Christina Applegate is a working mom, and she plays one on TV too

As Christina Applegate embarks on her return to prime-time TV, the central question for her on the set isn’t whether “Up All Night” will get good ratings. Her main concern is: “Do we have an ETA on the baby?”

The 39-year-old first-time mom has just wrapped a scene of her new NBC comedy, which premiered last week, and a production assistant is speaking into a headset, trying to determine when Applegate’s infant, Sadie, will be shuttled onto the production lot. Her mommy really, really wants to see her. So much so that an interview has to be rescheduled because it interferes with bonding time.

A week later, the conversation commences with Applegate cooing about her tot: Sadie recently started clapping, Applegate boasts, impersonating two palms connecting.

“I’m totally that mom, aren’t I?” she said, catching herself.

The infatuation is one the working mom shares with her new TV persona. In “Up All Night,” Applegate stars as Reagan, a talk show producer who (along with her husband, played by Will Arnett) becomes a parent in her late 30s and who is struggling to hold on to the kid-free lifestyle she knew for so long.

“It’s the closest I’ve ever been to myself in a character — the sense of humor, the baby love. It’s there,” she said.

Dozens of baby bottles distance this character from Kelly Bundy, the sexy teenage ditz Applegate played on “Married With Children” for a decade starting in the late ‘80s. The shift is just as drastic in her own life, with the lingerie she once wore as a founding member of the Pussycat Dolls now replaced by a girdle: “I still haven’t lost my baby weight…. There was a human being inside me.”

Despite the parallels in “Up All Night” to Applegate’s real life, the comedy is actually a semi-autobiographical take on creator Emily Spivey’s experience as a later-in-life mom working “rock ‘n’ roll hours” as a writer for “Saturday Night Live.” It translates into scenes like the one in which Reagan turns down the opportunity to attend a picnic at Stevie Nicks’ Santa Barbara home in favor of spending time with her tiny tot. In another, she longs to put on her “slutty outfit” like in the “old days,” when she might have been found dancing on pool tables and doing shots.

“The reality is, it’s really hard,” said Spivey, who also serves as an executive producer along with SNL overlord Lorne Michaels. “I was really set in my ways by the time I had a kid. There was a lot that I wasn’t willing to give up. And I thought the idea of extended adolescence and the way a baby can sort of bamboozle all of that would be funny to explore on a show.”

The comedy isn’t without heartache for Applegate. A typical day on the set begins at 6:30 a.m., with a workday that lasts 14 to 16 hours.

“I get text messages from [Sadie’s] dad or the nanny saying, ‘She just started doing this and this’ — that’s when my heart starts to break,” Applegate said. “I even jokingly said to her nanny, ‘If she tries to walk, push her back down.’”

If the star who overcame breast cancer two years ago seems uncertain about her decision to appear in the series — a decision she made six weeks after giving birth — it’s mainly an adjustment issue, she insists.

“To be honest, I didn’t want to go back to work. At all,” she said. “I was given the script and I just loved Emily’s voice. She came over to my house and I thought, ‘Hmm, I could get along with this lady.’ I was really unsure for a minute though.”

Parenting is an area of pop cultural interest this fall: Sarah Jessica Parker stars in a big-screen adaptation of “I Don’t Know How She Does It,” about a woman juggling career and parenting. “I Hate My Teenage Daughter,” about the hazards of raising teenagers, is premiering on Fox, and ABC’s new series “Suburgatory” looks at single fatherhood. The question is whether any of these will catch on, since a number of past TV shows on the topic, such as “Notes From the Underbelly” and “In the Motherhood,” failed to find an audience.

Working to “Up All Night’s” advantage is the quirky writing of Spivey and the comedic pedigree of costar Maya Rudolph, an “SNL” alum still riding high off her role in the hit summer film “Bridesmaids,” and Arnett, who’s managed to retain his “Arrested Development” prestige through stints on “Parks and Recreation” and “30 Rock” (though, his attempt at headlining Fox’s “Running Wilde” last season proved disastrous).

The series has also gone through a number of revisions. Applegate’s and Rudolph’s characters were set to be sisters when Spivey first wrote the script. That morphed into friends who worked at a publicity firm. Now, Reagan’s workplace setting is a talk show, with Rudolph as the show host. They’re changes producers hope will attract viewers during a time slot that’s likely to be dominated by reality powerhouses.

“We’re not going to beat ‘The X Factor.’ And we’re not going to beat ‘Survivor.’ Let’s just put us against two of the biggest shows on television and then expect us to do well!” Applegate said. “I don’t know if that’s really going to happen. And I think NBC knows that. I think we all kind of know that it’s not going to get big numbers. This is the world we live in. It may live or die there, who knows?”

She paused, adding, “I am that mother! I put everything into perspective now.”

yvonne.villareal@latimes.com