FASHION : Support for Moms : Specialty bras for pregnant and nursing women have proliferated. But getting the right fit is still tricky.

Agood friend who recently delivered a nine-pound baby had shaken her head in disbelief early in her pregnancy. “It wouldn’t surprise me if the same company that made maternity underwear also made trash bags,” she said, holding up a nursing bra. A few months later, it fit perfectly.

So it goes when you’re trying to decide what to buy in the way of “foundations”--nursing bras and other specialty garments--to get you through pregnancy and beyond.

“Hormonal changes cause most women to begin changing bra sizes within the first few months (of pregnancy),” said Patty Villarreal, a registered nurse and director of the South Texas Lactation Center in San Antonio.

“Not only will the cup size increase, but a pregnant woman’s chest wall expands, changing both (letter and number) measurements,” she added.

The options for pregnant and nursing women have proliferated in recent years, said Liz Wallace of A Pea in a Pod, a national chain of maternity stores. Prenatal and nursing bras now come in a wide variety of styles, including front closure and underwire, as well as versions for jogging and sleeping.

But “a bra need not be labeled ‘prenatal’ ” to be practical, said Carol Anne Friedman, a lactation consultant and owner of Mothers With Style, a Glendale maternity shop. “Any good-fitting, supportive and comfortable bra will work as a prenatal bra.”

But Friedman endorses nothing but 100% cotton. “Frilly nylon bras aren’t functional,” she said. “When you’re nursing a baby, you want comfort and functionality.”

Villarreal agrees. She also suggests that moms-to-be put off shopping for a nursing bra until the last trimester so the bra can be worn before and after the baby arrives. “Women should opt for a fabric that allows the skin to breathe and a fit that leaves room for growth--and nursing pads,” she said.

Wallace measures clients around the bust line and the chest, then uses a conversion chart to determine cup size.

“If the bra fits you perfectly, it’s the wrong bra,” she explained. “It should be loose through the nipple going up to the bust line. This will accommodate for milk and pads.”

Villarreal cautions against choosing underwire styles for postpartum wear because they may impede circulation.

She added that you should be able to unhook the breast flap with one hand. “‘Practice unhooking the cup while in the dressing room,” she said.

The experts also emphasize the importance of wearing a bra day and night.

“Many women find they cannot go without one,” Wallace said, adding that sleeping bras in lightweight, breathable cotton offer comfort and support.

Nursing moms who go without will probably regret it, Villarreal said. “The long-term effect is the stretching of muscles that support breast tissue.”