A wet nurse is a woman who breastfeeds a baby who is not her own. The practice became common in Europe starting about 1000 C.E. and in a time of high maternity and infant deaths, these women were in great demand. Wet nurses nourished orphaned infants or fed babies whose mothers were too ill to do so. Many wet nurses also worked in "foundling" hospitals, where abandoned infants were left. Poor women used wet nurses because they had to keep working right after their babies were born. But wealthy women used them as well, because breast-feeding was considered an inappropriate activity for upper-class ladies [sources: Science Museum, Wolf].
Not any lactating female could become a wet nurse. They needed to be healthy, clean, strong and have a pleasant disposition. While wet nursing may sound like a helpful occupation, it actually had many negative consequences. Most babies who were wet-nursed were sent away to the countryside, where wet nurses typically lived. The babies would stay with the them for several years, and suffered a shockingly high mortality rate — as much as 80 percent — likely due to neglect [sources: Wolf].
The practice began to decline in the 19th and 20th centuries, with the advent of pasteurized and canned milk, as well as European government practices granting paid maternity leave to women. While wet nursing is mostly extinct, it still exists in a few pockets of the developing world in 2015, and there has been a small resurgence of the practice among the wealthy in America. This new breed of wet nurse lives with the family and is paid $1,000 a week for her work [source: Gordon].