It’s the night before their only son’s fourth birthday party, and somewhere in middle America, a middle-class mom and dad, dressed in bathrobes, are wrapping gifts and hanging streamers. Enter their darling boy — played by a 250-pound man in pajamas.

That’s the opening scene of “Birth and After Birth,” the Tina Howe play now having its New York premiere at the Atlantic, some 34 years after Ms. Howe wrote it. A dark, absurdist comedy about women competing over their fertility, “Birth and After Birth” was a tough sell in the early 1970s. In the program notes, Ms. Howe says she stuck the play in a drawer after “producers, [who] had never seen anything like it, ran screaming for the door.”

Thirty-four years later,”Birth and After Birth” (directed by Christian Parker) remains an odd duck. It starts off as a perky American living room sitcom. The running gag is that Sandy (Maggie Kiley) and Bill (Jeff Binder) just can’t stop doting on precious little Nicky (Jordan Gelber) — except when they’re screaming at him.

Sucking on his thumb as he comforts himself after his latest misdemeanor, Mr. Gelber as Nicky is uncannily childlike. His smart performance nails the gestures of a 4-year-old — the gleeful dash, the noncommittal shrug. And of course, there’s the fact that Nicky physically dwarfs his parents, which makes him slightly scary when he throws his toys or overturns his little wagon.

Underneath these standard parent-kid showdowns lurks a creeping anxiety, which erupts in weird bursts of absurdism, like Sandy spontaneously losing a tooth or inexplicably pulling handfuls of sand from her hair. The anxiety seems to radiate from Sandy’s womb; having had Nicky, she now insists that every other woman should experience childbirth — especially her cousin Jeffrey’s wife, Mia, a childless career woman.

Sandy’s obsession with childbirth is the crux of “Birth and After Birth” — and, according to Ms. Howe, it’s also the thing that made the play a non-starter in the theatrical market of the 70s. But ironically, what made the play verboten in the ’70s makes it feel rather quaint now. There is no longer anything fresh in the idea of a childless woman representing a psychological affront to a stay-at-home mom. (And, in fact, the play’s strict division between working women and mothers proclaims it as the product of another era.)

Ostensibly, the mommy theme is the play’s reason for being, but in fact, it’s one of the weakest elements of this production of “Birth and After Birth.” Ms. Kiley’s Sandy is a bland, wheedling woman, a neatnik who knows all about getting stains out of the carpet.She’s no match for the freewheeling, agreeably kooky Mia (the excellent Kate Blumberg), who spends her days trudging through obscure jungles, studying primitive tribes with her fellow anthropologist and husband, Jeffrey (Peter Benson). Mia may be just as loony as Sandy, but hey, at least she’s not a drip.

With the audience’s sympathies all on Mia’s side, there’s no potential for a seesaw debate about the comparative merits and drawbacks of parenthood. And when Ms. Howe’s script piles on the thematic material — with a flashback to a tribal birthing ritual and a confusing, surreal sequence in which Mia appears to die in childbirth — the bits come off as gimmicks.

What really works in “Birth and After Birth” is the straight-up comedy. Ms. Howe shows a great ear for the American absurd and her send-up of the modern American household hits the bull’s-eye, from the asinine rules (“Open your cards first!”) to the Hallmark sentiments (“A birthday blessing for a wonderful guy”). The parents’ slavish attention to Nicky — each of his staged milestones is documented on video — looks especially over-the-top next to Jeffrey’s slides of tribal children. And there are inspired comic sequences, like the one in which Nicky wickedly turns a “Simon Says” game into a fart noise contest; Dad giddily plays along, until Mom sniffs, “If this is the only way you can celebrate Nicky’s birthday, it’s just pathetic!”

“Birth and After Birth,” with its constant shifts in tone and its slow first act (before the arrival of Jeffrey and Mia), is not an easy play to stage. Mr. Parker manages the wild swings from sitcom to Theater of the Absurd about as well as anyone could; his use of a jungle scene behind the translucent back wall does much to smooth the biggest bump in the road — Mia’s strange faux-childbirth and mock-death. He excavates much of the humor in “Birth and After Birth,” though he never finds a way to meld this pile of themes and scenes into a coherent whole.

Until October 29 (336 W. 20th St., between Eighth and Ninth avenues, 212-239-6200).