February 5, 1988 | Filmmaker John Hughes, heretofore the poet laureate of American teen-age foibles, has a marvelous coming of age in She's Having a Baby.

Until now, Hughes has been widely known, if not universally loved, for his comedy-dramas of teen angst (The Breakfast Club, Sixteen Candles) or mild-mannered rebellion (Ferris Bueller's Day Off). As relentlessly prolific as Stephen King, he has turned a sympathetic if not downright fawning eye on such pressing concerns as high school peer pressures, picking the right date for the prom, and creative goofing off.

Even when his scripts have been directed by someone else, the films have reflected Hughes' trademark glibness and pop culture fluency. And even when he has dealt with nominal grown-ups, as he did in Planes, Trains and Automobiles, Hughes made his adult characters behave like the detention class of The Breakfast Club.

But She's Having a Baby is something else. Starring Kevin Bacon and Elizabeth McGovern, two of the most attractive and talented actors of their generation, it is a warmly perceptive study of the first six or seven years in a contemporary marriage. It could turn out to be just a happy aberration in Hughes' career. Indeed, he actually wrote and directed it before Trains, Planes and Automobiles, so he already appears to have backslid. Even so, taken on its own terms, She's Having a Baby is an unadulterated delight. Taken as a John Hughes film, it is remarkable.
 
This may well be the most wise, witty and well-observed American movie about marriage and commitment since Two for the Road. No kidding. It's difficult to say what will tickle you more -- the richly amusing script, the beautifully nuanced performances or the gentle shocks of recognition.
 
Despite the title, She's Having a Baby doesn't delve into parental hopes and fears until the final half-hour or so. Most of the movie, a first-person narrative from the husband's point of view, is a very funny, extremely perceptive comedy-drama about how two people can be married for a long time before they really become a couple.

The actual wedding is a scream, with Jake (Bacon) uneasily considering a flight from the church, and Kristy (McGovern) making overwhelming demands in Jake's worst fantasies. Jake's best man, Davis (Alec Baldwin), is not exactly inspiring: ''Well,'' he responds as Jake expresses his pre-nuptial anxiety, ''maybe it will work out. Who knows?'' Meanwhile, Kristy's father (William Windom) is furiously disapproving. ''People don't mature anymore,'' he rasps. ''They stay jackasses all their lives!''

But not really. As She's Having a Baby underscores, people can grow up and accept responsibility -- provided they have someone nagging them into doing it.

Some audiences may object to the movie's idealized depiction of Kristy, a steel-spined support system who makes most of the important decisions. She's the one, for example, who decides to stop taking the pill, to start working on having a child. But even though the character is sketchily written -- we never see her at work -- she is played with such level-headed intelligence by McGovern that the character winds up having surprising depth and texture.
 
Trouble is, for a long time, those qualities are overlooked, or underappreciated, by the self-absorbed Jake. A would-be writer with an unmarketable liberal arts degree, Jake feels he has ''sold out'' by working as an advertising agency copywriter. He complains of ''slave wages,'' though he clearly can afford a BMW and a nice home in a Chicago suburb.

He's jealous of Davis' free-wheeling womanizing. (The scene where Davis shows up with a spectacularly sluttish date is hilarious.) And, worst of all, he fears, as every husband has at one time or another, he got roped into something without being fully aware of it. ''I stumbled into marriage, drifted into a career,'' Jake muses. And then, he backs into fatherhood.

You don't have to be married to appreciate She's Having a Baby, to enjoy the growth of the characters. But if you and your mate have ever tried to have a child, if you've ever worried that one of you can't have a child, you may well hurt yourself while laughing at the scenes where Jake and Kristy find conceiving can be inconceivably difficult. Funniest of all is the moment when Kristy suggests that, ahem, maybe he, not she, should see a doctor. ''Maybe you can't get me pregnant,'' she delicately suggests. Instantly, Jake's defense mechanism for his wounded male ego snaps on: ''And you really believe that?''

She's Having a Baby is filled with this sort of dead-on-target humor. At one point, Jake considers his suburban neighbors, all them somewhat older than he, and imagines them mowing their lawns in a Busby Berkeley production number. If you and your spouse have ever been the youngest couple on your street, you will understand.

With his wholesome good looks undermined by wary eyebrows and a skeptical grin, Kevin Bacon is perfectly cast as Jake. He gives a fearless performance, not holding back from being a selfish lout in his less attractive moments.
 
Bacon is good in his conspiratorial moments with Alec Baldwin, who brings a nice touch of burnished sleaziness to Davis. And he's even better in developing a comfortable give-and-take with McGovern. But Bacon is best of all in those moments when guilt and desire play across his face, and it looks like desire might win.
 
She's Having a Baby takes a dramatic turn at the end, just what you would expect in a John Hughes film. But the audience is willing to go with the flow, because Hughes makes you care about, and identify with, the characters on screen. After seeing She's Having a Baby, some couples will be thoroughly convinced Hughes has been eavesdropping on their lives, on their most anxious and embarrassed moments. But they will be laughing, like the rest of us, at every deep, dark secret Hughes has revealed for the world to share.