Marianne C. Stook, mother of 1-year old Annie and 4-year-old Heidi, was determined to give her children the benefits of breast-feeding.

But as a working mother who travels a lot, she often encountered obstacles that demanded raw determination and a dash of levity on her part.

For instance, while on an advertising shoot in New York City with an all-male crowd, Stook asked whether there might be a place she could go to pump breast milk. Indeed there was -- a curtained-off area, hardly the private, sound-muffling nook most women would deem acceptable.

So, what did she do? "I pumped behind the curtain. I knew there weren't any other options so I stuck with my goal despite the awkward interactions before and after."

As vice president of marketing services at a Connecticut firm that helps companies provide work/life services to their employees, Stook was fortunate to have had the benefit of lactation consultants and high quality pumps to help her reach her breast-feeding goals. Without such support, she might have given up.

Studies show that breast-feeding provides the best balance of nutrition for babies and provides all sorts of protective health benefits. It also helps the mother lose weight after her baby is born.

Despite its many advantages, breast-feeding remains a challenge for women in the United States, with rates of initiation and duration trailing optimal levels. In 2001, 70 percent of mothers initiated breast-feeding, 33 percent were still breast-feeding their infants at six months and 18 percent were doing so at one year, according to government data cited by the American Academy of Pediatrics (AAP).

Rates of exclusive breast-feeding -- no water, juice, formula or baby food -- were much lower. At six months, only 17 percent of women were breast-feeding their infants without any kind of supplementation.

Yet that is exactly the goal the nation's pediatricians have set for mothers and their infants. Based on mounting research supporting the value of human milk, the AAP in February issued a revised policy recommending exclusive breast-feeding for approximately the first six months of a baby's life. Mothers should continue breast-feeding for at least the first year. And beyond that, the group endorses breast-feeding for as long as mutually desired by mother and child.

"We're learning more and more about the importance of exclusivity," explained Dr. Jane A. Morton, a member of the AAP Section on Breast-feeding, which issued the policy update. Exclusive breast-feeding in the first six months seems to provide protection against the incidence of allergic symptoms in children, for example, and it can protect against infections, not only as nursing infants but later in life, she noted.

Other studies have indicate that breast-feeding can decrease the incidence and severity of conditions such as diarrhea, ear infections and bacterial meningitis. And some research suggests breast-feeding may even protect against sudden infant death syndrome (SIDS), diabetes and asthma, according to the AAP.

By introducing formula or solid food earlier than six months, "you start diluting some of the benefits down," said Morton, director of breast-feeding medicine at Stanford University Medical Center in Palo Alto, Calif.

For women who must return to work before their infants are 6 months old, the AAP policy may present a significant challenge, experts acknowledge.

"It's a very high bar," Stook agreed. "It requires an extra level of commitment on behalf of these women, and without having a supportive environment you can only put up with so many bumps on the road before you give up."