be their long-lost half-brother turns out to be an imposter.

(Yes, much more has happened since at West Beverly High, but not long after this, I remembered I had a life and stopped watching for a bit.)

Given that both shows had the birth fathers not even knowing there'd been a child, much less an adoption, you might be forgiven for thinking the C in CW stood for Coincidence.

Especially since CW entertainment president Dawn Ostroff insists that's all it is.

"The treatments of the two storylines were totally different," she told me last month at a CW cocktail party in Los Angeles.

Which brings us to "Light Years," a CW pilot Ostroff describes as " 'Gilmore Girls' meets 'Juno.' "

"A 16-year-old has a baby, the boy doesn't even know she has the baby . . . the girl [who was given up] comes back because she wants to get emancipated, because she never was adopted," but has spent her life in foster homes, Ostroff said.

The child, who turns 16 in the pilot, forms a relationship with her not-much-older mother - who's apparently had a far-cushier life - and with her father, though the two aren't together anymore.

Sure, that's potentially a third show where the father of a teenager didn't even know he was a father, "but it's not really relevant," Ostroff said. "It's not what the show is about."

Maybe not. But with the CW perhaps already overinvested in the doings of overprivileged adolescents, it couldn't hurt to diversify their plot portfolio a bit.

3+1 may not add up

HBO's renewed its polygamy drama, "Big Love," for a fourth season, and it's gotten me thinking about the number four.

Four judges so far hasn't proven any better than three on Fox's "American Idol," where Simon Cowell's ability to break ties makes him seem more of a bully than ever.

I'm hoping for better things as we get to the live shows, but I suspect four's not going to be the magic number there, either.

Four's also a problem "Big Love" will be wrestling with in the next few weeks, as Bill Henrickson's (Bill Paxton) courtship of a potential new wife, Ana (Branka Katic) threatens to upset the Brady-girls dynamic of the first three.

(If you don't know what I mean, just close your eyes and imagine Chloe Sevigny's character, middle wife Nicki, complaining, "Marcia, Marcia, Marcia!")

I'm as in love as ever with "Big Love" this season, and one reason is the casting.

Many men wouldn't want more than one mother-in-law, but Bill, who's down to two at this point, gets to butt heads with Mary Kay Place as Adaleen, Nicki's mother and the big picture-minded wife of "prophet" Roman Grant (Harry Dean Stanton), as well as with Oscar winner Ellen Burstyn, who plays Nancy, the still-horrified mother of Bill's first wife, Barb (Jeanne Tripplehorn).

Add in Grace Zabriskie ("Twin Peaks," "The Big Easy") as Bill's own mother and you've got serious mojo on the matriarch front.

Fans of Fox's "House" may also have spotted Anne Dudek - Wilson's sometimes scary late girlfriend, Amber - as Laura, the scariest of the wives of Roman's son, Albert (Matt Ross).

Dudek, who also pops in to the Draper kitchen from time to time on AMC's "Mad Men," where she plays suburban housewife Francine Hanson, doesn't get a huge amount of screen time on "Love." But like every one of the show's many, many wives, she makes the most of every minute she has. *

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