A wet nurse is a woman who breastfeeds and cares for another's child. Wet-nursed children may be known as "milk-siblings", and in some societies, the families are linked by a special relationship of milk kinship.
Wet-nursing existed in societies around the world until the invention of reliable formula milk in the 20th century. The practice has made a small comeback in the 21st century.
A wet nurse can help when a mother is unable or unwilling to breastfeed her baby. Before the development of infant formula in the 20th century, wet-nursing could save a baby's life. There are many reasons why a mother is unable to produce sufficient breast milk, or in some cases to lactate at all. For example, she may have a chronic or acute illness, and either the illness itself, or the treatment for it, reduces or stops her milk.
This absence of lactation may be temporary or permanent. There was a greater need for wet nurses when the rates of infant abandonment and maternal death , during and shortly after childbirth , were high. Some women chose not to breastfeed for social reasons. For upper-class women, breastfeeding was considered unfashionable, in the sense that it not only prevented them from being able to wear the fashionable clothing of their time, but it was also thought to ruin their figures.
A woman can only act as a wet nurse if she is lactating producing milk. It was once believed that a wet nurse must have recently undergone childbirth in order to lactate. This is not necessarily the case, as regular breast stimulation can elicit lactation via a neural reflex of prolactin production and secretion.
