What gives? Even formula makers say “breast is best.” Nursing reduces a baby’s risk of diarrhea, ear infections, urinary-tract infections and bacterial infections (and perhaps food allergies, obesity and diabetes). It also lowers a mom’s risk of breast and ovarian cancer—and, since it burns 500 calories a day, helps her lose weight. And it’s free, while formula costs about $1,500 a year. Yet new evidence shows that there has been a decline in the number of women breast-feeding, reversing a steady increase over the past three decades. “The culture does very little to support mothers in what they need—information, maternity leave, places to nurse,” says Bernice Hausman, author of “Mother’s Milk.”

A quarter century ago, one in four new moms tried breast-feeding, and only one in 20 stuck with it for a year. By 2002, almost three in four started breast-feeding in the hospital. But last year, the number had dropped to 64 percent, according to a long-running Mothers Survey by formula maker Abbott. At six months, the percentage of women who were still nursing was only 30 percent; at one year, it was only 19 percent. “Our real problem is duration,” says pediatrician Ruth Lawrence, chair of the AAP’s breast-feeding committee. The longer a woman nurses, the greater the benefits to her and her baby.

Much of the problem seems to be that Americans associate breasts with sex, not milk, and as a result, feel squeamish about public nursing. (While two out of three Americans think breast-feeding is the best way to feed a baby, a quarter say they feel uncomfortable seeing women do it.) In a study for the U.S. government, 48 percent of women said they would feel uncomfortable nursing their own babies in a park, store or mall. “We define breast-feeding as good, and we define breast-feeding as disgusting. We have this split personality about it,” says Jacqueline Wolf, associate professor of the history of medicine at Ohio University. Even MySpace has recently removed photographs of mothers nursing their babies.

Out of concern that not enough women are breast-feeding, a growing number of states are passing protective laws and policies. Today 38 states give women the explicit right to nurse in public, and 23 states exempt it from public-indecency laws. Twelve states have laws addressing women’s right to use a pump to express milk at work. And the governors of New Mexico and Oregon recently signed similar legislation, which gives moms (unpaid) lactation breaks and a clean and private area to pump (not just a bathroom stall). Federal legislation may be on the way. In May, U.S. Rep. Carolyn Maloney re-introduced her Breastfeeding Promotion Act, which would amend the Civil Rights Act of 1964 to protect breast-feeding and to provide a tax incentive to businesses that establish lactation areas.

In a recent survey, the International Formula Council asked moms with kids under 12 months why they would not breast-feed. Most cited medical reasons, followed by going back to work, problems with the baby’s latching on and concerns about the baby’s not getting enough food. The AAP’s Lawrence believes breast-feeding is all about confidence.

Part of the confidence comes from feeling comfortable to nurse. A woman’s right to breast-feed—and a baby’s right to the best nutrients—“shouldn’t be abridged because some people are squeamish about what they’re seeing,” says Chris Musser, who started a blog called The Reluctant Lactivist after a grocery-store manager told her to cover up while she was feeding her then 2-month-old son, Luc. After all, “into the 18th century, women who breast-fed were painted,” says pediatrician Naomi Baumslag, author of “Milk, Money and Madness.” “They were considered beautiful.” Maybe Maggie Gyllenhaal should head back to that park.