Making babies has rather suddenly become "in" again, or so the infernally vigilant trend-watchers keep saying, and if so, ABC's new limited-run sitcom, "Baby Makes Five," at 8 tonight on Channel 7, is yet another sign of the times. Have there ever been times as crowded with signs-of-themselves as ours? Oh well--a thought for another day.

Those who look for hills to head to merely at the prospect of a sitcom about a couple with three cute-cute children to whom even cuter twins are born could probably not be converted by a half-hour's exposure to tonight's premiere, but within the confines of the genre, it is a charming, funny, friendly show, executive-produced by comedy veteran Mort Lachman, written by Sy Rosen and directed by Tom Trbovich.

In addition, it pairs one of the most personable husband-wife combinations in recent sitcom memory: Louise Williams, blithe and unaffected and wisecracky as Mommy, and Peter Scolari (the shorter of the "Bosom Buddies" on that deceased series), swift and warm and flip as Daddy. Scolari is sort of a young, and palatable, Dudley Moore, but unlike Moore, he doesn't tug at your sleeve until you think your arm will fall off.

The first half of the premiere parades the three tots before us for some cuddly domestic comedy. The children are not as showbizzy or mechanical as is usual in entertainments of this sort, and they express anxieties, concerns or bad habits that seem indubitably authentic, from Little Annie's "I gotta make poo poo" to Michael's way of turning a whimsical bedtime story into a gruesome thriller that sends his little sisters screaming to Mommy.

But some viewers should perhaps be warned against the second half of the program, when the twins are born. The camera and the comedy follow the mother and father into the delivery room where the baby (babies, as it turns out) is to be born by the Lamaze Method. While hardly rigorously realistic, the sequence includes the sighs and groans and borderline screams of the mother in labor. One can see this depiction as a breakthrough or a vulgarity, depending on the point of view--but purely as a piece of TV sitcom craftsmanship, the sequence is directed and acted with a sure-handed frenzy and professionalism that are in their way exhilarating.

Except for formula insult jokes exchanged by the husband's mother (Janis Paige) and the wife's mother (Priscilla Morrill), "Five" is about six baby steps above the usual TV comedy. Six small steps for baby, one happy half hour for mankind.