Next fall, fashion designers want to impose some structure on women's lives again.

When New York's week of fashion shows opens Friday, America's leading designers will be unveiling suits, dresses and coats with more defined shapes and tailored cuts for fall 2007. Designers such as Diane von Furstenberg, Donna Karan, Nanette Lepore, Tommy Hilfiger and Phillip Lim are all planning to show structured silhouettes reminiscent of the 1950s.

Among the big looks for fall: the egg-like "cocoon," a silhouette fitted at the top and ballooning out before tapering back in at the knee or below it. The style, while difficult for some women to wear, emerged in fashion in the 1910s in French designer Paul Poiret's collections and was popularized by Balenciaga in the 1950s.

Other styles to look for during the week include high-waisted skirts; full, structured sleeves; and pants and coats with wide collars in the style of Jacqueline Kennedy's wardrobe. Some of the tailored looks are a touch sporty -- Michael Kors is offering a piece that resembles a polished parka. Colors promise to be rich and deep, such as navy blue, forest green and magenta.

By showing collections that focus on couture-like shapes and fine tailoring, designers are elevating their offerings at a time when they're under more pressure to design apparel that sets them apart from inexpensive fast-fashion retailers such as H&M and Zara that have become increasingly adept at creating inexpensive versions of high-fashion pieces. Highly structured shapes, for example, may be harder for mass retailers to replicate successfully.

"If people are going to be paying so much for clothes, they want something special, sophisticated," says Valerie Steele, fashion historian at the Fashion Institute of Technology in New York. "This implies a kind of connoisseurship. Women who are literate about the history of fashion are going to go, 'Oh, this piece is Poiret or Balenciaga channeled by this contemporary designer.'"

The move to more defined and shaped clothes is also a classic illustration of the fashion pendulum swinging back. After years of flowing, bohemian fashion, designers moved away from the trend en masse in collections for fall 2006. That season, fashion dabbled with structure by layering coats, jackets and long sweaters over leggings.

The '80s-style bubble skirt was also reintroduced last fall. "For four or five years, fashion really relied on color and print and ornamentation. The bubble skirt was the first time in a while that just a silhouette influenced everyone," says Robert Burke, head of New York luxury-goods consulting firm Robert Burke Associates.

For spring, fashion designers continued adding more structured pieces, with many designers introducing geometric trapeze dresses and mod-style A-line shifts. Now the structured trend has gained steam.

"Fall is a return to classicism," says Donna Karan, who will be showing a fitted skirtsuit that skims the body and is tapered at the waist, marking a sharp contrast to the baggy smocks and flowing, oversize blouses she created for spring.

Even Diane von Furstenberg, famous for her trademark wrap dresses, says she's showing more structured pieces for fall, some in a felt jersey fabric that feels like a stiff doublefaced wool. "It's straighter, much cleaner, and the silhouette is a little boxier than it usually is," Ms. von Furstenberg says.

A retro refinement is reflected, too, in designers' fall color palette of rich colors, such as burgundy. Ms. von Furstenberg says "beet" will be a significant color in her show Sunday afternoon. The moment of inspiration: "A few months ago, I spilled some beet juice and I just thought, 'This is the most beautiful color in the world,'" she says. Designer Tracy Reese says she's planning on showing a series of ensembles done in just deep magenta and black.

Consumers may scratch their heads over why so many designers hit on similar themes at once, but industry observers say it isn't that surprising. Designers often share similar visions in color or patterns, in part because many shop for fabrics at the same place -- the Premiere Vision fabric show in Paris. When it comes to trends such as shape, Mr. Burke, the consultant, says similarities can reflect a natural group reaction to a trend -- in this case a desire to move away from flowing and unstructured looks. Often, too, designers get small previews of others' collections or pieces in trade publications.

Fall's striking shapes are generally good news for retailers, as the new looks may inspire shoppers to buy in order to update their wardrobes. "We really haven't had beautifully tailored garments for quite a while," says Michael Fink, vice president of women's fashion for Saks Fifth Avenue.

But others warn that silhouettes that are too extreme could be a hard sell. Last fall's bubble shape, for example, sold well mainly to younger consumers, at a lower price point, Mr. Burke says.

It remains to be seen whether American women will embrace the cocoon. The shape first appeared just before World War I in the structured, rounded dresses of Mr. Poiret. Balenciaga ushered the shape back in with rounded coats in the 1950s.

This time around, designers are showing more subtle versions than those of the 1950s. A modern "cocoon" by designer Doo-Ri Chung is done sweater-dress style in a soft fabric. Tommy Hilfiger, nodding to Dior's 1950s formal sack-style silhouettes, will show a cocoon in a chunky cable-knit, which gives it some of the couture-like volume and shape but without the stiffness.

For some of us, cocoons can be forgiving. "If you have large hips, it camouflages it a bit," says designer Carmen Marc Valvo, who will show several cocoon-shaped coats and cocktail dresses at his show Feb. 9. "If you're skinny, well, everything looks good on you because you're skinny."

Amy Gamber, a 41-year-old personal shopper and bartender, says she is eager to try out the new cocoon silhouette. "I would like for us to look more like grown-ups again," says Ms. Gamber, who lives in Austin, Texas. "When you're 41, there's only so much babydoll you can do without looking really silly."

When she shows on Monday, designer Nanette Lepore will be joining in the egg-shape trend. She plans to show a tunic in a heavy fabric that's fitted at the bust and flares out into a cocoon shape. Phillip Lim, who designs the high-end 3.1 line, is offering dresses in the shape of elongated cocoons. "There's a strictness in the structure that causes the wearer to walk with a certain pride and elegance," he says. Designer Peter Som is showing a tailored collection, too, but one that is cut to fit much closer to the body.

In keeping with the more formal mood, many of fall's new looks tend to be matching outfits, signaling a move away from the mixed styles of the "personal dressing" trend.

"There's not as much of the intentional mismatching, where you're putting together all these different items to create a look," says Sari Sloane, vice president for fashion merchandising at boutique-chain Intermix. "This is really about the piece -- the jacket, the dress, the blouse."