When Sheila Weidenfeld, former White House press secretary, went back to the White House last summer for her father's swearing-in ceremony as ambassador to Italy she wore a red dress that "looked a bit tired" and sandals she sometimes wore to the pool.

"I wasn't worried about the fact I wasn't the last word in style," says Weidenfeld, who was pregnant with her second child at the time. "There was simply nothing else I could do."

Weidenfeld is one of an increasing number of women having children in their 30s and early 40s, an age when most American women traditionally had stopped bearing children.

Like that of Weidenfeld, who describes herself as "being the age of amniocentesis," the attitude of this group toward maternity clothes reflects more an interest in looking attractive and appropriate than expectant.

"I just wanted to look the way I always had. Not little-girlish and different from my usual look," says Judy Woodruff, NBC White House correspondent. The first maternity dress she bought had a white collar and ditsy little bow and she never could bring herself to wear it.

According to the National Center for Health Statistics, the largest increase in births is among women age 30 to 34. More than half of the women in this age group are working and thus have more money to spend on clothes than younger counterparts.

The tunic top with the word "baby" and an arrow pointing to the mid-section will not do. Neither will the baby-doll look with flared short tops and narrow pants or skirts.

"The point is not that I don't want to look pregnant," says a Washington writer, 40, now in her sixth month. "I just don't want to look like a massive hulk."

Woodruff, 35, made do -- TV camera pulled in for tight close-ups -- with her regular clothes for most of her pregnancy. The first time she wore a maternity jumper (for a broadcast from the White House lawn) was the only time she got a call from the producer asking if she could change her outfit. She did, by wearing the blouse over the jumper.

"It looked awful in person," says Woodruff, "but worked for the camera."

While most maternity shops and departments have responded to the demand with better-quality and less contrived garments, many women supplement purchases with full dresses, caftans or tunics from regular stores. Among the most popular sources: Laura Ashley, whose signature style is a fully-cut smock dress, or boutiques specializing in ethnic clothes, such as Georgetown Cotton, Toast and Strawberries and Batik Walla.

"It took me three pregnancies to learn that some of the best maternity clothes are not in maternity departments," admits Kathleen Jones, 36, a special-education teacher.

"You must be very careful buying non-maternity items because often they will not compensate for the pregnant shape and the hem will rise in front," warns Patricia Brummer, 30, a puppeteer and puppet designer in England before moving here.

Those who can afford the luxury have found the tunics of Yves Saint Laurent, the easy tops of Perry Ellis, the elasticized skirts and oversize blouses of Calvin Klein a handsome transition from normal to maternity clothes. some have made their own versions of these designs; others have simply added fullness to regular patterns.

Only a few secondhand stores, notably Modern Mothers' Exchange and Once Is Not Enough, feature secondhand maternity clothes. Women who have not enjoyed secondhand shopping before their pregnancy, however, are apt to be more reluctant to do so for maternity clothes.

"It takes so much effort looking for clothes when you are pregnant," says Susan Watters, 33, director of the Washington bureau of Fairchild News Service. "I enjoyed the luxury of separate dressing rooms and stores where you didn't have to climb to the second floor."

But borrowing clothes from a friend can be appealing.

"In the beginning you just feel pregnant, not pretty," says cookbook author Joan Nathan, whose husband Allan Gerson is a special assistant to U.N. Ambassador Jeane Kirkpatrick. "And somehow, when someone has made the choice of the maternity clothes before you, borrowing them makes the whole clothes process much easier.

"I feel a very close bond with the women whose clothes I've been sharing," says Nathan, 39. "I don't do that kind of thing normally, but somehow it is more than acceptable with maternity clothes. There is a certain intimacy about pregnancy that only when you have gone through it can you share with someone else. Maybe because a woman goes through it alone."

The biggest boost to Judy Woodruff's maternity wardrobe was not some new-found garments, but the fact that President and Mrs. Reagan -- the focus of her work -- moved to California for the month of August. "You could get away with wearing more casual clothes there, including pants and things that I just couldn't wear on the job in Washington."

Suzanne Garment, 35, associate editor of The Wall Street Journal editorial page, jokes about never finding a magic formula for maternity clothes. "Being 4-feet-10 puts me beyond the tricks of the trade. When you look like a football, a vertical scarf or any other trick just isn't going to help."

Among tricks -- for pregnancy at any age -- from other women:

* Wearing a large shawl over the shoulders and tied loosely in front, to call attention to the shoulders.

* Clipping on a big pin (often stashed away in a jewelry box), also to redirect attention.

* Solving the coat problem with a cape, also a good "extra" for after pregnancy.

* Choosing regular pantyhose -- rather than maternity -- in the largest sizes, or wearing knee-highs and boots, or as one woman suggested, "Just try to be pregnant in warm weather to avoid the whole pantyhose problem."

* Wearing hair longer to better balance a larger silhouette.

More than one prospective father has noticed some strange things happening in their own wardrobes: missing shirts, sweatpants, parkas. But for impeccably-suited lawyer Ed Weidenfeld, the change was even more drastic.

He went to work one day with one brown shoe and one black.

"I guess he didn't want to disturb me," says wife Sheila, "by turning on the light."