Most women feel that what they wear is their own business, but what if the woman is also the First Lady?

Rosalynn Carter has made it clear that she can find more important things to talk about, and many would agree with her. But a lot more people are acting like fashion groupies, eager to savor every detail of the First Lady's wardrobe.

"I've waited for six months to get a glimpse of her clothes," said one of many women who called The Post last week, wanting to know more about Mrs. Carter's fashion preferences. "I want to see them all."

The fashion industry wants to know, too. It is already pecking away at Mrs. Carter because she is bringing a sewing machine to the White House, because she wore a vintage dress to the Inaugural parties and because her clothes are not up to the minute, fashionwise.

True, none of the styles in her closets are the ones making headlines in the trade press or on the covers of the fashion slicks. Mrs. Carter's style is conservative: She likes covered up designs with raised necklines and long sleeves. Her clothes aren't particularly youthful but they don't age her either.

They reveal her as she is. They are pretty and neat, comfortable and appropriate and always American made.

What she wears is likely to have little effect on the fashion industry, but that has been true of most First Ladies, with Jacqueline Kennedy Onassis the obvious exception. Betty Ford was a big booster of Seventh Avenue - she visited wholesale showrooms and participated in industry events - but her style was not influential. Indeed, it was criticized by some of the so-called fashion avant-grade.

Mrs. Carter's nonflamboyant style will, of course, determine what others wear to the White House. Extravagant dresses and showy jewels are not in keeping with her ways. Low-key dressing will be more appropriate. And while many of her friends and the wives of her husband's colleagues respond quickly to style changes, unadventurous fashion will be the rule for White House functions.

Despite the Carters' reluctance to hold white-tie gatherings, there will certainly be some, perhaps for leaders like King Hussein, perhaps not for others. White-tie protocol makes like easier because it eliminates the problem of choosing (i.e. second-guesing) what to wear when dining with the President. But it is clearly at odds with the Carter political image, and probably with the Carters' tastes as well.

Less formal dress has created minicrises in the past. When French President Valerie Giscard d'Estaing and President Ford met in Martinique in December 1974, Ford invited Giscard to a barbecue. It caught the elegant French leader and his wife off guard and unprepared for such casualness.

There is little doubt, though, that President and Mrs. Carter will save their jean-wearing for Camp David and Plains, just as Kennedy had his Hyannisport attire and the Johnsons had theirs for the Pedernales.

Mrs. Carter's reluctance to spend a lot of money on clothes does not mean that she doesn't like to look right. In fact, she often comments on the attractive appearance of those around her, according to one of her aides. But Mrs. Carter comes from a poor family, has worked most of her life, and finds it difficult to part with, say, $170 for a dress when there are equally respectable dresses at $70. Lately she has given in to more expensive clothes - she bought several designs from Dominic Rompollo and others.

While Mrs. Carter is hesitant to spend money extravagantly on clothes, the next generation may not feel so strongly. Judy and Caron Carter, her daughters-in-law, are good examples. Both had top designer gowns for the Inaugural parties, and for both, the designers were standing by to make sure the bows were properly tied, the skirts adequately fluffed out.

Mrs. Carter is not likely to annoint any one designer as her particular favorite and will undoubtedly continue to buy off the rack, except in an emergency. Such an "emergency" was the problem of aquiring winter clothes for the Inaugural at a time when there were few cold-weather garments in the stores.

In the past she has bought through Jasons and Cohen's in Americus, Ga. She'll probably use a small Washington area store, like Frankie Welch, Claire Dratch, Dorothy Stead, or Rizik's, to get the same service here.

As for sewing, Mrs. Carter has lots of company - about 50 million Americans - and a very big pattern and fabric industry to appreciate her skills. Amy, not Mrs. Carter, will usually be the beneficiary.

The fashion industry, meanwhile, can probably relax. Carter is the first small businessman to be President since Harry Truman. Rosalynn Carter is a businesswoman who understands the bottom line. It's unlikely that either one will ignore the fourth largest industry in the country.