RIO DE JANEIRO—The other day here, I saw something I rarely encounter back home in Washington. A young woman holding a toddler sat down at the table next to me at a boardwalk cafe. When the little boy got fussy, she tugged down her tank top and fed him in plain view of one of Rio’s largest thoroughfares. No blanket. No shame.

It's not just that Cariocas are far less body-conscious than Americans. Brazil promotes breastfeeding much more aggressively than the U.S. does, and perhaps as a result, breastfeeding is far more common here. More than half of Brazilian mothers exclusively breastfeed their children until they’re six months old, according to the Health Ministry, compared with 16 percent of American moms.

For women who can’t breastfeed, the country offers “milk banks.” Donors pump their milk and store it in glass jars in their freezers, as the AP reported. The jars are picked up by motorcycle messengers and kept in 214 banks around the country, ready for use by mothers who can’t produce enough of their own.

Along with dozens of other countries—but not the U.S.—Brazil bans the advertising or promotion of infant formula. These products are forbidden from having labels that read “ideal for your baby.” In March, the São Paulo municipal government passed an ordinance that would fine businesses or organizations that prevent women from breastfeeding in public.