A wet nurse is a woman who breastfeeds and cares for another's child. Wet nurses are employed if the mother dies, if she is unable to nurse the child herself sufficiently, or if she chooses not to do so. 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.

Reasons 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.O'Reilly, Andrea, "Wet Nursing," Encyclopedia of Motherhood (2010): 1271 There was a concurrent availability of lactating women whose own babies had died.

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.Emily E. Stevens, Thelma E. Patrick and Rita Pickler, "A History of Infant Feeding," Journal of Perinatal Education (Spring 2009): 32–39. (accessed 10 February 2016). Hiring a wet nurse was less expensive than having to hire someone else to help run the family business and/or take care of the family household duties in their place. Some women chose to hire wet nurses purely to escape from the confining and time-consuming chore of breastfeeding.O'Reilly, Andrea, "Wet Nursing," Encyclopedia of Motherhood (2010): 1271.

Eliciting milk

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.E. Goljan, Pathology, 2nd ed. Mosby Elsevier, Rapid Review Series. Some women have been able to establish lactation using a breast pump, in order to feed an infant.Wilson-Clay, Barbara (1996). "Induced Lactation" . The American Surrogacy Center.

Gabrielle Palmer,Lecturer in Human Nutrition at the London School of Hygiene & Tropical Medicine and author of The Politics of Breastfeeding author of The Politics of Breastfeeding, states:

Historical and cultural practices

Wet nursing is an ancient practice, common to many societies. It has been linked to social class, where monarchies, the aristocracy, nobility, or upper classes had their children wet-nursed for the benefit of the child's health, and sometimes in the hope of becoming pregnant again quickly. Exclusive breastfeeding inhibits ovulation in some women (lactational amenorrhea). Poor women, especially those who suffered the stigma of giving birth to an illegitimate child, sometimes had to give their baby up temporarily to a wet nurse, or permanently to another family. The woman herself might in turn become wet nurse to a wealthier family, while using part of her wages to pay her own child's wet nurse.

In pre-modern times, it was incorrectly believed that wet nurses could pass on personality traits to infants, such as acquired characteristics.

Mythology Many cultures feature stories, historical or mythological, involving superhuman, supernatural, human, and in some instances, animal wet nurses. The Bible refers to Deborah, a nurse to Rebekah, wife of Isaac and mother of Jacob (Israel) and Esau. In Greek mythology, Eurycleia is the wet nurse of Odysseus. In Roman mythology, Caieta was the wet nurse of Aeneas. In Burmese mythology, Myaukhpet Shinma is the nat (spirit) representation of the wet nurse of King Tabinshwehti. In Hawaiian mythology, Nuakea is a beneficent goddess of lactation;Native planters in old Hawaii: their life, lore, and environment by Edward Smith Craighill Handy, Elizabeth Green Handy, Mary Kawena Pukui. her name became the title for a royal wet nurse, according to David Malo.Hawaiian antiquities (Moolelo Hawaii) by David Malo

The importance of the wet nurse to ancient Roman culture is indicated by the founding myth of Romulus and Remus, who were abandoned as infants but nursed by the she-wolf, as portrayed in the Capitoline Wolf bronze sculpture. The goddess Rumina was invoked among other birth and child development deities to promote the flow of breast milk.

Ancient Rome

In ancient Rome, well-to-do households would have had wet nurses (Latin , singular ) among their slaves and freedwomen,Keith R. Bradley, "Wet-Nursing at Rome: A Study in Social Relations," in The Family in Ancient Rome (Cornell University Press, 1986), p. 213. but some Roman women were wet nurses by profession, and the Digest of Roman law even refers to a wage dispute for wet-nursing services ().Bradley, "Wet-Nursing at Rome," p. 214. The landmark known as the Columna Lactaria ("Milk Column") may have been a place where wet nurses could be hired.Suzanne Dixon, Childhood, Class and Kin in the Roman World (Routledge, 2001), p. 62; Bradley, "Wet-Nursing at Rome," p. 214. It was considered admirable for upperclass women to breastfeed their own children, but unusual and old-fashioned in the Imperial era.Bradley, "Wet-Nursing at Rome," p. 201. Even women of the working classes or slaves might have their babies nursed,Bradley, "Wet-Nursing at Rome," pp. 201–202 et passim, especially p. 210. and the Roman-era Greek gynecologist Soranus offers detailed advice on how to choose a wet nurse.Soranus of Ephesus, Gynaecology 2.19.24–5. Inscriptions such as religious dedications and epitaphs indicate that a would be proud of her profession.Celia E. Schultz, Women's Religious Activity in the Roman Republic (University of North Carolina Press, 2006), p. 54; Bradley, "Wet-Nursing at Rome," p. 202ff. One even records a , a male "milk nurse" who presumably used a bottle.Evidence for bottle-feeding among the Romans is very slim, and the nutritor may have simply been a nursemaid; Bradley, "Wet-Nursing at Rome," p. 214. Greek nurses were preferred,Soranus, Gynaecology 2.44. and the Romans believed that a baby who had a Greek could imbibe the language and grow up speaking Greek as fluently as Latin.Richard Tames, Ancient Roman Children (Heineman, 2003), p. 11.

India By the 1500s, a wealthy mother who did not use a wet nurse was worthy of remark in India. The child was not "put out" of the household; rather, the wet nurse was included within it. The imperial wet nurses of the Mughal court were given honours in the Turco-Mongol tradition.

United Kingdom

Wet nursing used to be commonplace in the United Kingdom. Working-class women both provided and received wet-nursing services.

Taking care of babies was a well-paid, respectable, and popular job for many working-class women. In the 18th century, a woman would earn more money as a wet nurse than an average man could as a labourer. Up until the 19th century, most wet-nursed infants were sent far from their families to live with their new caregiver for up to the first three years of their life.Wolf, Jacqueline H, "Wet Nursing", Encyclopedia of Children and Childhood in History and Society (2004). As many as 80% of wet-nursed babies who lived like this died during infancy.

During the Victorian era, women took in babies for money and nursed them themselves or fed them with whatever was cheapest. This was known as baby-farming; poor care sometimes resulted in high infant death rates. The wet nurse at this period was most likely a single woman who previously had given birth to an illegitimate child.Acton, W., "Unmarried Wet Nurses", Lancet Vol. 1 (1859): 175. There were two types of wet nurses by this time: those on poor relief, who struggled to provide sufficiently for themselves or their charges, and the professionals, who were well paid and respected.

Upper-class women tended to hire wet nurses to work within their own homes, as part of a large household of servants.

Wet nurses also worked at foundling hospitals, establishments for abandoned children. Their own children would likely be sent away, normally brought up by the bottle rather than being breastfed. Valerie Fildes, author of Breasts, Bottle and Babies: A History of Infant Feeding, argues that "In effect, wealthy parents frequently 'bought' the life of their infant for the life of another."Valerie A. Fildes, Breasts, Bottles, and Babies: A History of Infant Feeding, Edinburgh: Edinburgh University Press, 1986: 193.

Wet nursing decreased in popularity during the mid-19th century, as medical journalists wrote about its previously undocumented dangers. Fildes argued that "Britain has been lumped together with the rest of Europe in any discussion of the qualities, terms of employment and conditions of the wet nurse, and particularly the abuses of which she was supposedly guilty."Valerie A. Fildes, Breasts, Bottles, and Babies: A History of Infant Feeding, Edinburgh: Edinburgh University Press, 1986: 152. C. H. F. Routh, a medical journalist writing in the late 1850s, listed the evils of wet nursing, such as the abandonment of the wet nurses' own children, higher infant mortality, and an increased physical and moral risk to a nursed child.Routh, C. H. F., "On the Mortality of Infants in Foundling Institutions, and Generally, As Influenced By the Absence of Breast-Milk". British Medical Journal 1 (6 February 1858): 105. While this argument was not founded in any sort of proof, the emotional arguments of medical researchers, coupled with the protests of other critics, slowly increased public knowledge; the practice declined, replaced by maternal breastfeeding and bottle-feeding.Valerie A. Fildes, Breasts, Bottles, and Babies: A History of Infant Feeding, Edinburgh: Edinburgh University Press, 1986: 243.

France

Wet-nursing was reported in France in the time of Louis XIV, the mid-17th century. By the 18th century, approximately 90% of infants were wet-nursed, mostly sent away to live with their wet nurses.O'Reilly, Andrea, "Wet Nursing", Encyclopaedia of Motherhood (2010): 1271. In Paris, only 1,000 of the 21,000 babies born in 1780 were nursed by their own mothers. The high demand for wet nurses coincided with the low wages and high rent prices of this era, which forced many women to have to work soon after childbirth. This meant that many mothers had to send their infants away to be breastfed and cared for by wet nurses even poorer than themselves. With the high demand for wet nurses, the price to hire one increased as the standard of care decreased. This led to many infant deaths. In response, rather than nursing their own children, upper-class women turned to hiring wet nurses to come live with them instead. In entering into their employer's home to care for their charges, these wet nurses had to leave their own infants to be nursed and cared for by women far worse off than themselves, and who likely lived at a relatively far distance away.